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WORKS   OF 
PROFESSOR  A.  M.  GREENE,  JR. 

PUBLISHED    BY 

JOHN  WILEY  &  SONS 


Elements  of  Heating  and  Ventilation. 

A  Text-book  for  Technical  Students  and  a 
Reference  Book  for  Engineers.  8vo,  vi  +324 
pages,  223  figures.  Cloth,  $2.50  net. 

Pumping  Machinery. 

A  Treatise  on  the  History,  Design,  Construction, 
and  Operation  of  Various  Forms  of  Pumps. 
8vo,  vi  +703  pages,  504  figures.  Cloth,  $4.00  net. 

Refrigeration  and  Ice  Making,     In  Preparation. 

BY  SPANGLER,  GREENE,  AND  MARSHALL: 

Elements  of  Steam  Engineering. 

Third  Edition,  Revised.  8vo,  v+296  pages, 
284  figures.  Cloth,  $3.00. 


THE    ELEMENTS 

OF 

HEATING  AND  VENTILATION 

A   TEXT-BOOK 

FOR 

STUDENTS,  ENGINEERS  AND  ARCHITECTS 


BY 

ARTHUR   M.    GREENE,    JR. 

Professor  of  Mechanical  Engineering,    Russell  Sage  Foundation,  Rensselaer  Polytechnic 
Institute;  Sometime  Junior  Dean,  School  of  Engineering,  University  of  Missouri 


FIRST    EDITION 

FIRST    THOUSAND 


NEW  YORK 

JOHN    WILEY     &    SONS 
LONDON:   CHAPMAN  &  HALL,  LIMITED 


Copyright,  1912, 

BY 
ARTHUR   M.   GREENE,   JR. 


THE  SCIENTIFIC   PRESS 

ROBERT   DRUMMOND    AND  COMPANY 

BROOKLYN  •  N.    Y. 


PREFACE 


THE  aim  of  the  author  in  preparing  this  book  has  been  to 
bring  together  in  logical  order  and  in  a  small  volume  the 
necessary  data  from  which  to  design  the  heating  and  venti- 
lating systems  of  buildings.  In  doing  this  he  has  been  guided 
by  his  own  experience  in  the  layout  of  such  systems  and  by  the 
previous  works  of  many  authors  which  he  has  used.  He  has 
consulted  these  works  freely,  as  well  as  the  valuable  experi- 
mental data  prepared  by  a  number  of  the  companies  building 
apparatus  for  heating  and  ventilation.  Where  such  work  has 
been  used  credit  has  been  given  to  the  author  or  the  company. 
These  data,  which  in  general  are  scattered  among  various  books 
and  pamphlets  and  must  be  used  by  the  engineer  in  his  work, 
have  been  brought  together  and  placed  in  a  logical  position  in 
a  single  book.  The  data  are  founded  on  careful  experiment 
and  may  be  used  with  confidence.  In  selecting  these  data, 
which  are  given  in  the  forms  of  tables  and  curves,  the  endeavor 
has  been  made  to  include  all  that  are  necessary  to  solve  any 
problem  which  may  arise  in  connection  with  the  warming  of 
buildings  or  the  supply  and  delivery  of  air.  Many  of  the 
curves  and  tables  are  originally  given,  and  in  all  cases  these 
have  been  recomputed  or  redrawn  for  this  book.  Several 
methods  given  for  the  solution  of  problems  are  new. 

The  book  is  intended  for  the  use  of  upper-class  men  in 
technical  schools,  for  engineers,  architects,  and  superintendents 
of  buildings.  All  phases  of  the  work  are  illustrated  by  actual 
problems  for  which  the  slide  rule  has  been  used.  The  use  of 
the  slide  rule  is  recommended  and  advised  for  these  problems. 
Certain  architectural  information  has  been  added  to  aid  those 

iii 

. 259671 


iv  PREFACE 

who  have  not   had  experience  with  constructions  of  various 
forms. 

The  plan  of  the  work  has  been  for  a  continuous  course  of 
study  without  any  omissions.  Each  chapter  forms  a  unit  in 
the  subject  of  heating  and  ventilation.  The  tables  and  curves 
from  commercial  apparatus  are  given  to  aid  in  the  layout  of 
work,  so  that  the  engineer  may  have  in  one  volume  the  neces- 
sary information  for  a  possible  solution.  There  are  many 
different  forms  of  apparatus  which  have  not  been  mentioned  in 
tabular  form  and  these  the  engineer  will  probably  have  in  his 
catalogue  library.  It  is  impossible  to  include  all  in  a  small 
volume.  Those  given  have  been  selected  because  they  repre- 
sent common  forms  in  use. 

The  author  desires  to  thank  his  wife,  Mary  E.  Lewis  Greene, 
for  the  care  she  has  taken  in  the  preparation  of  copy  and  the 
reading  of  proof.  He  desires  to  thank  those  authors  and  manu- 
facturers from  whose  works  he  has  gained  much  as  a  student, 
or  whom  he  has  quoted  in  this  book. 

A.  M.  G.,  Jr. 
SUNNYSLOPE,  TROY,  N.  Y.,  November  26,  1912. 


TABLE   OF   CONTENTS 


CHAPTER   I 

PAGE 

METHODS  OF  HEATING  AND  VENTILATING  BUILDINGS.  .  i 


CHAPTER   II 
AMOUNT  AND  CONDITION  OF  AIR  FOR  VENTILATION 20 

CHAPTER  III 
Loss  AND  GAIN  OF  HEAT 45 

CHAPTER  IV 
RADIATORS,  VALVES  AND  HEAT  TRANSMISSION  FROM  RADIATORS 73 

CHAPTER   V 
METHODS  OF  CALCULATING  HEAT  REQUIRED  FOR  ROOMS 118 

CHAPTER  VI 
DIRECT  STEAM  HEATING 127 

CHAPTER  VII 
HOT-WATER  HEATING 153 

CHAPTER  VIII 
INDIRECT  HEATING . .  I71 


- 


vi  TABLE  OF  CONTENTS 


CHAPTER  IX 

PAGE 

FURNACE  HEATING 237 


CHAPTER  X 
FURNACES  AND  BOILERS 255 

CHAPTER  XI 
DISTRICT  HEATING 279 

CHAPTER  XII 
TEMPERATURE  CONTROL  AND  DRYING  BY  AIR 300 


THE    ELEMENTS  OF   HEATING  AND 
VENTILATION 


CHAPTER  I 
METHODS  OF  HEATING  AND  VENTILATING  BUILDINGS 

THERE  are  several  methods  of  heating  buildings  in  use 
to-day.  For  small  buildings  the  hot-air  furnace  is  quite  com- 
mon. In  this,  as  shown  in  Fig.  i,  the  heat  from  the  burning  of 
coal  is  used  to  heat  air  on  the  opposite  side  of  the  fire  pot  A  or 
radiator  B  through  which  the  hot  gases  pass  on  their  way  to  the 
chimney.  The  heated  air  from  the  dome  or  top  of  the  heater  is 
carried  through  the  leader  pipes  C  to  boots  D  at  the  bottom  of 
the  risers  or  heat  stacks  E.  It  rises  through  the  stacks  to  the 
various  register  faces  F,  where  it  enters  the  rooms  to  be  heated. 
The  air  is  forced  to  rise  through  the  ducts  by  a  difference  in 
pressure  due  to  the  difference  in  the  weight  of  the  hot  air  inside 
and  the  cold  air  outside.  The  cold  air  enters  at  the  bottom  of 
the  heater  casing  at  G,  being  taken  from  the  outside  at  H  or  the 
inside  at  7. 

In  some  house  work  the  foul  air  is  removed  by  vent  stacks 
K  leading  to  the  attic  or  to  a  chimney,  while  in  most  installa- 
tions this  removal  is  cared  for  by  leakage  of  air  from  the  win- 
dows or  doors. 

This  method  of  heating  is  also  a  method  of  ventilation  if 
the  cold  air  or  a  part  of  it  is  taken  from  the  outside. 

Another  common  and  excellent  method  of  heating  is  that 
in  which  radiators,  supplied  with  hot  water  or  steam,  are  placed 
in  the  various  rooms  or  spaces  to  be  heated.  As  shown  in  Fig.  2 


2  ELEMENTS   OF  HEATING  AND  VENTILATION 

the  steam  is  made  or  the  water  is  heated  in  the  boiler  or  heater 
A  from  which  it  is  taken  through  the  distributing  main  or  flow 


FIG.  i. — Hot-air  Furnace  Heating. 

main  B  to  the  various  risers  C  and  thence  to  the  radiators  D  by 
the  connections  E.    The  return  water  or  condensed  steam  known 


HEATING  AND  VENTILATING  BUILDINGS  3 

• 

as  the  return  is  carried  through  branches  F,  return  risers  G  and 
return  main  //  to  the  boiler  or  heater  A.     The  radiators  are 


FIG.  2.— Direct  Heating  by  Steam  or  Hot  Water. 

usually  placed  in  front  of  windows  where  the  up  current  of 
heated  air  will  form  a  blanket  warming  the  cold  air  which  may 


4 


ELEMENTS  OF  HEATING  ANJ  VENTILATION 


enter  around  the  window  and  keep  the  same  from  producing 
cold  currents  or  drafts.     Each  radiator  is  controlled  by  valves 


FIG.  3. — Indirect  System  of  Heating  with  Individual  Stacks. 

on  inlet  and  outlet  side.    This  is  known  as  the  direct  radiation 
system. 


HEATING  AND  VENTILATING  BUILDINGS 


The  indirect  system  of  heating  is  that  in  which  the  radiators 
are  used  to  heat  air  which  is  introduced  into  various  rooms 


FIG.  4. — Plenum  System  of  Indirect  Heating  with  Single  Coil. 

by  riser  stacks  as  in  the  hot-air  furnace  method.    Fig.  3  shows 
this  method  as  applied  to  a  residence  where  natural  circula- 


6  ELEMENTS  OF  HEATING  AND   VENTILATION 

tion  is  depended  on,  while  Fig.  4  shows  one  where  a  fan  blower 
is  used.    This  indirect  system  is  a  combined  method  of  heating 


FIG.  5. — Vacuum  System  of  Ventilation  with  Indirect  Heating  System. 

and  ventilation.    It  is  used  where  definite  ventilation  is  needed 
or  where  it  is  deemed  advisable  to  have  no  radiators  in  the 


HEATING  AND  VENTILATING  BUILDINGS  7 

room.    The  application  of  the  method  of  steam  heating  of  Fig. 
3  is  often  found  in  buildings  of  such  a  size  that  hot-air  furnace 


FIG.  6.  —  Direct  Indirect  System. 


systems  would  not  be  possible  and  yet  it  is  desired  to  bring  the 
heat  in  by  air  with  natural  ventilation.    The  installation  of  an 


8 


ELEMENTS  OF  HEATING  AND  VENTILATION 


indirect  heating  coil  at  the  bottom  of  each  stack  or  group  of 
stacks  makes  this  possible  and  the  positive  steam  circulation 
furnishes  the  heat  to  each  radiator.  The  indirect  system  of 
heating  employing  a  fan  blower  is  found  in  places  where  it  is 
advisable  to  centralize  most  if  not  all  of  the  heating  surface 
in  one  set  of  coils  and  to  make  the  flow  of  air  positive  to  all 
parts  of  the  building  ;  a  fan  blower  is  used  to  produce  a  pressure 
difference.  The  fan  may  be  employed  to  drive  the  air  into  the 
rooms  as  shown  in  Fig.  4,  in  which  case  the  system  is  known  as 
the  plenum  system,  while  in  some  cases  the  air  is  drawn  through 
the  heating  coils  and  into  the  room  by  the  suction  of  a  fan  which 
discharges  the  air  from  the  room  into  the  atmosphere.  The  air 


FIG.  7. — Lamp  Radiators  of  G.  E.  Co. 

in  the  room  is  under  reduced  pressure  and  for  this  reason  the 
system  is  known  as  the  vacuum  system  of  ventilation,  Fig.  5. 

At  times  the  ventilation  of  a  room  is  accomplished  by  con- 
necting the  room  to  the  outer  atmosphere  by  a  series  of  open- 
ings, each  leading  to  a  radiator.  The  radiator  is  so  constructed 
that  a  series  of  flues  is  formed  and  as  the  heated  air  rises 
through  these  flues  cold  air  enters  from  the  outside.  These 
radiators  are  known  as  direct-indirect  radiators  and  as  usually 
constructed,  Fig.  6,  they  are  provided  with  chambers  at  the 
base  which  can  be  used  to  cut  off  the  external  air  when  neces- 
sary and  permit  circulation  from  the  inside. 

The  electric  method  of  heating  has  flexibility,  rapidity,  and 
convenience  in  its  favor,  but  its  great  expense  confines  its  use  to 


HEATING  AND  VENTILATING  BUILDINGS 


9 


special  places  and  for  specific  aims.  Fig.  7  illustrates  a 
luminous  form  of  electric  radiator  for  use  in  removing  the  chill 
from  bathrooms  or  dressing  rooms  where  heat  is  needed  orf* 
short  notice  and  for  a  short  time  only.  The  one  on  the  left  is 
known  as  a  three-glower  luminous  radiator  and  that  on  the 
right,  a  four-glower.  Fig.  8  represents  coil-resistance  radiators 
or  air  heaters  used  on  steamships,  buildings  or  electric  cars,  when 


Wall  Type  Tubular  Electric 
Air  Heater. 


Stateroom  Type  Tubular 
Electric  Air  Heater. 


FIG.  8.— Resistance  Air  Heaters  of  the  G.  E.  Co. 

the  expense  of  operation  and  danger  from  individual  hot  water 
or  hot-air  heaters  makes  this  form  of  heater  practicable. 

The  glower  luminous  radiators  are  made  of  various  capaci- 
ties. Some  of  them  are  made  small  enough  to  be  put  on  a  lamp 
circuit.  These  are  of  500  watts  capacity  and  consist  of  two  glow- 
ers. With  four  glowers  there  are  two  sizes  built,  one  of  1000 
watts  and  one  of  2000  watts.  The  radiators  are  built  for  two 
sets  of  voltages,  95-125  and  200-225.  The  tubular  air  heaters 
shown  in  Fig.  8  are  of  the  wall  type  and  the  stateroom  type. 
They  are  made  to  dissipate  300  and  500  watts  per  tube.  With 


10 


ELEMENTS  OF  HEATING  AND  VENTILATION 


the  first  consumption  there  is  no  danger  of  reaching  a  scorching 
temperature.  In  the  case  of  the  stateroom  heater  the  tubes  are 
separately  controlled  and  a  junction  box  is  shown  to  connect 


u-  y  u 


FIG.  9. — Floor  and  Ceiling  Vent. 

to  the  conduit  system.  The  heating  element  in  these  air  heaters 
is  of  special  form  originally  intended  for  rheostat  work;  in  it  the 
wire  of  special  composition  is  wound  on  a  soft  asbestos  tube,, 


HEATING  AND  VENTILATING  BUILDINGS 


11 


then  fixed  mechanically  and  the  tube  solidified  by  coating  it 
with  a  fireproof  cementing  compound. 

The  manner  of  ventilating  rooms  with  the  various  systems 
of  heating  described  above  has  been  examined,  but  there  yet 
remain  several  systems  for  which  the  accompanying  method  of 
ventilation  has  not  been  described. 

In  many  installations  little  or  no  provision  is  made  for  ven- 
tilation, the  freshening  of  the  air  being  produced  by  leakage 
around  windows  and  doors.  Such  a  method  is  not  reliable  and 
except  for  house  or  office  installation  in  which  there  will  be  few 
occupants  in  large  rooms  it  should  not  be  employed. 


FIG.  10. — Method  of  Ventilation. 

In  some  cases  the  fresh  air  is  supposed  to  enter  from  the 
windows  or  doors  while  the  foul  air  is  taken  out  through  ven- 
tilating ducts  leading  to  the  roof  or  attic.  In  this  case,  Fig.  9, 
there  are  usually  two  registers  leading  to  the  ventilating  ducts, 
one  at  the  floor  and  the  other  at  the  ceiling.  The  air  is  ordi- 
narily taken  from  the  floor  of  the  room,  as  this  will  cause  a 
better  circulation.  The  upper  register  may  be  used  when 
necessary  to  clear  the  room  rapidly. 

When  fresh  air  is  brought  into  the  room  from  a  hot-air 
furnace,  fan  and  heater  or  from  the  heating  box,  this  air  should 
be  delivered  near  the  top  of  the  room  on  its  cold  side  as  shown 
in  Fig.  10.  In  this  way  the  air  is  thoroughly  mixed  arid  there 


12  ELEMENTS  OF  HEATING  AND  VENTILATION 

is  no  chance  for  the  air  to  short-circuit  across  the  room.  If  air 
entered  at  A  and  was  taken  out  at  either  B  or  C  there  would 
be  a  chance  for  ventilating  air  or  in  some  cases  for  the  heating 
air  to  be  carried  out  before  it  had  a  chance  to  either  heat  or 
ventilate  it  and  certain  portions  of  the  room  would  remain 
unprovided  for.  The  supply  on  the  cold  wall  makes  it  possible 
for  down  currents  of  cold  air  to  pass  out  at  the  vent  openings 
before  mixing  with  the  warmer  currents. 

I**  When  vents  alone  are  placed  in  a  room  with  direct  heaters 
these  should  be  placed  on  the  exposed  wall. 

Although  this  method  of  bringing  the  heated  air  in  through 
ducts  on  the  exposed  wall  has  certain  advantages,  the  method 
of  ducts  in  inner  partitions  is  often  employed  because  this 
location  can  be  better  arranged  in  the  construction  of  the  build- 
ing and  the  heat  loss  from  these  can  be  used  to  warm  the  build- 
ing, thus  the  heat  will  not  escape  directly  to  the  atmosphere  as 
may  occur  from  the  outer  walls. 

With  direct  radiation  in  steam,  hot  water  or  electric  heating, 
air  when  introduced  is  for  ventilation  only  and  in  such  cases  the 
air  is  heated  to  the  temperature  desired  for  the  room  and  not 
above  this  temperature,  as  is  the  case  when  the  air  has  to  sup- 
ply the  heat  to  care  for  losses  through  the  walls.  The  air  in 
all  of  these  cases  should  be  introduced  as  described. 

When  the  air  is  used  for  ventilation  only  it  is  brought  to  the 
rooms  by  ducts  at  70°  or  at  the  temperature  of  the  room,  the 
air  being  introduced  as  shown  in  Fig.  4.  In  this  case,  however, 
it  is  customary  to  deliver  the  air  into  a  main  and  to  take 
branches  to  the  various  rooms.  When,  however,  the  rooms  are 
heated  as  well  as  ventilated  by  the  air  it  is  then  necessary  to 
bring  in  the  air  at  such  a  temperature  that  in  giving  up  the  heat 
to  care  for  the  heat  losses  it  is  cooled  to  the  desired  room  tem- 
perature. Since  the  amount  of  heat  for  the  heat  losses  varies 
in  different  rooms  with  an  independent  variation  in  the  amount 
of  ventilation  it  is  necessary  to  bring  air  at  different  tempera- 
tures to  the  various  rooms.  This  is  accomplished  by  having  all 
of  the  air  tempered  to  about  70°  F.  and  then  to  take  a  portion 
of  this  to  a  reheater  and  increase  its  temperature. 


HEATING  AND  VENTILATING  BUILDINGS 


13 


If  now  the  tempered  air  and  heated  air  are  mixed  in  proper 
amounts  any  temperature  from  that  of  the  tempered  air  to  that 
of  hot  air  can  be  obtained.  If  the  hot  air  is  not  mixed  with 
the  tempered  air,  the  highest  temperature  is  reached  while 
tempered  air  alone  will  give  the  lowest  temperature.  This  is 
accomplished  by  separating  the  air  into  two  portions  at  the 
reheater.  If  now  the  tempered  air  and  the  heated  air  are  carried 
in  pipes,  flues  or  ducts  throughout  the  building,  a  two-duct  or 


FIG.  ii.— Hand  Control  of  Mixing  Damper. 

double-duct  system  is  the  result.  In  this  case  two  branches  are 
carried  to  each  riser  duct.  The  damper  at  the  bottom  of  this 
riser  is  hinged  at  the  partition  between  the  two  ducts.  By  rais- 
ing this  damper  by  hand,  Fig.  1 1 ,  or  by  the  thermostatic  motor, 
Fig.  12,  the  air  from  the  top  duct  is  throttled  while  by  lower- 
ing, the  lower  duct  is  cut  off  partially.  In  this  way  the  tem- 
perature of  the  room  into  which  the  air  discharges  may  be 
regulated. 

At  times  this  mixing  is  done  just  beyond  the  heater  as  in  Fig. 


14 


ELEMENTS  OF  HEATING  AND  VENTILATION 


13,  and  in  this  case  separate  lines  of  single  pipes  are  run  from 
this  point  to  the  riser  for  each  line.  This  gives  what  is  known 
as  the  single-duct  system. 


FIG.  12. — Motor  Control  of  Mixing  Damper. 


FIG.  13. — Single  Duct  System. 

The  use  of  the  ozonator  for  the  purpose  of  purifying  the  air 
must  be  mentioned  at  this  point  as  well  as  the  claims  made  by 
certain  physiologists  that  the  mere  circulation  of  air  will  main- 
tain its  power  of  supporting  respiration  until  the  carbon  dioxide 


HEATING  AND  VENTILATING  BUILDINGS 


15 


content  is  much  higher  than  the  amount  usually  allowed.  As 
will  be  mentioned  in  the  next  chapter  many  claim  that  CO2 
is  but  an  indicator  of  the  presence  of  other  impurities.  If  this 
be  so  then  the  circulation  of  air  may  cause  some  of  these  impuri- 
ties to  oxidize  and  in  the  case  of  the  use  of  ozone,  the  breaking 
down  of  Oa  into  62  and  O  give  an  active  nascent  atom  which 
probably  oxidizes  the  impure  emanations  from  the  breath  and 
purifies  the  air.  Experiments  with  ozonators  have  shown  this 
to  be  the  case. 

Fig.  14  gives  a  view  of  the  ozonator  built  by  the  General 
Electric  Co.  This,  for  alternating  currents,  consists  of  an 
electric  motor  and  fan  mounted  on  top  of  the  case  which  con- 
tains a  step-up  transformer  and  six  or  more  ozone  generators. 
If  direct  current  is  supplied  the  motor  is  replaced  by  a  rotary 
converter  which  not  only  drives  the  fan  blower  but  converts 
the  direct  current  into  alternating  current,  so  that  this  may  be 
used  in  the  transformer  to  get  a  sufficiently  high  voltage  to 
produce  a  violet  discharge  but  not  so  high  that  the  discharge 
will  be  intense  enough  to  produce  nitrous  oxide.  The  gen- 
erating units  consist  of  a  number  of 
glass  tubes  coated  on  the  outside  with 
a  metallic  coating  and  having  on  the 
inside  an  aluminum  electrode  com- 
posed of  a  series  of  aluminum  cups 
mounted  on  a  spindle.  The  diameter 
of  the  cups  is  smaller  than  that  of 
the  tube  so  that  there  is  a  small 
definite  air-gap  between  the  electrode 
and  the  tube.  The  exterior  coatings 
are  connected  in  multiple  with  one 
terminal  of  the  high  side  of  the  trans- 
former and  the  electrodes  are  con- 
nected in  multiple  with  the  other. 
The  high  alternating  voltage  induces 
charges  on  the  inside  of  the  tube  and 

a  violet  discharge  takes  place  across  the  gap,  the  energy  of 
which  is  used  in  the  production  of  ozone.  The  blower  on  top 


FIG.  14. — G.  E.  Alternating 
Current  Ozonator. 


16  ELEMENTS  OF  HEATING  AND  VENTILATION 

forces  4000  cu.ft.  of  air  per  hour  through  the  generators  and 
this  charges  the  air  with  six  milligrams  of  ozone  per  cubic 
meter.  To  do  this  requires  about  70  watts  on  A.C.  supply  and 
87  watts  on  B.C.  supply.  There  are  two  switches  on  the  ozonator, 
one  controls  the  whole  apparatus,  the  other,  a  three-point  switch, 
controls  the  voltage  of  the  transformer,  regulating  the  amount 
of  ozone.  The  first  point  gives  four  milligrams  per  cubic 
meter;  the  second  five,  and  the  third  six'.  The  blower  is  always 
in  operation  when  the  first  switch  is  turned  on.  The  trans- 
former may  be  cut  out  by  the  second  switch  at  the  off 
position.  The  ozonator  requires  igf"  in  height  and  has  a 

basenJ"Xi4". 

The  results  obtained  by  the  apparatus  are  remarkable  as 
the  following  quotations  from  the  General  Electric  Bulletin 
4912,  from  which  the  above  description  is  taken,  will  illus- 
trate. 

"Perhaps  one  of  the  most  universal  applications  of  ozone 
will  be  in  the  treatment  of  air  for  the  destruction  and  removal 
of  noxious  odors,  organisms  and  emanations.  This  subject  has 
received  some  attention  in  America  where  the  matter  of  ozone 
application  is  a  new  one,  and  much  attention  in  Europe,  par- 
ticularly in  France,  where  ozone  has  long  been  recognized  as  a 
valuable  agent  of  sanitation. 

"  Ozone  acts  on  the  air  as  a  bactericide  as  well  as  a  power- 
ful agency  of  deodorization.  For  the  purpose  of  studying  the 
power  of  ozone  to  destroy  noxious  odors,  Scoutettin  chose  a 
ward  of  the  hospital  at  Metz,  having  a  magnitude  of  about  noo 
cubic  meters.  In  this  hall  he  placed  two  piles  of  manure  about 
10  meters  apart.  These  manure  piles  were  permitted  to  remain 
48  hours,  during  which  period  the  room  became  filled  with  a 
pernicious  odor  indicating  an  advanced  stage  of  putrefaction, 
as  shown  by  the  evidence  of  the  ammonia  evolved. 

"When  this  had  been  accomplished,  two  vessels  of  8  liters 
capacity  were  opened  in  the  hall,  permitting  their  contents  of 
ozonized  air  to  diffuse  therein.  The  ammoniacal  odor  dimin- 
ished considerably,  though  it  did  not  disappear  completely. 
The  manure  was  then  removed  and  the  experiment  repeated. 


HEATING  AND  VENTILATING  BUILDINGS  17 

This  time  the  odor  disappeared  completely  and  rapidly,  the  nox- 
ious gases,  hydrogen  sulphide,  carbon  bisulphide  and  ammonia 
having  been  destroyed. 

"  Experiments  with  cultures  of  the  tubercular  bacilli  have 
shown  that  these  grow  with  only  one-fourth  the  rapidity 
of  check  cultures,  when  exposed  to  the  action  of  ozonized 
air. 

"  These  results  show  that  where  ozonized  air  comes  in  con- 
tact with  the  living  colonies  their  development  is  impeded; 
but  that  when  the  bacterial  colony  grows  deep  within  the  cul- 
ture medium,  the  action  of  ozone  applied  to  the  surface  only  is 
less  marked,  if  not  altogether  imperceptible. 

"This  is  what  should  be  expected  according  to  Ohlmuller, 
who  has  demonstrated  that  the  bactericidal  action  of  ozone 
is  greatly  interfered  with  in  the  case  of  colonies  growing  on 
organic  matter;  for  the  ozone  oxidizes  the  organic  medium, 
thus  destroying  itself,  before  it  makes  sensible  its  action  on  the 
bacteria.  Ozone  destroys  itself  in  oxidizing  organic  matter 
and  coagulates  albuminous  matter. 

"It  may  be  deduced  from  the  foregoing  that  any  extra- 
neous organic  matter  found  in  air  which  it  is  desired  to  sterilize, 
will  diminish  the  action  of  ozone  by  combining  with  it;  and  in 
consequence,  the  air  should  be  first  filtered  whenever  prac- 
ticable. Many  failures  to  produce  sterilization  in  researches 
on  ozonizing  air  have  resulted  from  the  presence  of  a  relatively 
large  amount  of  organic  matter  in  the  air. 

"Ozone  will  find  an  application  in  the  sterilization  and  deo- 
dorization  of  the  air  of  hospitals,  apartments,  studios,  schools, 
etc.,  wherever  there  is  likely  to  be  large  crowds. 

"In  stables,  chicken  coops,  toilets  and  factories,  where  there 
are  evolved  noxious  emanations,  ozone  will  greatly  ameliorate 
the  conditions.  In  particular,  the  shops  for  assorting  rags, 
manufacture  of  fertilizers  and  factories  which  work  gelatin, 
glue,  hides,  hair,  fat,  bones,  horn  and  other  slaughter-house 
by-products,  and  those  which  are  a  source  of  emanations 
dangerous  to  the  public  health,  will  find  in  ozone  a  powerful 
ally. 


18  ELEMENTS  OF  HEATING  AND  VENTILATION 

"Wherever  pure  sterile  air  is  of  value  in  the  factory  either 
before,  during,  or  after  the  completion  of  the  product,  e.g., 
distilleries,  breweries,  wine  houses,  etc.,  the  use  of  ozone  should 
be  resorted  to. 

"The  Art  Theater  on  State  Street,  Schenectady,  a  moving- 
picture  show,  had  experienced  difficulty  with  its  ventilation. 
The  theater  consists  of  a  hall  about  30  by  100  feet,  and  the  ven- 
tilation is  provided  by  a  suction  blower  capable  of  aspirating 
about  ninety  thousand  cubic  feet  per  hour.  The  management 
were  very  desirous  of  providing  the  best  ventilation  possible, 
as  is  evidenced  by  the  elaborate  and  expensive  system  cited.  It 
was  found,  however,  that  notwithstanding  the  magnitude  of  the 
blower,  '  crowd  odors  '  persisted  in  the  room.  The  blower  was 
as  large  as  could  be  used,  for  anything  larger  would  have  pro- 
duced obnoxious  drafts. 

"As  a  solution  to  the  trouble,  an  ozonator  was  installed  above 
the  front  entrance  to  the  theater,  in  such  a  way  as  to  permit  the 
ozonized  air  to  diffuse  into  the  current  of  ventilating  air  drawn 
toward  the  aspirator.  The  instantaneous  effect  of  this  was 
remarkable.  The  theater  has  been  entirely  deodorized  and 
even  during  the  hottest  weather  of  the  past  summer  the  air 
within  the  theater  has  been  fresh,  cool  and  odorless,  excepting 
for  the  faint  and  rather  pleasant  smell  of  the  slight  excess  of 
ozone. 

"The  next  case  which  we  may  cite  provides  an  even  more 
remarkable  instance  of  the  efficacy  of  ozone  in  deodorizing 
obnoxious  air,  since  this  case  relates  to  a  factory  in  which, 
through  the  nature  of  the  work  carried  on,  emanations  are 
evolved,  which  constitute  a  vehicle  of  certain  volatilized  dilu- 
ents and  solvents  of  the  varnishes  and  adhesives  used.  In  a 
workshop  some  75  feet  by  200  feet  upwards  of  two  hundred 
girls  are  employed  in  the  preparation  of  various  articles  of 
pasted  mica.  It  is  easy  to  realize  that  the  problem  of  providing 
clean  air  under  such  conditions  will  always  be  a  difficult  one, 
and  in  the  present  instance  a  considerable  expenditure  of  money 
and  ingenuity  was  incurred  before  the  correct  solution  was 
found. 


HEATING  AND  VENTILATING  BUILDINGS  19 

"  Finally  two  ozonators  were  installed,  one  near  each  end  of 
the  room,  and  the  windows  which  had  to  be  wide  open  to 
clear  the  air  were  now  only  slightly  open.  A  number  of  other 
instances  are  recorded  in  this  bulletin  showing  the  usefulness 
of  this  apparatus." 


CHAPTER   II 
AMOUNT  AND  CONDITION  OF  AIR  FOR  VENTILATION 

AIR  is  composed  principally  of  nitrogen  and  oxygen  with 
small  quantities  of  carbon  dioxide,  water  vapor  and  the  rare 
element,  argon. 

The  amounts  of  the  various  constituents  are  given  below: 

By  Weight.  By  Volume. 

Nitrogen 75 . 50%  78 . 06% 

Oxygen 23 . 20  21 .  oo 

Argon 1.3  .94 

Approximately  this  is 

Nitrogen 77 .  79 . 

Oxygen 23 .  21 . 

Helium,  metargon,  neon,  krypton,  and  xenon  have  been  dis- 
covered in  air  in  small  but  constant  amounts. 

Free  air  is  found  to  contain  from  3  to  4  parts  of  C02  in 
10,000  parts  by  volume. 

The  amount  of  water  vapor  contained  in  air  varies  with  the 
temperature  and  saturation.  This  vapor  is  not  always  suf- 
ficient to  saturate  the  air  with  vapor.  The  ratio  of  the  amount 
contained  to  that  required  to  saturate  the  air  at  the  temper- 
ature considered  is  called  the  relative  humidity  while  the  actual 
amount  of  vapor  per  cubic  foot  is  known  as  the  absolute  humid- 
ity. Thus  at  75°  F.  air  may  contain  0.00135  Ib.  or  9.5  grains 
of  water  vapor  per  cubic  foot.  This  quantity  will  just  sat- 
urate it.  If  the  air  is  half  saturated  or  the  relative  humidity  is 
50  per  cent  the  quantity  of  water  vapor  is  4.75  grains  to  the 
cubic  foot. 

In  addition  to  the  above  substances  there  may  be  impur- 

20 


AMOUNT  AND   CONDITION  OF  AIR  FOR  VENTILATION     21 

ities  given  off  from  persons  or  processes  and  these  are  variable 
quantities  depending  on  the  particular  place  and  time. 

For  general  work,  the  air  will  be  assumed  to  contain  79 
parts  of  nitrogen  by  volume,  21  parts  of  oxygen,  4  parts  in 
10,000  of  C02  and  a  variable  amount  of  water  vapor. 

The  amount  of  fresh  air  to  be  taken  into  a  room  depends  on 
the  permissible  amount  of  CO2  allowed.  It  is  estimated  that 
20  cu.ins.  of  air  is  inhaled  at  each  respiration  and  there  are  about 
20  respirations  per  minute,  making  about  a  quarter  of  a  cubic 
foot  of  air  per  minute.  The  CO2  in  this  respired  air  amounts 
to  about  4  per  cent  so  that  the  respired  air  has  its  C02  content 
increased  100  fold  from  4  parts  per  10,000  up  to  400  parts. 
Although  the  CCb  is  heavier  than  the  air,  having  a  molecular 
weight  of  44  while  the  air  has  a  weight  of  28.9  it  diffuses  through 
the  air  and  forms  a  mixture  of  air  and  C02.  This  foul  air  is 
then  diluted  by  the  air  in  the  room  and  the  condition  of  the 
air  in  the  room  is  raised  to  x  parts  of  CO2  per  10,000  parts.  If 
V  is  the  volume  of  the  air  allowed  per  person  per  hour,  the 
equation  showing  the  value  x  would  be 


=    xV  ,. 

10000          10000          10000' 

If  the  quantity  of  air  respired  per  minute  is  changed  from 
that  assumed  and  if  the  quantity  of  C02  in  the  exhaled  air  is 
not  4  per  cent  for  actual  conditions,  other  values  can  be  used 
in  the  equation.  .The  equation  reduces  to 

6OOO  N 


or 

V  =  600°  ..........     (3) 

x-4 

Formula  (3)  gives  the  quantity  of  air  per  hour  if  the  allowable 
quantity  in  vitiated  air  x  is  known.  Formula  (2)  gives  the 
quality  of  vitiated  air  if  V  is  known.  According  to  Pettenkofer 


22  ELEMENTS  OF  HEATING  AND  VENTILATION 

the  amounts  of  CO2  per  hour  developed  by  a  strong  workman- 
at  work  is  1.275  cu.ft.  while  at  rest  it  is  only  0.825  cu.ft.  These 
are  higher  than  the  amount  assumed  above.  Scharling  gives 
0.635  cu.ft.  as  the  amount  of  CO2  per  hour  produced  by  men. 
This  agrees  with  the  assumption  made  above.  The  other 
values  of  C02  exhaled  per  person,  given  by  Scharling  are  as. 
follows : 

Women. 0.600  cu.ft.  per  hour 

Young  men 0.614     "      "      " 

Young  women °-455     "      ll      " 

Boys 0.363     "      "      " 

Girls 0.343     "      "      " 

The  presence  of  n  parts  of  CO2  per  10,000  in  air  when  the 
increase  has  been  due  to  respiration  is  found  to  be  oppressive 
and  harmful.  In  cases  of  gatherings  of  healthy  persons  this  may 
reach  15  parts  while  with  sick,  it  should  be  kept  as  low  as  7 
parts.  Some  claim  that  it  is  the  other  gases  or  organic  mat- 
ters which  are  exhaled  which  cause  this  air  to  be  harmful.  The 
lungs  and  the  moistened  mouth  and  nostrils  must  allow  saliva 
and  other  fluids  to  be  discharged  in  the  forms  of  vapors  and 
these  with  any  bacteria  exhaled  contaminate  the  atmosphere. 
It  may  be  that  the  C02  is  merely  an  indicator  of  the  other  harm- 
ful constituents  in  the  atmosphere  of  rooms  which  are  poorly 
ventilated.  When  the  CO2  content  is  about  7  parts  to  10,000 
there  is  no  evidence  of  discomfort  and  this  may  be  taken  as  the 
limit  of  x  for  proper  ventilation.  Eq.  (3)  then  gives 

T7     6000  .  , 

V  =  —  -  =2000  cu.ft.  per  hr. 

7-4 

This  value  is  usually  employed  for  the  proper  ventilation 
of  buildings,  2000  cu.ft  per  person  per  hour.  In  cases  where 
the  number  of  persons  is  not  definite  it  is  customary  to  express 
the  amount  of  air  in 'terms  of  the  number  of  times  the  volume 
of  the  rooms  is  changed  per  hour. 


AMOUNT  AND  CONDITION  OF  AIR  FOR  VENTILATION     23 

Rietschel  recommends  the  following  amounts: 

TABLE  OF  CUBIC  FEET  OF  AIR  PER  HOUR  PER  PERSON 

Max.  Min. 

Hospitals  for  adults 2650  2650 

Hospitals  for  children 1 240  1 240 

Schools,  children  under  10  years 600  353 

Schools,  children  over  10  years 885  530 

Waiting-rooms  with  known  number  of  people  .  . .    1240  706 

Auditoriums  with  unknown  number  of  people ...  2  changes  i  change 

House  rooms  in  constant  use 4  changes  3  changes 

House  rooms  in  occasional  use i  change  |  change 

Kitchens  and  toilet  rooms 5  changes  3  changes 

When  the  number  of  persons  is  not  known  some  designers 
use  the  following  when  provisions  are  made  for  changing  the  air: 

Residences:  Halls,  3  changes 

Sitting  rooms,  and  ist  floor  rooms,  2  changes 
Sleeping  rooms  and  2d  floor  rooms,  i  change 

Stores:  ist  floor,  2  to  3  changes,  2d,  i|  to  2  changes 

Offices:  ist  floor,  2  changes;    2d,  i|  changes 

Churches  and  public  assembly  rooms,  f  to  2  changes 

When  no  provisions  are  made  for  ventilation,  leakage  will 
cause  about  T%-  of  the  above  changes.  Experiments  have  been 
made  to  show  that  this  leakage  actually  does  take  place. 

The  following  allowances  are  to  be  used: 

FOR  ADULTS  PER  HOUR  PER  PERSON 

Hospitals 2400  cu.f t. 

Auditoriums 2000    ' ' 

Workshops 2000    ' ' 

Waiting-rooms 1000    ' ' 

FOR  CHILDREN 

Hospitals 1500  cu.ft. 

Schools 1500-2000    ' ' 

Auditoriums 1500    ' ' 

Workshops 1500    ' ' 

As  gas  flames  give  off  CO2,  moisture  and  other  gases,  the  use 
of  gas  burners  in  a  room  contaminates  the  air  and  requires  addi- 
tional air  for  ventilation.  If  a  gas  contains  by  volume  10  per 
cent  carbon  monoxide,  2  per  cent  carbon  dioxide,  30  per  cent 
methane,  4  per  cent  C2H4  and  the  remaining  gases  do  not  con- 
tain carbon,  it  will  be  found  that  the  burning  of  one  cubic 


24 


ELEMENTS  OF  HEATING  AND  VENTILATION 


foot  of  gas  will  produce  J  cu.ft.  of  CC>2,  if  reduced  to  the  initial 
temperature  and  pressure.  The  amount  of  CO2  exhaled  per 
hour  per  person  equals  4  per  cent  of  the  air  used  which  amounts 
to  about  4  per  cent  of  15  cu.ft.  or  0.6  cu.ft.  The  amount  of  con- 
tamination of  the  ordinary  Welsbach  mantle  burner  using 


FIG.  15. — Pettersson's  CO2  Apparatus. 

3  cu.ft.  equals  that  produced  by  two  persons,  while  the  fish-tail 
burner,  using  5  cu.ft.,  is  equivalent  to  four  persons.  Carpenter 
states  this  thus:  The  burning  of  i  cu.ft.  of  gas  per  hour  re- 
quires the  amount  of  air  equal  to  that  required  for  one  person. 
The  amount  of  C02  in  the  air  in  most  cases  is  so  slight  that 
the  ordinary  gas  apparatus  cannot  be  used  to  determine  it. 
A  form  due  to  Pettersson  is  used.  The  tubes  A,  B  and  C  are 


AMOUNT  AND  CONDITION  OF  AIR  FOR  VENTILATION    25 

immersed  in  a  water  bath  to  equalize  the  temperature.  By 
lowering  and  raising  the  mercury  bottle  D,  the  caustic  potash  is 
sucked  to  the  mark  on  the  capillary  tube  below  the  cock  F  and 
then  tube  A  is  exhausted  of  air  through  the  cock  E.  The  air  to 
be  tested  is  then  drawn  into  A  to  the  small  tube  M  at  the 
bottom  which  is  graduated.  While  this  is  being  done  /  and  H 
are  open.  After  closing  these  and  the  cock  E,  and  bringing 
the  mercury  in  D  and  A  to  the  same  level,  the  cock  G  is  open 
and  the  position  of  the  liquid  drop  at  K  is  noted.  G  is  then 
shut  off,  F  opened  and  the  air  is  driven  over  into  the  burette  C 
where  it  comes  in  contact  with  the  KOH  on  the  glass  tubes,  the 


FIG.  16.— CO2  Bottle. 

KOH  is  driven  into  the  vessel  L.  This  is  repeated  several  times, 
then  the  air  is  driven  into  A  until  the  KOH  fluid  reaches  the 
same  mark  below  F  when  F  is  closed.  G  is  opened  and  D  is  raised 
or  lowered  until  the  drop  K  is  at  the  original  scale  reading. 
This  means  that  the  pressure  on  the  gas  in  A  is  the  same  as 
before.  The  reading  on  the  scale  M  then  gives  the  diminu- 
tion of  volume  or  the  amount  of  C02  absorbed.  The  small 
tube  M  permits  one  to  determine  small  absorptions  and  the 
drop  K  gives  an  accurate  method  of  getting  the  correct  pressure. 
A  simple  apparatus  for  getting  relative  results  is  shown  in 
Fig.  1 6.  The  bottle  is  filled  with  a  standard  solution  of 
sodium  carbonate  and  phenolphthalein.  If  CO2  is  introduced 
into  this  until  there  is  sufficient  to  change  the  sodium  carbonate 


26  ELEMENTS  OF  HEATING  AND  VENTILATION 

into  the  bicarbonate,  the  pink  color  is  destroyed  and  the  solu- 
tion becomes  colorless.  If  now  it  takes  A  volumes  of  the  bulb 
to  destroy  the  color  when  atmospheric  air  is  used  and  ^Volumes 
for  the  same  amount  of  the  same  liquid  when  taking  air  from  a 
room,  the  number  of  parts  per  10,000  in  the  air  of  the  room  will 

be  -^-.    Billings  gives  the  strength  of  solution  to  be  5.3  grams 

£> 

of  desiccated  sodium  carbonate,  i  gram  of  phenolphthalein 
and  1000  c.c.  of  distilled  water  which  has  been  recently  boiled 
and  cooled.  When  ready  to  use,  this  is  diluted  still  further  with 
twenty-five  times  its  volume  of  boiled  distilled  water.* 

The  amount  of  moisture  in  the  air  is  another  important 
item  to  consider  in  connection  with  the  air  for  ventilating  pur- 
poses. If  the  relative  humidity  is  low,  evaporation  will  take 
place  from  the  surface  of  the  body  producing  dry  skin  or  dry 
mucous  membrane  in  throat  or  nose  and  at  the  same  time  the 
temperature  of  the  body  will  be  lowered  due  to  this  evaporation. 
If  on  the  other  hand  the  air  is  saturated  the  body  will  feel  damp 
and  clammy.  In  either  case  the  air  is  objectionable.  The 
usual  amount  of  moisture  to  make  the  room  comfortable  should 
be  such  as  to  give  a  relative  humidity  between  60  per  cent  and 
80  per  cent. 

To  determine  the  amount  of  moisture  in  air,  hygrometers  of 
some  form  are  used.  One  method  is  to  reduce  the  air  or  a  sample 
of  it  to  such  a  temperature  that  it  will  become  saturated  or 
deposit  moisture.  Fig.  17  illustrates  one  form  of  dew-point 
apparatus  or  hygrometer  in  which  the  aspiration  of  air  through 
a  volatile  liquid  reduces  its  temperature  so  that  moisture  begins 
to  form  on  the  silvered  surface  at  the  lowered  end  of  the  appara- 
tus. The  temperature  at  which  this  forms  can  be  noted  and 
again  the  temperature  at  which  the  moisture  just  disappears. 
The  mean  gives  the  temperature  of  saturation  or  the  dew-point. 
The  weight  of  moisture  (or  steam)  per  cubic  foot  at  this  tem- 
perature, from  the  steam  tables  gives  the  quantity  of  moisture 
present  per  cubic  foot  at  actual  temperature.  This  will  be  the 

*  Lunge  to  whom  this  method  is  due  does  not  find  the  exact  proportion 
and  gives  a  proportional  table  of  number  of  volumes  of  bulb  and  amount  of  CO2. 


AMOUNT  AND  CONDITION  OF  AIR  FOR  VENTILATION     27 


amount  of  moisture  per  cubic  foot  in  the  original  air  except  for 
the  slight  reduction  of  volume  due  to  the  change  of  absolute 
temperature;  hence  if  the  weight  of  steam  for  the  given  tem- 
perature of  the  original  air  is  divided  into  the  actual  weight 
the  result  is  the  relative  humidity. 

This  form  of  apparatus  is  difficult  to  use  and  for  that  reason 
the  wet  and  dry-bulb  hygrometer  is  used.  This  consists 
of  two  thermometers  on  one  of  which  a  piece  of  wet  wi eking 


FIG.  17. — Dew  Point  Apparatus. 


FIG.  1 8. — Sling  Psychrometer. 


encases  the  bulb.  As  water  is  evaporated  from  this  wicking 
the  temperature  is  lowered  and  the  thermometer  reads  lower 
than  the  dry-bulb  thermometer.  This  action  is  not  regular 
if  the  thermometer  or  air  is  at  rest  and  hence  the  II.  S. 
Weather  Bureau  recommends  whirling  these  thermometers. 


28  ELEMENTS   OF  HEATING  AND  VENTILATION 

Fig.  1  8  shows  the  appearance  of  this  type  of  instrument.  It  is 
sometimes  called  a  sling  psychrometer. 

Experiments  have  been  made  comparing  readings  of  the  dry 
bulb  and  difference  between  wet  and  dry  bulb  with  the  relative 
humidity  readings  obtained  by  a  dew-point  apparatus.  From 
these  Ferrel  has  reduced  for  the  U.  S.  Weather  Bureau  the 
following  formula: 

p  =  pi-o.ooo^B(t-ti)[i  +0.00064(^1  -32)].      .     (4) 

In  this  expression  p  is  the  pressure  of  the  water  vapor  at  the 
dew  point,  pi  the  pressure  at  the  temperature  of  the  wet  bulb, 
B  the  barometric  pressure,  /  the  temperature  of  the  dry  bulb  in 
degrees  Fahrenheit  and  t\  the  temperature  of  the  wet  bulb  in 
the  same  units,  p,  pi  and  B  are  measured  in  the  same  units, 
pounds  per  square  inch,  inches  of  mercury  or  by  other  unit.  This 
formula  contains  the  quantity  B  and  hence  all  humidity  charts 
and  tables  based  on  the  formula  are  worked  out  for  the  standard 
atmospheric  pressure  of  29.92  ins.  of  mercury  and  corrections 
must  be  applied  for  other  barometric  pressures.  If  p  is  found  by 
this  formula,  the  weight  of  steam  per  cubic  foot  at  this  pressure 
and  temperature  may  be  found  from  the  steam  tables.  The 
number  of  cubic  feet  of  air  for  a  given  weight  at  the  temperature 
t  will  be  greater  than  that  at  the  dew  point  /d,  and  therefore  the 
steam  will  occupy  more  space.  If  Wsp  is  the  weight  of  a  cubic 
foot  of  steam  at  the  dew  point,  the  weight  in  a  cubic  foot  at 
the  temperature  /  will  be 


/+45Q-6 

In  the  above  the  air  pressure  is  practically  constant.  If  W* 
is  the  amount  of  'steam  per  cubic  foot  required  to  saturate 
the  volume  at  the  temperature  /,  the  relative  humidity  will  be 
given  by 


" 


Now  since  the  pressure  p  is  the  partial  pressure  due  to  the 


AMOUNT  AND   CONDITION   OF  AIR  FOR  VENTILATION    29 

moisture  present,  the  ratio  of  this  to  the  saturation  pressure 
will  give  the  same  value  practically  or 


relative  humidity  =  — (7) 

P* 


150 


Difference  between  Wet  and  Dry  Bulb 
42°  38'   34°  30°    26°24       20°     16°       12°10°  8°  6° 


30 


0.20 


0.40  1         0.60 

Relative  Humidity 


0.80 


1.00 


FIG.  19. — Relative  Humidity  and  Moisture  for  30.3  ins.  Barometer. 

Diagrams,  Figs.  19  to  22,  give  relative  humidities  and  weight 
of  moisture  per  cubic  foot  of  air  in  grains  figured  from  this 
formula  for  barometric  pressures  of  29.1  ins.,  29.5  ins.,  29.9  ins., 
30.3  ins.  of  mercury.  Another  instrument  shown  in  Fig.  23, 


30 


ELEMENTS  OF  HEATING  AND  VENTILATION 


known  as  the  hydrodeik  (as  made  by  the  Taylor  Instrument 
Co.)  employs  a  graphical  chart  by  which  relative  humidity 
and  other  psychrometric  data  can  be  obtained. 

The  sliding  pointer  on  the  arm  pivoted  at  the  top  is  set 


Difference  between  Wet  and  Dry  Bulb 
48"     40°36°320  28°    24°     20°      16°       13°  10°  8°     6°   4°     2°- 


0.20 


0.40  1        0.60 

Relative  Humidity 


0.80 


1.00 


FIG.  20. — Relative  Humidity  and  Moisture  for  29.9  ins.  Barometer. 

opposite  the  reading  of  the  wet  bulb  and  is  then  swung  over 
until  it  intersects  the  lines  running  down  from  the  dry-bulb 
readings.  These  are  in  red  on  the  apparatus.  The  reading  at 
the  bottom  of  the  pointer  will  then  be  the  relative  humidity. 
The  heavy  black  lines  running  up  from  the  dry-bulb  side  give 


AMOUNT  AND   CONDITION  OF  AIR  FOR  VENTILATION     31 


the  dew  point  if  the  one  passing  from  the  point  of  intersection 
of  the  pointer  with  the  down  line  from  the  dry  bulb  is  followed 
down  to  the  dry  side.  At  the  upper  end  of  these  lines  where 
they  cut  the  down  line  from  120°  F.  will  be  found  the  number 


150 


130 


110 


Difference  between  Wet  and  Dry  Bulb 
50°       40°  36°   32°28°24°    20018°16014°12°10a    8°    6°  4°     2°— 


70 


50 


30 


7i 


£ 

20g 


15 


0.20 


0.40  1         0.60 

Relative  Humidity 


0.80 


LOO 


FIG.  21. — Relative  Humidity  and  Moisture  for  29.5  ins.  Barometer. 

of  grains  per  cubic  foot.  The  Lambrecht  Polymeter  is  an 
instrument  consisting  of  a  number  of  human  hairs  connected  to  a 
pointer  which  gives  the  humidity  because  the  quantity  of  moist- 
ure which  they  will  absorb  and  therefore  the  amount  they  will 
change  in  length  is  a  function  of  the  humidity  of  the  medium 


32 


ELEMENTS  OF  HEATING  AND  VENTILATION 


around  them.    This  instrument  should  be  checked  constantly 
if  used. 

W.  H.  Carrier  has  discussed  the  matter  of  psychrometric 
formulae  in  the  Journal  of  the  American  Society  of  Mechanical 


150 


Difference  between  Wet  and  Dry  Bulb 
48°     40°  36C32°  28°     24°     20°      16°      12°  10°  8°  6°    4°    2— 


0.40  1         0.60 

Relative  Humidity 

FIG.  22. — Relative  Humidity  and  Moisture  for  29.1  ins.  Barometer. 

Engineers  for  Nov.,  1911  (p.  1311),  and  shows  that  the  tem- 
perature of  the  wet  bulb  is  such  that  the  lowering  of  the  air  and 
water  vapor  in  the  atmosphere  to  this  temperature  will  liberate 
sufficient  heat  to  vaporize  the  necessary  moisture  to  saturate 
the  air  at  the  wet-bulb  temperature.  This  means  that  the 


AMOUNT  AND  CONDITION  OF  AIR  FOR  VENTILATION    33 


wet-bulb  temperature  will  be  above  the  dew  point.  Carrier 
states  that  this  wet-bulb  temperature  depends  on  the  total  of 
the  sensible  and  latent  heat  in  the  air  and  is  independent  of 
the  relative  proportions.  Using  this  fact  Carrier  gives  the 
following  for  i  Ib.  of  air,  mixed  with  W  Ibs.  of  water; 


FIG.  23.— Hydrodeik. 
Heat  given  up  in  cooling  air  and  moisture 

=  (iXCpa+CpsXW)(t-t').      . 
Heat  received  by  water  at  temperature  of  wet  bulb 

=  r'(Wf-W). 


Cpa  =  specific  heat  at  constant  pressure  of  air 

=  0.24112  +O.OOOOO9/ ; 
Cps  =  specific  heat  at  constant  pressure  of  steam 

= 0.4423 -[-o.oooiS/  (approximately); 


.     (8) 
(9) 


34  ELEMENTS   OF  HEATING  AND  VENTILATION 

/  =  temperature  of  air  or  dry  bulb; 
/'  =  temperature  of  wet  bulb  ; 
W  =  weight  of  moisture  per  pound  of  air  to  saturate  air 

at  temperature  t'  '; 
r'  =  heat  of  vaporization  of  steam  at  temperature  /'. 

These  may  be  equated  giving 

(Cpa+CvsW)(t-tf}=r'(Wf-W).    -.    .  '  .     (10) 

This  equation  is  based  on  the  theory  that  the  heat  content 
of  the  air  remains  constant  and  has  the  advantage  of  the  empir- 
ical equation  of  Ferrel  which  does  not  hold  for  high  temperatures 
which  are  obtained  in  kiln  or  drying  sheds. 
Solving  the  Eq.  (10)  for  W  gives 


r'W  -C^t-t')  . 

r'+Cps(t-t') 


This  equation  can  be  used  to  solve  for  W  the  moisture  content 
when  t  and  /'  are  known,  for  the  other  quantities  can  be  found. 
It  is  to  be  noted  that 


H//-  53-35  xy  +459-6)  ,    . 

~~75      *,/\  T/  i    .....     V12/ 

144  (B-p)Vt 

Vt  =  volume  of  i  Ib.  of  saturated  steam  at  temperature  t' 
(B—pr)  =  Partial  pressure  on  air  in  pounds  per  square  inch. 

If  W  and  W  are  known  the  drop  in  temperature  due  to 
saturating  the  air  is  given  by 


The  amount  of  water  to  be  absorbed  is  given  by 


AMOUNT  AND  CONDITION  OF  AIR  FOR  VENTILATION    35 
Carrier  in  addition  to  these  derives  the  theoretical  formula: 

, 


2800  —  1.32 

where  t  and  /'  are  the  dry-  and  wet-bulb  readings  and  pf  is  the 
pressure  of  the  saturated  steam  for  the  temperature  t'  ,  B  is  the 
barometric  reading. 

On  account  of  the  error  in  the  thermometer  readings  of  the 
ordinary  sling  psy  chrome  ter,  Carrier  makes  1.6  per  cent  cor- 
rection, giving  the  equation 


..       ..... 

2755-1.28*" 

to  be  applied  with  sling  psychrometer.     If  pt  is  the  saturation 
pressure  at  the  temperature  /,  the  relative  humidity  is 


\ 


2755-1.28*'* 


Either  Ferrel's  or  Carrier's  method  can  be  used  with  agreement 
of  2  per  cent  or  3  per  cent  until  high  temperature  and  large 
temperature  differences  between  wet-  and  dry-bulb  readings  are 
found. 

The  value  of  the  hygrometer  and  the  psychrometric  for- 
mulae resulting  from  it  is  in  the  information  it  gives  us  of  the 
amount  of  water  vapor  contained  in  the  air  and  hence  its  con- 
dition for  use  in  a  ventilating  system  or  for  other  service.  If 
for  instance  air  partially  saturated  is  brought  in  contact  with 
water  finely  divided,  an  evaporation  will  immediately  take  place, 
which  will  cool  the  air  to  practically  the  temperature  of  the  wet 
bulb  of  the  hygrometer.  If,  on  the  other  hand,  cold  saturated 
air  is  warmed  in  a  heater  or  by  a  steam  coil,  the  moisture  con- 
tained in  the  cold  air  is  not  sufficient  to  saturate  the  warm  air 
and  the  unpleasant  sensation  of  excessively  dry  air  is  produced 
unless  the  air  is  humidified  in  some  way. 

Air  which  is  very  warm  may  be  cooled  in  some  processes  and 


36  ELEMENTS  OF  HEATING  AND  VENTILATION 

the  capacity  for  water  vapor  may  be  much  less  than  the  actual 
quantity  contained  at  the  higher  temperature  and  hence  this 
reduction  of  temperature  will  cause  a  precipitation.  By  finding 
the  number  of  pounds  of  water  vapor  per  cubic  foot  from  steam 
tables  at  a  given  temperature,  the  result  may  be  compared  with 
the  capacity  at  another  temperature  and  the  relative  humid- 
ity, quantity  of  vapor  to  be  added  or  abstracted,  or  other  prop- 
erty of  the  vapor  at  the  new  temperature  found. 

The  pressure  exerted  by  the  water  vapor  is  equal  to  the 
steam  pressure  at  the  temperature  considered  as  given  by  any 
set  of  steam  tables.  This  is  usually  known  as  vapor  tension. 
If  the  air  is  not  saturated,  the  pressure  is  equal  to  that  of  the  sat- 
urated vapor  multiplied  by  the  relative  humidity.  Thus  if 
ps  =  pressure  of  saturation  and  p  =  the  relative  humidity,  the 
vapor  pressure  p  is  given  by 


(18) 


A  similar  formula  may  be  used  to  find  the  weight  of  water 
vapor  yr  in  i  cu.ft.  of  air,  namely 

Tv=pys.       ...     .     .     .     .     .     (19) 

Now  the  volume  of  i  Ib.  of  air  is  given  by  the  equation 

_  53-35  X  (/+45Q.6) 

' 


where  va  =  volume  of  i  Ib.  of  air  in  cubic  feet; 
t  =  temperature  of  air  in  degrees  F.  ; 
B  =  barometric  pressure  in  pounds  per  square  inch; 
p  —  partial  pressure  of  moisture  in  pounds  per  square  inch. 

Hence  the  weight  of  moisture  associated  with  i  Ib.  of  air  is 


,     , 

(22) 


ry 

144(5  - 
and  ps  depend  on  /. 


AMOUNT  AND   CONDITION  OF  AIR  FOR  VENTILATION     37 


On  account  of  y  being  such  a  small  quantity  when  expressed 
in  pounds,  this  may  be  reduced  to  grains  by   multiplying  by 

7000. 


150 


Difference  in  Temperature 
50      42    38    34  3Q        26       22     18      14.12    10 


4      2 


'02468  1.0 

Relative  Humidity 

FIG.  24. — Relative  Humidity  and  Moisture  According  to  Carrier's  Formula. 


These  formulae  for  the  weight  of  moisture  in  the  air  in  grains 
are  = 

W  (per  cu.ft.)=7ooopYs  =  7oooY«, (23) 

W  (per  Ib.  dry  air)  =  7oooX53.35(<+459.6)p*      ^ 


38 


ELEMENTS  OF  HEATING  AND  VENTILATION 


The  relative  humidity  p  and  the  partial  pressure  p  may  be 
found  by  the  charts  or  the  formulae  and  after  these  are  known 
the  weight  of  moisture  may  be  found  for  any  given  condition. 

To  aid  in  computing  problems  relating  to  moisture,  the 
curves,  Figs.  19,  20,  21,  22  and  24  are  given,  the  first  four 
using  the  Weather  Bureau  formula,  the  last,  from  Carrier's 
article  in  the  Journal  of  American  Society  of  Mechanical  Engin- 
eers. Table  I  is  constructed  to  give  certain  of  this  information 
in  tabular  form. 

TABLE  I 

PROPERTIES  OF  DRY  AIR  AND  AIR  SATURATED  WITH  MOISTURE 


H 

<    . 
§PH 
cn 

Weight 

Vapor  Tension 
or 
Steam  Pressure.* 

Partial  Pressure 
on  Air. 

Weight  of  Water 
Vapor  in   i   Cubic 
Foot  of  Mixture. 

Weight 
of  Air  in 

Pounds 

^  Q> 

of 

i  Cubic 

of  Mois- 

3& 

i  Cubic 

Foot  of 

ture   Per 

SLf 

Foot  of 

Pounds 

Pounds 

Mixture 

Pound 

eQ 
£ 

Dry  Air. 

Per 

Square 

Inches 
Mercury 

Per 
Square 

Inches 
Mercury 

Pounds. 

Grains. 

in 
Pounds. 

of  Air. 

H 

Inch. 

Inch. 

O 

0.0863 

0.019 

0.038 

14.678 

29.873 

0.00008 

0.6 

0.0862 

0.0009 

IO 

0.0845 

0.031 

0.063 

14.666 

29.858 

O.OOOI2 

0.8 

0.0843 

0.0014 

20 

0.0827 

0.050 

0.103 

14.647 

29.818 

0.00019 

1-3 

0.0825 

0.0023 

30 

0.0810 

O.oSl 

0.164 

14.616 

29-757 

0.00029 

2.O 

o  .  0805 

0.0036 

40 

0.0794 

O.  122 

o  .  248 

14-575 

29-673 

0.00041 

2.9 

0.0788 

0.0052 

50 

0.0779 

0.178 

0.362 

14.519 

29-559 

0.00059 

4-1 

0.0762 

0.0077 

60 

0.0765 

0.256 

O.52I 

14.441 

29.400 

o  .  00083 

5-8 

0.0752 

O.OIIO 

70 

0.0749 

0.363 

0.739    !  14-334 

29.182 

0.00115 

8.0 

0.0731 

0.0157 

80 

0-0735 

0.506 

I  .030    1  14.191 

28.891 

0.00158 

ii  .1 

0.0710 

0.0226 

90 

0.0722 

0.696 

I.4I7 

14.001 

28  .  504 

0.00213 

14.9 

0.0688 

0.0310 

IOO 

0.0709 

0.946 

I  .926 

I3-75I 

27-995 

0.00285 

19.9 

o  .  0663 

o  .  0430 

no 

'0.0697 

I  .  271 

2-588 

13.426 

27-333 

0.00377 

26.4 

0.0636 

0.0592 

120 

0.0685 

1.689 

3-439 

13.008 

26.482 

0.00493 

34-5 

o  .  0606 

0.0814 

130 

0.0673 

2.  22O 

4.520 

12.477 

25.401 

0.00637 

44-6 

0.0571 

o.  1115 

140 

0.0662 

2.885 

5-873 

11.812 

24  .  048 

0.00814 

57-0 

0.0532 

°-I53i 

150 

0.0651 

3-7I5 

7-563 

10.982 

22.358 

0.01032 

72.2 

o  .  0486 

O.  2122 

• 

1  60 

o  .  0640 

4.738 

9.646 

9-959 

20.275 

0.01296 

90.7 

0.0434 

0.2987 

170 

o  .  0630 

5-990 

12.195 

8.707 

17.726 

0.01613 

112.9 

0.0373 

0.4320 

1  80 

0.0620 

7-510 

15.289 

7.187 

14.632 

0.01993 

!39-5 

o  .  0303 

0.6571 

IQO 

0.0611 

9-339 

19.013 

5.358 

10.908 

0.02444 

171.1 

0.0223 

1.0974 

200 

o  .  0602 

11.528 

23.469 

3.169 

6.452 

0.02974 

208.2 

0.0130 

2.2930 

*  From  Peabody's  Tables  and  Marvin's  Results. 


AMOUNT  AND   CONDITION  OF  AIR  FOR  VENTILATION     39 


HUMIDIFIERS  AND  WASHERS 

Another  important  consideration  is  that  of  the  cleanliness 
of  air  for  ventilation.  Air  from  the  atmosphere  near  a  large  city 
is  laden  with  dust  particles  which  will  be  introduced  into  build- 
ings, where  they  collect  on  furniture,  tapestry,  walls  or  on  goods 
in  the  process  of  manufacture.  Moreover  this  air  is  not  good 
for  breathing  and  hence  endeavor  is  made  to  cleanse  it  before 
discharging  it  into  the  rooms. 

Several  methods  have  been  proposed  for  this  purpose.    Fig. 


FIG.  25. — Carrier  Air  Washer  and  Humidifiers. 

25  shows  that  of  the  Buffalo  Forge  Co.,  The  Carrier  Air  Washer 
and  Humidifier.  After  the  air  passes  the  tempering  coils  it 
enters  a  chamber  in  which  are  placed  a  number  of  nozzles  from 
which  on  account  of  the  rapid  rotation  of  water  within  the 
nozzle  a  spray  is  formed  which  fills  the  chamber.  As 
air  is  drawn  through  this  spray,  it  collects  the  dust  particles 
and  part  of  them  fall  to  the  bottom  of  the  chamber  with  the 
water.  A  large  part  of  the  moisture  and  dust  particles  are 
carried  over  to  a  series  of  vertical  plates  which  are  arranged  so 
that  the  air  has  to  take  a  zigzag  course.  In  this  way  the  mois- 
ture is  collected  and  runs  down  the  surface  of  the  plates  to  a 
reservoir  at  the  bottom  from  which  it  is  taken  from  a  settling 


40 


ELEMENTS  OF  HEATING  AND  VENTILATION 


chamber  through  a  strainer  to  a  centrifugal  pump  by  which 
it  is  again  taken  to  the  nozzles. 

The  Eliminator  plates  are  so  arranged  with  projections  that 
the  water  cannot  be  carried  along  by  the  air.  In  this  way  the 
air  leaves  the  eliminator  without  a  trace  of  free  moisture.  The 
collection  of  dust  and  dirt  may  be  washed  out  from  the  collect- 
ing chamber  at  intervals. 

The  degree  to  which  this  air  is  tempered    before    passing 


FIG.  26. — Warren  Webster  Washer  and  Humidifier. 

through  the  washer  and  humidifier  should  be  such  that  the 
moisture  content  is  that  desired  for  air  to  be  used  in  the  various 
rooms.  If  this  air  is  too  hot  its  moisture  content  will  be  so  great 
that  moisture  will  condense  on  being  used  at  room  temperature. 
Fig.  26  shows  the  method  used  by  Warren  Webster  &  Co. 
in  their  air  washer  and  humidifier.  In  this  apparatus  water  is 
discharged  from  a  pipe  A  at  the  top  of  the  air  passage  just 
beyond  the  tempering  coils.  This  pipe  is  perforated  with  holes 
arranged  in  a  line  but  inclined  to  each  other.  The  discharge  from 
these  holes,  re  in.  or  larger  in  diameter,  strikes  against  a  copper 


AMOUNT  AND  CONDITION  OF  AIR  FOR  VENTILATION     41 

hood  as  shown.  This  makes  the  water  fall  in  a  sheet  of  crossing 
streams,  the  hood  causing  each  individual  jet  to  spread  out 
lengthwise  of  the  pipe.  The  pipe  A  is  supplied  from  one  end  by  the 
pipe  B  and  at  the  other  by  the  equalizer  pipe  C,  which  crosses 
over  the  apparatus.  The  valves  on  the  pipes  B  and  C  are  so 
arranged  that  water  may  be  sent  through  the  spray  pipe  from 
one  end  only,  the  water  passing  from  the  other  end  through  the 
equalizing  pipe  to  D  and  then  to  the  sewer.  In  this  way  the  dirt 
which  may  clog  up  the  spray  pipe  can  be  cleaned  out.  The  ends 
of  the  spray  pipe  or  head  are  carried  by  deflecting  plates  which 
keep  the  water  from  coming  in  contact  with  the  casing  and  so 
eroding  it.  After  passing  a  short  distance  from  the  second  sheet 
of  water  the  air  enters  the  eliminators  or  baffles  E,  the  window 
F  opening  into  the  space  in  front  of  the  baffles.  The  eliminator 
consists  of  two  rows  of  V-shaped  plates  slightly  inclined  to  the 
horizontal  so  that  the  water  and  dirt  abstracted  from  the  air 
may  drain  off  at  one  end.  These  two  rows  are  found  sufficient 
to  remove  the  excess  moisture.  The  main  portion  of  the  dirt 
is  removed  by  the  sheet  of  spray  and  falls  to  the  bottom  where 
a  metal  tank  is  placed.  From  this  point  the  water  passes  through 
a  double  strainer  to  the  suction  of  the  centrifugal  pump  and  is 
again  discharged  through  A .  A  float  valve  is  used  in  the  system 
to  make  up  the  loss  of  water  to  the  air.  An  overflow  and  a 
drain  are  connected  with  the  sewer  for  the  purpose  of  removing 
the  dirt  at  intervals.  In  some  Warren  Webster  apparatus 
spray  nozzles  are  used  in  addition  to  the  spray  head. 

In  most  of  this  apparatus  it  is  well  to  preheat  the  air  to  40° 
or  50°  so  as  to  prevent  the  formation  of  ice  in  cold  weather, 
and  secondly  to  have  such  a  temperature  that  the  saturation 
of  the  air  at  that  point  will  give  the  proper  relative  humidity 
at  the  temperature  of  the  building.  The  Warren  Webster 
purifier  has  also  a  device  attached  to  it  such  that  water  is 
heated  to  about  the  temperature  of  the  tempered  air,  thus 
making  the  air  practically  saturated  at  the  temperature  fixed 
by  the  tempering  coils.  This  temperature  is  controlled  by 
a  thermostat  placed  in  the  space  just  in  front  of  the  reheating 
coil.  By  finding  the  temperature  of  the  air  saturated  with  vapor 


42 


ELEMENTS  OF  HEATING  AND  VENTILATION 


at  which  the  amount  of  water  vapor  is  equal  to  that  desired  in 
the  heated  air  the  thermostat  is  set  at  this  temperature  and  then 
steam  will  be  admitted  to  heat  the  air  and  water  until  this 
temperature  is  obtained. 


FIG.  27.— Cloth  Filter. 


FIG.  28. — Whitley  Patented  Air  Filter. 

In  Figs.  27  and  28  simple  methods  of  cleaning  the  air  are 
shown.  A  cheese  cloth  fabric  is  placed  around  a  wire  cylinder, 
closing  off  the  inlet  of  a  fan  blower.  The  air  is  drawn  through 
this  and  deposits  its  dust  or  dirt.  The  dirt  is  washed  from  the 


AMOUNT  AND  CONDITION   OF  AIR  FOR  VENTILATION    43 

cloth  by  revolving  the  cylinder  in  a  trough  of  water  by  which 
it  is  washed  clean.  In  Fig.  28  the  cloth  is  folded  over  sticks 
and  is  hung  in  folds  between  the  edges  of  a  box.  The  air  in 
passing  through  the  cloth  gives  up  the  dirt.  In  both  of  these 
the  endeavor  has  been  to  make  the  cloth  surface  as  large  as 
possible  to  cut  down  the  velocity. 

The  air  washer  becomes  an  apparatus  for  cooling  the  air 
in  the  summer  time  if  the  humidity  of  the  atmosphere  is  low, 
as  the  evaporation  of  the  water  vapor  will  cool  the  air.  It 
practically  reduces  the  air  to  the  temperature  of  the  wet  bulb 
of  a  hygrometer.  If  the  air  is  saturated  with  moisture,  there 


0.80 
*: 

|o.ro 

^ 

0.60 
0.5Q. 

V 

X 

\ 

X 

\ 

^ 

-^ 

^fc^*"*»i 

-•  —  . 

-  —  . 

^-^ 

*—  «= 

, 

—  —  , 

"      _ 

- 

—  ~—  — 

• 

—  ^— 

W°            50°              00°             70°             80°             90°            100J           110*            120°            13 
Temperature  of  Inlet  Air 

FIG.  29. — Values  of  K  for  Various  Temperatures. 

will  be  no  decrease  in  temperature  unless  the  water  used  in  the 
washer  is  low.  In  such  a  case  fresh  cold  water  from  the  city 
supply  or  a  deep  well  is  passed  through  the  washer  and  dis- 
charged directly  into  the  sewer  after  falling  to  the  bottom.  In 
this  way  the  water  is  not  heated  as  would  occur  if  this  were 
used  repeatedly.  This  method  of  cooling  is  an  important  one  for 
summer  ventilation.  Warren  Webster  &  Co.  have  experimented 
with  their  apparatus  and  give  a  series  of  curves  showing  the 
amount  of  cooling  in  air  of  various  temperatures  and  various 
relative  humidities  when  using  the  water  repeatedly  and  when 
using  cold  water  at  various  temperatures,  allowing  the  water  from 
the  apparatus  to  waste  to  the  sewer.  The  author  has  shown  the 


44  ELEMENTS  OF  HEATING  AND  VENTILATION 

results  of  their  work  as  an  approximate  formula.     When  the 
water  is  recirculated  the  drop  in  temperature  is  given  by 


(25) 


where  ta  =  temperature  of  the  air  in  degrees  F.; 
twt>  =          "  "  wet  bulb  in  degrees  F. 


K  is  a  constant  depending  on  the  temperature  of  the  air  and  is 
given  by  the  curve  Fig.  29  AJr  =  drop  in  temperature  of  air.  When 
cold  water  is  used  and  then  wasted,  the  drop  is  given  by 


(26) 

24L  2 


=  temperature  of  water  in  degrees  F. 


CHAPTER  III 
LOSS  AND    GAIN   OF    HEAT 

HEAT  being  a  form  of  energy,  may  be  measured  in  any  unit 
of  energy.  In  the  United  States  and  other  English-speaking 
countries  it  is  customary  to  measure  it  in  British  Thermal 
Units.  (B.t.u.)  A  British  thermal  unit  is  the  amount  of  heat 
required  to  heat  i  Ib.  of  water  from  62°  F.  to  63°  F.  Of 
recent  years  some  authors  prefer  to  use  the  mean  B.t.u.,  which 
is  rlir  of  the  heat  required  to  raise  the  temperature  of  i  Ib.  of 
water  from  32°  F.  to  212°  F.  The  second  or  mean  B.t.u.  is 
equal  to  1.003  B.t.u. 

The  French  use  the  Calorie,  the  amount  to  raise  i  kg.  of 
water  from  15°  C.  to  16°  C.  or  TOTF  ef  the  amount  to  raise  i  kg. 
from  o°  C.  to  100°  C. 

By  experiment  the  relation  of  these  units  with  the  other 
units  of  energy  have  been  determined  and  are  given  below  with 
certain  other  transformation  constants: 

i  B.t.u.  =  778  ft.-lbs. 
i  B.t.u.  =0.998  mean  B.t.u. 
i  B.t.u.  =0.252  calories 
i  calorie  =  426. 6  kg.m. 
i  calorie  =  3. 968  B.t.u. 
i  ft.-lb.  =0.1383  kg.m. 
i  kg.m.  =  7.2330  ft.-lbs. 
i  kg.  =  2.2046  Ibs. 
i  lb.=  0.4536  kg. 
i  m.  =39.37  in. 
i  m.  =3. 2808  ft. 
i  ft.  =0.3048  m. 
i  sq.ft.  =0.09290  sq.m. 

45 


46  ELEMENTS  OF  HEATING  AND  VENTILATION 

i  sq.m.  =  10.7639  sq.ft. 
i  cu. ft.  =0.0283  cu.m. 
i  cu.m.  =35.31  cu.ft. 
i  atmosphere  =  14.696  Ibs.  per  sq.in. 
=  29.921  ins.  mercury 
=  760  mm.  mercury 
=  10,333  kg.  per  sq.  meter 
i  kg.  per  sq.cm.  =  14.22  Ibs.  per  sq.in. 
i  watt  hour  =  3.41  B.t.u. 

=  2652  ft.-lbs. 
i  cu.  liter  of  mercury  =  13. 5959  kg. 

i  horse-power  =  5  50  ft.-lbs.  per  sec. 

=  33,000  ft.-lbs.  per  min. 
=  746  watts 

i  horse-power  hour  =  2546  B.t.u. 
i  inch  of  mercury  =  0.491 2  Ibs.  per  sq.in. 
i  inch  of  water  =  0.036  Ibs.  per  sq.in. 

=  0.58  oz.  per  sq.in. 
i  oz.  per.  sq.in.  =  1.72  inches  of  water 
i  U.  S.  gallon  =  231  cu.in. 

The  heat  loss  from  rooms  is  made  up  of  several  parts.  There 
are  radiation  and  conduction  from  walls,  windows  and  doors  and 
convection  losses  due  to  warming  of  the  leakage  air  or  the  air 
for  ventilation.  The  gain  of  heat  is  derived  from  persons  or  appa- 
ratus used  in  the  room  or  from  sources  of  light  of  various  kinds. 

The  loss  of  heat  through  walls  partakes  of  the  nature  of 
radiation  and  conduction.  The  principal  loss  is  made  up  of 
transmission  which  is  found  to  depend  on  the  difference  of 
temperature  and  therefore  it  is  similar  to  conduction  rather 
than  radiation  which  depends  on  a  higher  power  of  the  tem- 
peratures. The  general  form  in  which  this  heat  loss  is  given  is 

H  =  KA(ti-t0))       .    .     ....     (27) 

where  A  =  area  in  square  feet ; 

K  =  Heat  transmitted  per  square  foot  per  hour  per  degree 
difference  of  temperature  in  B.t.u.; 


LOSS  AND  GAIN  OF  HEAT 


47 


ti  =  room  temperature  in  degrees  F. ; 
t0  =  outside  temperature  in  degrees  F.; 
Z7  =  B.t.u.  transmitted  per  hour. 


The  value  of  K  depends  on  several  factors:  the  surface, 
thickness,  and  kind  of  material,  air  spaces  and  condition  of  air 
at  surface.  The  following  German  method  from  H.  RietscheFs 
Leitfaden  zum  Berechnen  und  Entwerfen  von  Lliftungs-und 
Heizungs-Anlagen  is  useful  for  future  reference  for  cases  which 
have  not  been  calculated  in  the  text. 

The  rate  of  transmission  of  heat  through  any  substance 
depends  on  the  thickness  and 
on  the  difference  of  tempera- 
ture. If  for  instance  the  wall 
shown  in  Fig.  30  is  made  up 
of  several  thicknesses  and  the 
temperatures  are  those  marked, 


the  equations  for  the  trans- 
mission of  heat  through  each 
section  must  each  give  the 
quantity  of  heat  transmitted 


FIG.  30.— Wall  Section. 


by   the  wall   and   these,    therefore,    must    be    equal   to    each 
other. 

The  amount  of  heat  conducted  by  any  material  per  square 
foot  of  cross-section  varies  directly  with  the  temperature  differ- 
ence and  inversely  with  the  length.  This  gives 


(28) 


where  C  is  the  constant  of  conduction  for  i  foot  thickness  in 
B.t.u.  per  square  foot  per  degree,  /  is  the  thickness  in  feet  and 
/i—  /2  is  the  difference  of  temperature.  Using  this  for  the  wall 
shown  in  Fig.  30  the  following  results: 


.       .       (29) 


48 


ELEMENTS  OF  HEATING  AND  VENTILATION 


At  the  surface  of  any  material  there  is  to  be  found  a  temper- 
ature different  from  that  of  the  space  around  and  it  is  this  dif- 
ference which  determines  the  flow  of  heat  at  the  surface.  If 
a  is  the  coefficient  of  transmission  per  square  foot  per 
hour  per  degree  across  the  surface  this  becomes  at  different 
surfaces : 


(30) 


The  values  of  H  in  the  sets  above  are  all  the  same,  hence 
solving  for  temperature  differences  and  adding,  the  following 
results: 


H    Hl\     H    H    Hlz    Hlz    H 

—  r-^rH  ---  1  ---  \—^--\—^r-\  — 

(l\        Cl        02       03        C2         C3        04 


Now 


hence 


1  _i_^  _j_  *  _L  T    1^2   ,fe   ,   i 
--  TTrH  ---  1  ---  TTT+TrH  — 

di       Cl       02       03       C2       Cs       04 


K- 
* 


(31) 


K  = 


(32) 


01       02 


The  values  of  Ci,  C2,  €3  are  found  for  different  substances. 
They  are  the  amounts  of  heat  transmitted  for  unit  thickness 
of  material  per  hour  per  square  foot  of  surface  per  degree.  The 
experimental  values  given  by  Rietschel  are  quoted  below  in 
B.t.u. 


LOSS  AND   GAIN  OF  HEAT  49 

VALUES  or  C. 

Air,  still  ..............................  0.03 

Brass  ................................  61  .  oo 

Brickwork  ............................  o  .  46 

Building  paper  ........................  o  .  08 

Cement  ..............................  o  .  40 

Copper  ...............................  202  .  oo 

Cork  .................................  0.17 

Cotton  ...............................  o  .  03 

Felt  .................................  0.02 

Glass  ................................  o  .  54 

Lead  .................................  20  .  oo 

Limestone  ...........................  1.35 

Marble  (fine)  .........................  i  .88 

Mortar  and  plaster  ..............  .  .....  o  .  46 

Oak.  .  ...............................  0.13 

Pine  (along  the  grain)  .......  ...........  o.  n 

Pine  (across  the  grain)  .................  o  .  06 

Plaster  of  Paris  .......  ................  o  .  34 

Sandstone  ...........................  0.87 

Sawdust  ..............................  o  .  03 

Slate  .................................  0.19 

Terra  Cotta  ...........................  o.  54 

Tin  ..................................  35-6o 

Zinc  .................................  74.00 

The  values  of  the  quantities  ai  are  of  the  form  as  given  from 
Grashof  and  Rietschel, 

....     .'(33) 


IOOOO 

d  and  e  are  constants,  d  depends  on  the  condition  of  the  air 
around  surface  and  e  depends  on  the  material.  T  is  the 
temperature  difference  between  the  air  and  the  wall  at  any 
point. 

To  determine  the  quantity  T  a  method  of  approximation  is 


50  ELEMENTS  OF  HEATING  AND  VENTILATION 

used  until  by  practice  one  knows  what  to  expect.    The  value 
of  the  term  involving  Ty 


42d+$ie 

I 0000         ' 


is  small,  hence  for  a  first  approximation  this  term  may  be 
neglected  and  the  value  of  the  various  a's  may  be  found.  These 
then  may  be  used  to  find  K, 


(34) 


After  this  is  known,  the  following  results: 

K(ti  —  to)  ~ di (ti  —  ti)  =  #2(^2  —  t2r)  f    \ 

=  aiTt  =  a2T  =etc  J       '     '     ' 

since 

T  =  /,-//  or  to" -t0. 

These  equations  give  the  first  approximation  for  T. 

In  this  way  after  T  is  found  as  a  first  approximation  the 
value  may  be  used  to  determine  a  second  value  of  a  and  then  a 
new  value  of  T.  In  this  way  two  or  three  trials  will  lead  to  the 
correct  result. 

In  any  case  the  value  of  T  is  small  and  this  particularly  is 
true  for  thick  walls  or  cases  in  which  /<  — 10  is  a  small  quantity. 

Rietschel  gives  results  used  in  practice  for  the  value  of  T  for 
masonry  walls.  These  may  be  put  into  the  form  of  an  equation. 

r=i6.2-4.oo/.     .     ,     ...   .     ,     .     (36) 

This  may  be  used  for  masonry  walls  with  air  spaces  where  I 
is  the  sum  of  the  various  thicknesses,  although  this  result  is 
slightly  too  large  in  this  case  as  the  quantity  K(ti  —  t0)  is  smaller 
than  for  a  solid  wall  of  the  combined  thickness. 

For  a  single  glass  T  is  taken  as  |(/<  — 0  while  for  double 
windows  J(^~0  is  taken  at  each  surface.  Since  glass  is  so 


LOSS  AND  GAIN  OF  HEAT  51 

thin  there  is  practically  no  temperature  drop  in  it.     This  will 
be  seen  later. 

The  value  of  T  for  wooden  floors  is  given  as  T  =  i.&°  F. 
The  values  of  d  as  given  from  Grashof  are  as  follows: 

VALUES  OF  d. 

Air  at  rest  as  in  rooms  or  channels 0.82 

Air  with  slow  motion  as  over  windows i .  03 

Air  with  quick  motion  as  outside  of  building     i .  23 

The  values  of  the  coefficient  e  are  determined  by  Rietschel 
as  follows : 

VALUES  OF  e. 

Brass,  polished o .  05 

Brickwork  and  masonry o .  74 

Cast  iron,  new 0.65 

Cotton o .  75 

Charcoal 0.71 

Copper o .  03 

Glass o .  60 

Mortar  and  lime  mortar o .  74 

Paper 0.78 

Plaster  of  Paris o .  74 

Polished  sheet  iron o .  092 

Rusted  iron o .  69 

Sawdust 0.72 

Sheet  iron . 0.57 

Silk 0.76 

Tin o .  045 

Water 1.07 

Wet  glass i .  09 

Wool 0.76 

Zinc o .  049 

Wood o .  74 

To  explain  the  application  of  the  above,  the  wall  given  in 


52 


ELEMENTS  OF  HEATING  AND  VENTILATION 


Fig.  31  will  be  investigated.  The  wall  is  composed  of  4  ins. 
of  sandstone,  18  ins.  of  brick  work,  a  2-in.  air  space,  8  ins.  of 
brick  and  i  in.  of  plaster.  Where  sections  of  the  wall 
actually  come  in  contact,  there  is  no  surface  resistance  and 
the  wall  may  be  considered  as  solid  except  for  differences  in 
the  values  of  C  for  the  various  materials.  To  find  a  the 


FIG.  31.—  Wall  Section. 

various  values  of  T  must  be  known;  now  T  is  given  by  the 
following  : 

r,  =/<-//; 

T3  =fe"-fe; 

rf  4  4     f  . 

3    =£3  —  J3  , 

T     —f"—f 

I  c    —to     —  h> 

These  quantities  vary  inversely  with  the  different  values  of  a, 
since 


As  the  quantities  a  do  not  differ  by  great  amounts  these  various 
values  of  T  are  considered  as  equal  quantities  in  comput- 
ing a. 

T  may  then  be  found  f:*om  the  equation, 


T  =16.2  —  4.001. 


LOSS  AND  GAIN  OF  HEAT  53 

In  this  case  the  total  thickness  is  31  ins.  and 


(42X1.23+31X0.74)6 

1 0000 

(42X0.82+31X0.74)6 

IOOOO 

(42X0.82+31X0.74)6 

IOOOO 

(42X0.82+31X0.74)6 


04=1.23+0.74+ 


03=0.82+0.74+ 


02=0.82+0.74+ 


ai=o.82+o.74  +  IOQOO 

04  =  2.01; 

03  =  1.59  =  02  =  01. 

K  is  then  found  as  follows: 


K  = 


8.066 


,124. 


2.01       1.58       1.58   '    1.58    '     .87     '    .46    '     .03     '  0.46    '     .46 

I 

0.497+0.633+0.633+0.633+0.718+3.26+0.56  +  1. 

I 


For  a  floor  or  ceiling  as  shown  in  A,  Fig.  32,  the  method  is 
quite  the  same.  When  the  high  temperature  is  at  the  top, 
however,  there  is  no  circulation  in  the  air  space  between  the 
plaster  and  the  floor  and  the  air  acts  as  an  insulating  material. 

When  the  high  temperature  is  below  or  if  the  air  space  is  in 
a  vertical  position  the  circulation  of  the  air  transmits  heat  by 
convection  and  the  air  does  not  act  as  an  insulating  material 
as  was  the  case  with  the  wall  just  considered.  In  any  case, 
however,  there  is  a  resistance  at  the  surface  between  the  air 
and  the  partition  due  to  the  drop  T. 


54 


ELEMENTS  OF  HEATING  AND  VENTILATION 


When  the  same  constant  does  not  hold  over  a  complete 
wall  or  floor  owing  to  a  change  in  the  construction  as  occurs  at 
studs  in  a  partition  or  at  joists  in  a  floor,  the  value  of  K  for  the 
whole  surface  is  found  thus: 


or 


K(Ai+A2)(tt-to)=K1Ai(ti-t 


K 


2KA 


(37) 


.  . 


LathamL 
.Haster 


A       ti" 
FIG.  32.— Wood  Floor  Construction. 

In  most  cases  the  areas  A  have  a  common  dimension  so  that  the 
areas  are  proportional  to  the  widths.  If  these  are  bi  and  b2 
there  results  (Fig.  32), 


bi+b2 


(38) 


The  mean  constant  is  not  usually  found  for  a  wall  in  terms  of 
the  glass  and  wall  coefficient  as  these  are  kept  separate,  but  there 
is  no  reason  why  this  could  not  be  done  as  is  the  case  with 
the  coefficient  for  partitions  with  partition  studs  in  the  cases 
below. 


LOSS  AND  GAIN  OF  HEAT  55 

WTith  the  high  temperature  above  the  air  acts  as  an  insulating 
substance  and  the  following  results  for  the  floor,  Fig.  32,  A: 


42X0.82+31X0.74 
,  =  0.82+0.74+ L  1.8  =  1.57, 


at  joists, 


KJ-—  -  =0.05, 

*     ,     13-25     ,  5  ,     i 

i!57     12X0.06    8X12X0.46     1.57 


at  space  between  joists, 


Ka  = =.027. 

1    +          7          +  2    +      I2      +          3          +          5  ,     i 


1.57    12X8X0.06    1.57    12X0.03    8X12X0.06    8X12X0.46    1.57 

Combined 

^3x0.05+13x0.027 

16 

With  the  high  temperature  below  on  account  of  the  convection 
currents,  the  air  does  not  act  as  an  insulating  substance  and  the 
folio  wing  results: 

^•  =  0.05; 

Ka  = =0.22; 

4     ,       1-25       , 

-    -p- 


• __l       ^  I       v 

1.57    12X0.06    8X12X0.46 
v    3X0.05+13X0.22 

K  =  ^-        i.-  =0.I9. 


This  method  may  be  used  for  various  kinds  of  walls  and  par- 
titions. The  following  values  have  been  computed  by  the  author 
and  these  values  compared  with  those  given  by  Kinealy, 
Rietschel  and  others. 


56  ELEMENTS  OF  HEATING  AND  VENTILATION 

VALUES  OF  a. 
For  brick  and  plaster  or  masonry: 

Outside  a=i.23+o.74+43Xl-23+3lXO-74r 

10000 

=  1.97+0.00757 
=  2.09-0.037, 
since 

7=i6.2-4/. 
Inside,  0  =  1.56+0.00577 

=  1.65— O.O23/. 

For  wood  and  approximately  for  paper,  cotton,  wool,  sawdust, 
charcoal : 

Outside,       0=1.97+0.00757=1.98. 
Inside,          0  =  1.56+0.00577  =  1.57. 

For  glass: 

Outside,       0  =  1.83+0.0077 


-2.07(7--^ -35°). 


Inside  with  motion . 

0=1.63+0.0067 
-1.83  (J-35). 

Inside  without  motion : 

0  =  1.42+0.0057 

Inside  with  motion  and  wet  from  condensation: 

0  =  2.n+o.oo87 
=  2.39. 

For  double  windows: 

Outside,       0  =  i  .95  (7  =  J  X  70) 
Center,        0  =  1.51. 
Inside  dry,  0  =  1.74. 


LOSS  AND  GAIN  OF  HEAT 


57 


'.3 


58  ELEMENTS  OF  HEATING  AND  VENTILATION 

Before  proceeding  with  the  tabular  values  an  explanation 
will  be  made  of  the  various  common  forms  of  building  construc- 
tion which  are  to  be  found  in  the  following  figures. 

Walls.  Walls  are  built  in  many  cases  of  brick.  Bricks  vary 
in  size  in  different  localities.  In  some  places  the  dimensions 
are  8|X3JX2j.  A  standard  8|X4X2|  was  adopted  by  the 
national  Brickmakers'  Association.  These  are  built  in  various 
thicknesses.  At  times  an  air  space  is  made  in  the  wall  as  shown 
in  E,  Fig.  33,  so  that  the  interior  of  the  wall  will  be  dry  and  also 
that  the  wall  will  be  a  better  non-conductor  of  heat.  When  a 
solid  wall  is  built  it  is  not  advisable  to  put  the  plaster  directly 
on  the  wall  as  in  B,  Fig.  33,  because  the  water  soaking  through 
the  wall  will  produce  a  damp  surface.  To  prevent  this  the 
wall,  C,  Fig.  33,  is  furred  before  the  plaster  is  put  on.  This 
consists  in  placing  wood  or  iron  furring  strips  on  the  wall 
and  attaching  wood  or  metal  lath  to  these.  The  wood  strips 
are  usually  f  by  2  ins.  so  that  the  laths  are  removed  about 
|  in.  from  the  wall,  thus  giving  an  air  space.  The  furring  strips 
are  attached  to  wooden  wedges  or  plugs  driven  into  the  joints 
in  the  walls.  The  same  effect  is  obtained  by  the  use  of  hollow 
bricks,  known  in  some  localities  as  "  Haverstraw  bricks,"  as  the 
lining  of  the  wall.  These  are  shown  at  D,  Fig.  33.  Walls  are 
sometimes  faced  with  stone  as  shown  at  F,  Fig.  33.  A  recent 
method  of  wall  construction  for  residences  and  small  buildings 
is  to  use  hollow  partition  tile  and  face  them  with  brick  or  plaster 
as  shown  in  C,  Fig.  40. 

Stone  and  concrete  walls  are  used  for  buildings  and  constants 
have  been  computed  for  these. 

Wooden  walls  or  frame  constructions  are  used  at  certain 
times.  In  this,  studs,  usually  of  2  by  4  in.,  3  by  4  in.,  or  4  by  6 
in.  timbers,  are  placed  upright  at  i6-in  centers,  and  on  these  are 
nailed  sheathing  boards,  which  may  be  planed  boards,  although 
at  times  shiplap  as  shown  in  D,  Fig.  34,  or  tongued  and  grooved 
boards,  E,  Fig.  34,  are  used  to  make  tight  joints  for  the  purpose 
of  keeping  down  the  loss  of  heat.  Building  paper  of  one  or  two 
thicknesses  is  then  placed  on  top  and  the  clapboards  F,  or 
shingles  G,  are  placed  on  top  of  this.  On  account  of  the  frequent 


LOSS  AND   GAIN  OF  HEAT 


59 


vertical  joints  in  the  shingles  these  are  usually  placed  so  that 
not  over  one-third  of  the  length  of  the  shingle  is  exposed  to  the 
weather.  A  represents  a  wall  without  plaster  while  B  and  C 
are  plastered  on  the  interior. 

Floors.     Floors    for    dwellings    and    many    small   buildings 


FIG.  34.— Wooden  Walls. 

are  built  as  shown  in  Fig.  32.  In  this  form  wooden  joists  are 
placed  on  i6-in.  centers  and  on  top  of  them  a  floor  is  built 
composed  of  one  or  two  layers  of  tongued  and  grooved  floor 
boards  or  the  lower  layer  may  be  of  shiplap  or  square  edged- 
boards.  In  any  case  at  least  one  side  of  the  boards  must  be 
planed  to  bring  the  boards  to  a  uniform  thickness.  To  the 
lower  side  of  the  joist,  laths  are  attached  and  these  carry  the 


60 


ELEMENTS   OF  HEATING  AND  VENTILATION 


plaster.  Mill  or  slow-burning  construction,  Fig.  35,  consists  in 
using  heavy  wooden  girders  (12  by  12  ins.)  about  8  ft.  apart 
and  on  these  is  a  floor  of  3-in.  planks.  The  planks  are  usually 
of  yellow  pine  above  which  is  placed  a  hardwood  floor  covering, 


FIG.  35. — Mill  or  Slow-burning  Construction. 

separated  by  building  paper  of  some  kind.  Fig.  36  shows  a 
fireproof-floor  construction  using  reinforced  cinder  concrete  be- 
tween I-beams.  The  cinder  concrete  encases  the  beams.  This  is 
reinforced  by  metal,  resting  on  the  beams.  The  ceiling  below 


mm 


FIG.  36. — Reinforced  Concrete  Floor. 

is  carried  on  metal  laths  attached  to  small  channel  irons  running 
from  beam  to  beam  when  a  flush  ceiling  is  desired,  while  at 
times  the  plaster  is  attached  directly  to  the  concrete,  when 
a  panel  effect  is  desired.  On  top  of  the  reinforced  concrete  a 
lean  cinder  concrete  fill  is  made  between  the  dovetailed  sleepers 


LOSS  AND  GAIN  OF  HEAT 


61 


to  which  the  floor  boards  are  attached.     The  sleeper  usually 
runs  at  right  angles  to  the  beams.     Two  thicknesses  of  floor 


:   v  .  .  v 

•?:l-  -*  •'••'>'  Q  :: ••?     t> "••>'. ::-.":i; '•"--. a : . •-• --'4 ••;•. K  :.  :*  ••.••«:.:.••'  :;v>:.y. 


FIG.  37. — Brick  Arches. 

boards  are  used,  the  upper  surface  being  of  maple  when  lasting 
qualities  are  required. 

Fig.  37  illustrates  methods  of  using  arch  bricks  with  concrete 


FIG.  38.— Hollow  Tile  Flat  Arch. 

filling.  The  end  voussoirs  or  skew  backs  are  specially  made  or 
cut.  The  brick  voussoirs  are  spoken  of  as  rowlocks  when  used 
this  way. 

Fig.  38  exemplifies  the  method  used  with  hollow  fireproofing 


62 


ELEMENTS  OF  HEATING  AND  VENTILATION 


tile.  The  tiles  are  made  to  form  a  flat  arch.  The  cement 
mortar  is  arranged  in  grooves  to  increase  the  bonding  of  the 
tiles. 

A    metal  lath  and  plaster  ceiling  hung  from  a  reinforced 
concrete  roof  is  shown  in  Fig.  39. 


A— Book  Tile. 


S$$^^  Z3 


B— Roof  Tile. 


FIG.  39. — Roof  and  Roof  Ceiling  Tile. 

Fig.  39,  A,  illustrates  a  book  tile  and  B,  a  government  tile, 
used  in  forming  fireproof  roofs.  The  book  tiles  are  placed  so 
that  the  rounded  projecting  edges  fit  into  the  hollowed  edges  of 
the  adjacent  tiles,  the  square  corners  resting  on  the  flanges  of 


LOSS  AND  GAIN  OF  HEAT 


63 


T-irons  which  are  supported  by  or  form  the  purlins  of  the  roof. 
The  tiles  are  3  by  12  by  17!  ins.  long.  The  government  roofing 
tiles  2\  by  12  by  15^  ins.  rest  in  the  T-irons,  the  depressed  edges 
being  so  arranged  that  the  bottom  of  the  tile  is  flush  with  the 
bottom  of  the  irons. 

Partitions.  The  horizontal  section  of  the  ordinary  forms 
of  partitions  are  shown  in  Fig.  40.  A  represents  the  standard 
form  of  wood  partition  made  of  2  by  4  ins.  or  by  3  by  4  ins. 
studs  of  spruce  or  hemlock  placed  on  i6-in.  centers  to  which 


A  B  CD 

FIG,  40, — Partitions, 

are  fastened  wooden  or  metal  laths  or  a  patented  sheet  substance 
known  as  plaster  board,  over  which  plaster  is  placed. 

Form  B  consists  of  a  single  row  of  fireproof  tile  with  plaster 
on  each  side  and  C  shows  two  sets  of  tiles  with  an  air  space 
between  them.  E  gives  a  partition  formed  of  wire  lath  attached 
to  channel  irons  and  D  gives  one  in  which  expanded  metal  is 
used  to  support  the  plaster  while  the  space  on  the  inside  is 
filled  with  asbestos  to  kdeaden  the  sound,  as  well  as  to  cut 
.down  air  currents  and  thus  cutting  down  heat  transmission. 
The  plaster  coat  in  most  cases  takes  up  f  in.  and  this  may  be 
used  in  figuring  thicknesses.  The  above  figures  represent 


64 


ELEMENTS  OF  HEATING  AND  VENTILATION 


various  typical  methods  of  building  construction,  and  the  trans- 
mission coefficients  which  are  computed  for  them  will  serve  as 
guides  for  other  constructions  if  time  is  not  available  for  com- 
puting K. 

VALUES  OF  K. 

WALLS  AND  PARTITIONS 

(See  Fig.  33) 


Combined 
Thickness  of 
Brickwork. 

A. 

B. 

C. 

D. 

Ei. 

E2. 

F. 

4"  

0.55 

0.51 

0.28 

8" 

O.  3Q 

o.  37 

o.  24 

O    2O 

o  27 

o  26 

O    32 

I2"  

0.31 

0.29 

o.  20 

o.  24 

O.  22 

O    22 

O    2O 

16"  
20"  

0.25 
O.  21 

0.24 

O.  21 

0.18 
o.  16 

0.20 

0.18 

O.IQ 

o  17 

O.I9 
O    17 

0.17 

QIC 

24" 

o  18 

o  18 

o  14. 

o  16 

O    I  ^ 

O    1C 

O    14. 

28"  

o.  16 

o.  16 

0.13 

o.  14 

013 

O    13 

O    12 

32".  . 

0.15 

0.14 

O.  12 

o.  13 

O.  12 

O.  12 

0.  12 

MASONRY 

(Fig.  33) 


Masonry  Thickness. 

A. 

B. 

C. 

12"            

O    CA 

O     CT 

o  28 

18" 

O    AC 

O   4.3 

02  C 

24" 

O    30 

O    37 

O    23 

30"  .  . 

O    34 

O    32 

O    21 

36" 

O    3O 

o  28 

O    IO 

48"  

o  24 

O    23 

O    17 

CONCRETE 

(Fig.  33) 


Concrete  Thickness. 

A. 

C. 

12" 

O  4.8 

o  26 

!8"             

o  38 

O    24. 

24" 

O    31 

O    21 

3o" 

O    27 

O    IO 

36" 

O    24. 

O    17 

48" 

O    10 

O    I  c 

LOSS  AND  GAIN  OF  HEAT 


65 


WOODEN  WALLS 
Fig.  34- 


|  Fig.  A,  0.31 
Fig.  B.  0.20 
Fig.  C,  0.08 


PARTITIONS 

(Fig.  40) 

Fig.  A.  Plaster,  one  side o .  49 

Fig.  A.  Plaster,  two  sides o .  36 

Fig.  B ( 0.30 

Fig.  C 0.21 

Fig.  D 0.21 

Fig.  E 0.34 

FLOORS  AND  CEILINGS  AND  ROOFS 


Heated  Room 
Above. 

Heated  Room 
Below. 

f        With  plaster  
j         Without  plaster 

0.031 
O    33 

0.19 
O    33 

Flg>32]         With  plaster  

o  030 

o  16 

1  ^     Without  plaster  

O.  23 

O    23 

Fig.  3  <  . 

o  16 

o  16 

Fig.  36  .  . 

o  02  s 

O    I  £ 

Fig.  37  

O    2< 

O    2S 

Fig.  38.  . 

o  029 

O    14 

Fig.  39.  With  ceiling  

O    22 

Fig.  39.  Without  ceiling  

O   42 

Book  tile  with  wood  sheathing 

O    2  ? 

Fig.  39.  Government  tile  with  wood  sheathing.  .  .  . 

O    3C 

Shingle  roof,  with  no  sheathing  

O.A2 

Shingle  roof,  on  sheathing  

O    31 

Glass 

j  Dry 

o  96 

Single    window  (f  )  |  Wet 

I    IO 

Double  window  (f  ')  

0.41 

Single  skylight    (j")  

I  06 

Double  skylight  (£")  

o.  t;i 

Doors  . 
|"  doors  
i"  doors 

o-SS 

0   4.8 



i^"  doors  

o  40 

2"  doors. 

O    "34. 

The  area  A  of  the  conducting  and  radiating  walls  or  parti- 
tions is  found  from  the  plans  of  the  buildings.  The  total  area 
of  each  side  of  the  room  is  first  found  and  these  are  kept  separate 


66  ELEMENTS  OF  HEATING  AND  VENTILATION 

and  called  north  wall,  east  wall,  south  wall  and  west  wall.  The 
glass  and  door  area  in  each  of  these  walls  is  found  and  the  results 
added  together.  This  sum  is  subtracted  from  the  wall  area  and 
then  the  difference  is  known  as  net  wall  area.  The  door  area  is 
considered  to  be  equal  to  a  window  in  radiating  value  because 
of  its  repeated  opening  and  closing.  The  author  usually  takes 
the  full  window  frame  area  as  window  area  in  making  these 
computations.  This  allows  for  the  loss  of  heat  due  to  leakage 
around  the  frames.  The  floor  and  ceiling  areas  are  also  com- 
puted at  this  point  for  the  determination  of  heat  losses. 

Temperatures  of  Rooms  and  Atmosphere.  In  figuring  /* 
and  t0,  the  temperatures  on  the  two  sides  of  a  wall,  it  is  well  to 
remember  that  the  use  for  which  the  room  is  intended  fixes  one 
of  these  and  if  the  wall  is  an  outside  one  the  other,  t0,  is  fixed 
by  the  lowest  temperature  which  may  continue  for  several  days 
or  for  a  week.  In  the  latitude  of  northern  New  York  t0  may  be 
taken  as  o°  F.  or  it  may  be  — 10°  F.,  while  in  New  York  City, 
10°  F.  or  20°  F.  may  be  used.  In  Washington  20°  F.  or  30° 
F.  might  be  used.  In  most  contracts  the  specifications  call  for 
sufficient  installation  to  heat  the  building  to  a  desired  temper- 
ature in  zero  weather,  but  it  seems  that  this  should  not  be  used 
in  design  unless  zero  weather  is  found  for  several  consecutive 
days  in  the  locality  considered. 

The  temperature  tt  depends  on  the  use  of  the  room.  In 
general  living  rooms,  offices,  schoolrooms  and  other  places 
where  persons  may  be  seated  in  small  numbers  with  wraps 
removed,  the  temperature  is  taken  as  70°  F.,  while  for  halls  a 
lower  temperature  is  used  and  for  churches  where  street  clothes 
are  not  removed  a  temperature  less  than. 70°  is  used.  This 
also  applies  to  places  where  muscular  exercise  takes  place.  The 
following  temperatures,  averaged  from  several  authors,  are 
recommended : 

Warm  air  baths 122°  F. 

Steam  baths 113°  F. 

Massage  rooms 77°  F. 

Hothouses 77°  F. 

Bathrooms 72°  F. 


LOSS  AND  GAIN  OF  HEAT  67 

Hospital  rooms 72°  F. 

Houses,  offices,  schools 70°  F. 

Sewing  rooms 70°  F. 

Laboratories  where  observers  are  seated  and 

physically  at  rest 70°  F. 

Lecture  halls,  auditoriums 66°  F. 

Prisons 65°  F. 

Shops  for  light  work 64°  F. 

Churches 64°  F. 

Sleeping  rooms 60°  F. 

Entrances,  corridors 60°  F. 

Laboratories  with  engines.  . . 55°  F. 

Gymnasiums,  workshops 55°  F. 

When  rooms  are  not  heated  the  radiation  from  other  rooms 
gives  heat  sufficient  to  bring  them  to  a  temperature  above 
the  surrounding  air.  The  following  are  quoted  from  Kinealy 
as  used  by  German  engineers: 

Cellars  and  rooms  kept  closed 32°  F. 

Rooms  often  open  to  outside  as  vestibules.  .  .   23°  F. 

Attics  under  metal  or  slate  roofs 14°  F. 

Attics  under  tile,  cement  or  tar  and  gravel  roofs  23°  F. 

The  temperature  of  garrets  may  be  computed  better  by 
equating  the  heat  loss  through  the  roof  to  the  heat  gain  from 
the  floor  to  the  attic.  This  gives 

.KcAc(ti-ta}=KTAr(ta-t0}.  .        .        .       .        (39) 

The  only  unknown  is  ta,  and  this  may  be  readily  computed. 
The  author  would  recommend  the  following: 

Cellars 36°  F. 

Vestibules 20°  F. 

Attic  under  slate  roof 25°  F. 

Attic  under  book  tile  and  metal  roof 40°  F. 

Attic  under  wood  and  metal  roof 32°F. 


68  ELEMENTS   OF  HEATING  AND  VENTILATION 

The  above  temperatures  of  rooms  for  various  purposes  are 
the  temperatures  found  about  5  ft.  from  the  floor  and  may 
be  used  as  the  average  ti  for  rooms  which  are  not  over  10  ft. 
high.  When  the  room  is  higher  than  this  the  average  tempera- 
ture ti  is  higher  than  the  values  in  the  table.  According  to 
Rietschel  the  values  /  are  those  desired  at  head  height,  and  the 
mean  temperature  t\  must  be  such  that 


—  io)t  .........      (40) 

ti  never  exceeds  i.i5/; 
t  =  desired  temperature  head  high; 
h  —  height  in  room  ; 
/<  =  mean  temperature. 
If  te  =  temperature  at  ceiling, 

io)/  .........     (41) 


Having  found  the  mean  temperatures  of  each  room  or  space 
in  a  building  as  well  as  the  floor  and  ceiling  temperatures  of  high 
rooms,  these  temperatures  should  be  marked  on  the  plans  in  each 
room. 

Effect  of  Exposure  and  Intermittent  Heat.  The  constants 
of  transmission  are  those  found  in  rooms  which  are  not  exposed 
to  violent  winds  and  are  heated  continuously.  When  the  room 
is  exposed  a  percentage  is  added  to  the  quantity  found  and  if 
the  building  is  heated  intermittently  a  similar  method  is  used  so 
that  the  building  may  be  heated  in  a  reasonable  time.  The  fol- 
lowing averages  of  the  allowances  made  by  various  authors  are 
suggested: 

For  north  walls  ............................   add  15  per  cent 

For  east  or  west  walls  ......................  "  10 

For  corner  walls  ..........................  10 

For  rooms  exposed  to  winds  .................  "  15 

For  heating  during  day  and  building  closed  at 

night  .................................  "  10        " 

For  heating  during  day  and  open  at  night  ......  "  30 

For  heating  occurring  at  long  intervals  .........  "  50 


LOSS  AND  GAIN  OF  HEAT  69 

These  allowances  for  occasional  heating  may  be  reduced  if  time 
is  available  for  heating  the  building,  say  10  to  18  hours. 

Heat  Loss  through  Walls.  The  various  factors  K,  A,  and 
(/«  —  to)  now  being  known-,  the  heat  loss  from  the  four  walls,  floor 
and  ceiling  of  any  room  may  be  found  by  the  equation  (27). 

A  very  simple  equation  for  rapid  calculation  is  one  due  to 
Professor  R.  C.  Carpenter  and  is  often  spoken  of  as  Carpenter's 
Rule.  This  is 


(42) 


H  =  B.t.u.'s  to  be  supplied  per  hour; 
G  =  glass  surface  in  sq.ft. 
W  =  net  exposed  wall  area  in  sq.ft.; 
V  =  volume  of  air  supplied  per  hour 

=  nv  where  w  =  'No.  of  times  air  in  room  of  volume  v  cu.it. 
is  changed  per  hour. 

This  gives  a  rapid  method  of  estimating  the  amount  of  heat 
to  be  supplied. 

Heat  for  Ventilation.  If  V  is  the  number  of  cubic  feet  of 
air  per  hour  introduced  into  the  room  from  a  temperature  t0 
and  raised  to  a  temperature  /»  the  amount  of  heat  required  for 
this  will  be 


(43) 


This  becomes  under  general  conditions, 
i4.yXi44X.24 


(44) 


In  this  0.018  is  therefore  the  amount  of  heat  to  raise  i  cu.ft. 
of  air  at  70°  F.,  i°  F.  at  constant  pressure.  This  quantity  for 
rough  calculations  may  be  considered  as  0.02.  The  quantity 


70  ELEMENTS  OF  HEATING  AND  VENTILATION 

Hv  is  the  amount  of  heat  required  to  warm  the  air  to  room  tem- 
perature and  represents  the  amount  of  heat  necessary  to  warm 
the  air  which  may  enter  by  leakage;  or  if  the  air  escapes  at  room 
temperature  it  represents  the  amount  carried  out  by  that  air 
above  the  heat  in  the  air  at  the  temperature  t0. 

It  is  not  necessary  in  finding  the  heat  required  to  warm  the 
ventilating  or  leakage  air,  to  consider  the  air  as  having  a  higher 
temperature  than  ti}  because  the  air  is  supposed  to  leave  at  this 
temperature,  the  higher  temperature  at  which  the  air  entered 
the  room  being  decreased  to  that  of  the  room  by  the  heat  loss 
'from  the  walls,  and  the  amount  for  the  change  of  temperature 
to  that  of  the  room  is  equal  to  the  heat  loss  from  the  walls. 
If  the  amount  of  heat  to  warm  V  cu.it.  of  air  from  fe  to  fa  is 
required,  this  is  approximately  given  by 

Ha  =  O.OlSV(fa-t2') (45) 

If  the  V  is  measured  at  fa  =  120°  F.  instead  of  70°  F.  the  constant 
0.018  would  truly  be  0.0165.  In  using  this  value,  0.018,  it  is 
well  to  remember  that  it  applies  only  when  V  is  the  volume 
considered  at  70°  F. 

Heat  Given  Out  by  Persons,  Lights,  Motors,  etc.  The 
amount  of  heat  given  out  by  persons  working  or  sitting  in  a 
room,  although  not  so  important  when  only  a  few  are  present, 
is  of  genuine  importance  when  a  number  are  to-be  considered. 
The  following  average  values  may  be  used: 

Adult  at  rest 380  B.t.u.  per  hour 

Adult  at  work 470      "          " 

Adult  at  hard  work 550      " 

Adult,  in  old  age 360      "          " 

Infant 63      " 

Child 240      " 

For  electric  lighting: 
hour 


LOSS  AND  GAIN   OF  HEAT  71 

For  gas  lighting: 

i  cu.ft.  natural  gas 1000  B.t.u. 

i  cu.ft.  illuminating  gas 700 

i  cu.ft  producer  gas 150 

i  Welsbach  burner  uses  3  cu.ft.  per  hour, 
i  Fish-tail  burner  uses  5  cu.ft.  per  hour. 

For  motors: 

Motors  used  in  a  room  for  tools  or  apparatus  of  various 
kinds  turn  eventually  all  of  the  power  input  into  heat  which 
remains  in  the  room,  hence, 

i  K.W.  hour  supply  =  3410  B.t.u. 
iH.P.     "         "       =2546     " 

It  is  important  to  realize  that  the  power  developed  to  drive 
all  machines  is  turned  into  heat  provided  that  all  of  the  energy 
is  used  in  a  room.  This  heat  may  be  an  important  item  in  heating 
a  shop  containing  a  large  number  of  tools. 

Equivalent  Temperature.  When  a  given  temperature  T* 
may  be  obtained  in  the  room  of  a  building,  if  the  atmospheric 
temperature  is  Ta,  it  is  often  necessary  to  know  if  this  is  equiv- 
alent to  a  temperature  of  Tg  for  the  rooms  when  the  air 
temperature  is  Tag  these  being  the  guaranteed  conditions.  Now 
for  direct  radiation,  the  loss  equals  the  heat  given  by  the  radia- 
tors. This  means, 


Ts-Tb)    .    (46) 
and  under  guaranteed  conditions, 

(AwKw+A0K0+o.o2V)(Tg-Taff)=KlAr(Ts-Tff)    .  (47) 
Dividing  these  the  following  result: 

'T1    'T*  If       rp  rrt 

26       ±  «        5     -1  »~-^6  /    o\ 

^         ^~  =  ~^~  ^         ^T ....  •  \4°S 

lg  — lag      J^l  1  s  —  J.  g 


72 


ELEMENTS  OF  HEATING  AND  VENTILATION 


Now  KI  is  practically  the  same  as  K,  and  if  it  is  so  considered 
the  following  is  found : 


Ts[Tg+Ta-Tag}-TaT 

1  b  —  rp  rp 

•L  s       J-  ag 

For  an  indirect  system  the  equation  becomes 


.  .  .  .  (49) 


T,-T 


»>j 


•     •  (50) 


In  this  case  Kf  and  K  will  differ  more  than  in  the  previous  case, 
but  if  the  actual  conditions  and  guaranteed  conditions  are  not 
far  different  these  two  quantities  may  be  considered  equal,  and 
the  expression  for  Tb  is  the  same  as  given  above. 

This  is  given  in  a  table  below  for  zero  outside  weather  in  the 
guarantee  and  steam  at  5  Ibs.  gage  pressure. 

EQUIVALENT  INSIDE  TEMPERATURE 


Actual 


Guaranteed  inside  Temperature. 


Outside  Temperature. 

50 

60 

70 

80 

—  10 

42.2 

52-6 

63-1 

73-5 

O 

5O.O 

60.0 

70.0 

80.0 

10 

57-8 

67.4 

76.9 

86.5 

20 

65.6 

74-8 

83-8 

93-0 

30 

73-4 

82.2 

90.7 

99-5 

CHAPTER  IV 

RADIATORS,  VALVES  AND  HEAT  TRANSMISSION  FROM  RADIATORS 

Radiators  are  of  various  forms.     Some  are  made  of   cast 
iron  or  pressed  steel  and  some  are  made  of  wrought-iron  pipe. 


FIG.  41. — Peerless  Three-column  Radiator. 

The  common  form  of  cast-iron  radiator,  Fig.  41,  is  made  by  con- 
necting several  cast-iron  sections  together  by  close  threaded 
right  and  left  nipples  as  shown  in  Fig.  42,  or  by  using  conical 

73 


74 


ELEMENTS   OF  HEATING  AND  VENTILATION 


ended  thimbles  which  are  held  in  place  in  the  sections  by  means 
of  the  bolts.  The  nipples  are  made  with  a  projection  on  the 
inside  so  that  they  may  be  turned  by  a  bar  which  forms  a  plug 
wrench.  The  sections  are  made  of  various  heights  from  13 
to  45  ins.,  and  in  order  to  give  varying  amounts  of  heating 


FIG.  42. — Section  of  Loops  Showing  Nipple. 

surface  they  are  made  of  various  widths.  The  widths  are 
changed  by  increasing  the  number  of  tubes  forming  single 
column,  two  column,  three  column,  or  four  column  radiators.  The 
design  of  the  exterior  of  these  radiators  is  varied  to  suit  different 
architectural  requirements.  Figs.  41,  43,  44  and  45  illus- 
trate different  styles  of  various  typical  radiators  made  by  the 
American  Radiator  Company. 


RADIATORS,  VALVES  AND  HEAT  TRANSMISSION    75 


These  radiators  are  connected  at  the  lower  end  of  each 
section  for  steam  work,  while  for  hot-water  systems  the  sections 
are  connected  at  the  top  and  bottom  as  shown  in  Fig.  46.  The 
purpose  of  this  is  to  aid  in  the  circulation  of  the  water  by  bring- 
ing it  in  at  the  top  and  distributing  it  to  the  various  sections 


FIG.  43. — Peerless  Single  Column 
Radiator. 


FIG.  44. — Rococo  Two-column 
Radiator. 


which  act  as  down-takes.  This  figure  illustrates  the  method 
of  constructing  these  radiators  when  it  is  desired  to  have  the 
floor  line  clear.  The  leg  sections  are  not  used  in  forming  the 
radiator  and  the  radiator  is  held  by  a  bottom  support  and  top 
guide,  Fig.  47. 

At  times  the  sections  are  so  constructed  that  they  form, 
by  projecting  fins  or  webs,  a  series  of  closed  passages  between 


76 


ELEMENTS  OF  HEATING  AND  VENTILATION 


sections.     Such  radiators,   Fig.  48,  are  known  as  flue  or  box 
radiators.     This  form  is  used  in  the  direct-indirect  system  of  heat- 


\ 


FIG.  45. — Rococo  Four-column 
Radiator. 


FIG.  46. — Hot  Water  Radiator  on 
Brackets. 


0 

i 

TOP  GUIDE' 

^  .BIOTTQM  SUPPORT 
FIG.  47. — Brackets  for  Wall  Radiators. 

ing,  shown  in  Fig.  6,  in  which  it  is  desired  to  draw  in  a  certain 
amount  of  air  for  ventilation. 


FIG.  48.— Flue  Box  Base  Radiator. 


FIG.  49. — Stairway  Radiator. 


77 


V 


FIG.  50. — Corner  Radiator. 
22 

>*N 

0 


FIG.  51. — Circular  Radiators. 


78 


RADIATORS,  VALVES  AND  HEAT  TRANSMISSION         79 


__.=:-^. 

D 

n 

r 

= 

^ 

PI 

-N 

^7/ 

V 

1  - 

\ 

]•••• 

r  I 

u 

" 

" 

- 

' 

STYLE  B 


FIG.  52. — Rococo  Wall  Radiators. 


FIG.  53.— Dining  Room  Radiator. 


80 


ELEMENTS   OF  HEATING  AND  VENTILATION 


The  heights  of  the  radiators  are  selected  to  fit  the  particular 
positions  in  which  they  are  to  be  placed.  Usually  it  is  well  to 
have  them  lower  than  a  window  sill  in  front  of  which  they  are 
to  stand.  At  times  they  are  put  beside  the  jib  panel  of  a  stair- 
way, and  in  such  a  case  a  number  of  different  sizes  may  be 
united  to  suit  the  steps.  Fig.  49  is  one  of  this  form.  Low 


-Uu 


FIG.  54. — Plate  Warmer  or  Pantry 
Radiator. 


FIG.  55.— Detachable  High 
Leg  Section. 


radiators  are  made  of  such  dimensions  that  they  may  be  placed 
under  window  seats,  and  in  these  cases  they  are  known  as  window 
radiators. 

When  a  corner  radiator  is  to  be  placed  in  a  room,  Fig.  50, 
or  is  to  be  made  circular  to  fit  around  a  column,  Fig.  51,  special 
sections  are  made  and  joined  together  to  form  these.  These 
may  be  placed  where  they  are  needed  for  architectural  effects; 


RADIATORS,  VALVES  AND  HEAT  TRANSMISSION         81 

they  are  not  often  used.     In  most  cases  the  circular  radiator 
is  made  in  halves. 

The  radiator  shown  in  Fig.  52  is  known  as  the  Rococo  wall 
radiator,  and  this  type  is  employed  when  little  space  is  available. 
The  sections  are  made  so  that  they  may  be  joined  at  the  various 
corners  and  by  making  various  combinations  of  elements,  dif- 


I 

^fi 

crS 

i^ 

i 

^ 

JL 

~^J. 
J- 

^-£ 

J- 

•^_£ 

J- 

^ 

J- 

-£ 
J- 

^ 

4 

~~£: 

4 

J- 

n 

\ 

X 

•\ 

I 

FIG.  56.  —  Radiator  Foot  Ups. 


ferent  shaped  spaces  may  be  filled.     These  radiators  are  made 
of  the  following  dimensions: 


Section  No. 

5^4 

7 A  and  -jB 

gA  and  gB 


Length. 
i6f  ins. 

21*     " 


Width, 
ins. 


I3&   " 


Thickness. 
2 1  ins. 


Area. 
5  sq.ft. 

7      " 
9      " 


These  are  the  over  all  dimensions  of  the  section,  and  various 
sections  may  be  so  connected  by  nipples  that  they  come  together, 
iron  to  iron. 

Radiators  may  be  joined  together  forming  a  sort  of  cup- 
board, giving  a  so-called  dining-room  or  pantry  radiator,  Fig. 
53.  Plate  warmers,  Fig.  54,  may  be  constructed  by  using  wall 
radiators. 

The  leg  loops  of  radiators  are  sometimes  made  with  a 
detachable  leg,  Fig.  55,  so  that  in  moving  carpets  the  leg  at 


82  ELEMENTS  OF  HEATING  AND  VENTILATION 

one  end  may  be  removed  and  then  at  the  other.     The  radiator 


FIG.  57. — Pedestals. 


foot  ups,  Fig.  56,  may  be  used  for  the  same  purposes.     Radiator 

pedestals,  Fig.  57,  may  be  used 
to  raise  the  radiator  from  the 
floor  an  additional  distance  when 
necessary. 

Fig.  58  gives  the  appearance 
of  the  Kinnear  pressed  steel 
radiator.  The  radiators  are  light 
and  will  not  crack.  They  are 
giving  good  satisfaction.  The 
following  tables  give  data  in 
regard  to  the  size  of  the  vari- 
ous radiators,  where  F\  refers 
to  height  to  center  of  steam 
supply,  or  supply  and  return 
tapping  for  water,  while  F%  re- 

\  N^/      \L)^^  ^ers   to   tapping   for   single   pipe 

^•*s> i  f  steam    or    return    in    two    pipe 

Q  steam. 

Pipe  coil  radiators  or  pipe  coils 

are  very  satisfactory.    They  are  made  by  joining  pipes  together 


RADIATORS,   VALVES  AND   HEAT  TRANSMISSION 


83 


MEASUREMENTS  OF  AMERICAN  RADIATORS 


Pattern. 

A 

B 

c 

D 

E 

ft 

n 

Heating 
surface 
sq.ft. 

Rococo,  Peerless  one  column  . 

38 

3iA 

44 

5J 

24 

44 

4 

3 

32 

254* 

44 

24 

44 

4 

26 

194* 

•  44 

5§ 

24 

44 

4 

2 

23 

16^ 

45 

52- 

24 

4 

If 

2O 

i3ti 

44 

s4 

24 

44 

4 

Two-column(Peerless  Hospital 

45 

387 

7l 

84 

24 

44 

4 

5 

radiators  same  as  this,  ex- 

38 

7f 

8^ 

44 

4 

4 

cept  £  is  3  ins.  in  place  of 

32 

25ei 

7f 

84 

24 

44 

4 

34 

24) 

26 

194* 

7l 

84 

24 

44 

4 

2| 

23 

16^ 

7f 

84 

24 

44 

4 

2^ 

20 

13^4 

7l 

84 

24 

44 

4 

2 

Peerless  only 

I  e 

7i 

o  I 

2i 

I 

Ii 

Three  column 

-1  o 

815 

/  8 

en    O 

IO 

-  2 

I 

2 

5 

38 

3iA 

en    cj 

10 

24 

44 

4 

5 

32 

25^ 

CU     O 

<U  p^ 

10 

24 

44 

4 

44 

26 

i94* 

.    en 

10 

24 

44 

4 

3f 

22 

15^2 

.S  '" 

10 

24 

44 

4 

3 

18 

IXA 

O'c* 

10 

2* 

44 

4 

2! 

Four  column  

45 

38  n 

io| 

"I 

3 

44 

44 

10 

38 

31-3% 

io| 

iii 

3 

44 

44 

8 

*• 

32 

25M 

104 

nl 

3 

44 

44 

54 

26 

194* 

io| 

n| 

3 

44 

44 

5 

22 

153*2 

ro4 

iii- 

3 

44 

44 

4 

18 

"A 

iil 

3 

44 

44 

3 

Rococo  window  

20 

IC.  1 

i2i 

I2i 

2 

a 

2 

16 

nA 

j.  ^  2 

124 

•J 

3 

o 
3 

o 
3 

3! 

13 

STS 

I2| 

124 

3 

3 

3 

3 

Italian  flue  

38 

3J    5 

gi 

gi 

1 

7 

32 

25l£ 

U2 

"2 

3 

4! 

4 

/ 

sf 

26 

194 

85 

s| 

3 

44 

4 

44 

20 

I3A 

8^ 

84 

3 

44 

4, 

3! 

Italian  flue  Dir.-ind  

3Q- 

~j_5_ 

8- 

84 

, 

6 

_i 

_ 

33l 

25^ 

g| 

*-'2 

3 

6 

54 

s! 

274 

194 

85 

84 

3 

6 

54 

44 

2*4 

IS* 

84 

84 

3 

6 

54 

3! 

84 


ELEMENTS  OF  HEATING  AND  VENTILATION 


by  return  bends,  Fig.  59,  or  by  branch  tees  or  manifolds,  Fig.  60. 
In  all  cases,  it  must  be  remembered  that  some  of  the  pipes  are 


D 


FIG.  59. — Pipe  Coil  with  Return  Bends. 


FIG.  60.— Pipe  Coil  with  Manifolds. 


FIG.  61. — Improper  Form  of  Pipe  Coil. 

apt  to  heat  first,  so  that  such  a  construction  as  shown  in  Fig. 
6 1  is  improper,  as  the  expansion  of  the  top  pipe  before  the  other 
pipes  are  heated  is  apt  to  cause  the  rupture  of  the  branch  tees 


RADIATORS,  VALVES  AND  HEAT  TRANSMISSION    85 

The  arrangement  shown  in  Figs.  59  and  60  permits  the  expan- 
sion of  any  individual  pipe  without  straining  the  system.  In 
all  coil  construction  one  must  remember  that  any  one  pipe 


£ 


FIG.  62. — Coil  with  Bends  and  Manifold. 

may  expand  more  than  any  other.  Fig.  62  is  a  fairly  good  con- 
struction, although  here  there  may  be  unequal  expansion  of  one 
pipe  of  any  set  which  will  bring  a  strain  on  the  return  bend. 


FIG.  63.— Corner  Coil. 

The  fact  that  air  may  collect  in  any  set  is  another  objection 
to  this  system.  Fig.  63  is  a  coil  of  good  construction  to  be 
used  at  the  corner  of  a  room.  In  this  form  expansion  may 
occur  in  any  pipe. 


86 


ELEMENTS   OF  HEATING  AND  VENTILATION 


For  the  purpose  of  giving  data  to  be  used  for  coil  construc- 
tion, the  following  table  of  certain  sizes  is  added. 

DATA  FROM  WROUGHT  IRON  PIPE 


i 

L! 

£jj 

! 

Q 

Internal 

External 

CO  0- 

0  §* 

ja 

"c-^ 

o 

rt 

i 

Area. 

Area. 

*J 

rt  j-" 

- 

v  ti 

c 

2 

^ 

-o 

!«. 

* 

c  s 

^ 

^ 

1 

'55 
^C 

|a 

M  £P 

M    C 

<u 

1 

t-C 

0, 

«« 

6 

s 

•a 

3 

2* 

CTj  "^ 

jp 

P 

bo 

]d 

03 

1 

J3 

•n 
£ 

£ 

* 

1 

sq.in. 

sq.ft. 

sq.in. 

sq.ft. 

X**"1 

1 

3 

o 

p 

1 

"w 

i|  0.36 

0.54 

o.  104 

0.0007 

0.229 

0.0016 

0.095 

0.14 

0.42 

18 

0.29 

0.05: 

4!  0.62 

0.84 

0.304 

0.0021 

0.554 

0.0038 

0.  163 

0.22 

0.84 

14 

0.39 

O.O8: 

il  0.82 

i.  05 

0.533 

0.0037 

o  .  866  o  .  0060 

o.  216 

0.28 

I  .  12 

14 

.40 

O.  II  i 

i   1   i.  05 

1.32 

0.861 

o  .  0060 

1.358 

0.0094 

0.274 

0.34 

1.6?  0.006 

•  51 

o.  i6i 

|! 

1.38 
1.61 
2.07 

1.66 
1.90 
2.38 

i  .50 
2.036 
3.356 

0.0104 
0.0141 
0.0233 

2.  164  0.0150 
2.835  0.0197 
4.430)0.0308 

0.361 
0  .  443 
0.541 

0.43 

0.50 
0.62 

2.  24  O.OIO 

2.68  0.014 
3.61  0.023 

11} 

•54 
•  55 
-58 

0.22^ 

0.27 

0.36 

25 

2-47 

2.87 

4-78 

0.0332 

6.492  0.0451 

0.646 

0.75 

5.74  0.03 

8 

.89 

0-575 

3 

3-07 

3-SO 

7-38 

0.0513 

9.621 

o  .  0668 

0.744'o.92J   7-540.05 

8 

•  95 

0.751 

4 

4-03 

4-50 

12.73 

0.0884 

15.904 

o.  1104 

1.05 

I.I8JI0.66  0.09 

8 

1  .08 

5 

5-05 

5-56 

19.98 

o.  1388 

24.301 

0.1688 

1.32 

1.45  14-500.14 

8 

'    16 

1.45 

6 

6.06 

6.63 

28.89 

o.  2006 

34-47 

0.2394 

1-59 

1.73  18.76  0.2 

8 

1.26 

r.88 

8 

7.98 

8.62 

50.03 

0.3474 

58.43 

0.4057 

2.09 

2.  25  28.  18  0.34 

8 

1.46 

2.82 

10 

10.02 

10.75 

78.83 

0-5474 

90.76 

0.6303 

2.62 

2.  8  1  40.06  o.  54 

8 

1.68 

3.20 

12 

12.00 

12.75 

113.  10 

0.7854 

127.68    0.8867 

3.14 

3-33 

49.00 

0.78 

8 

1.88 

4  SO 

For  indirect  heating  the  radiators  are  so  arranged  that  the 
air  passing  the  surface  may  abstract  heat  readily.  The  coil 
form  of  radiator  or  heater  is  arranged  usually  with  four  staggered 
rows  of  i -in.  pipe.  The  pipes,  Fig.  64,  are  attached  at  two 
places  to  a  cast-iron  base.  In  some  forms,  as  those  of  the  B.  F. 
Sturtevant  Co.  and  the  Buffalo  Forge  Co.,  the  division  between 
the  supply  and  return  is  made  at  the  center  of  the  base,  while 
the  Massachusetts  Fan  Company  divides  its  base  by  a  longi- 
tudinal partition. 

The  pipes  of  Fig.  64  are  constructed  with  one  piece  of  each 
section  with  right  and  left  ends.  The  steam  is  supplied  through 
the  upper  section  of  the  base  and  is  discharged  into  the  lower 
section.  The  small  hole  relieves  the  upper  part  of  water.  The 
figure  shows  the  forms  .of  base  used  by  the  two  companies. 

The  type  shown  in  Fig.  65  is  that  used  generally  by  the 
Massachusetts  Fan  Company,  although  it  is  also  used  by  others. 
The  base  is  divided  by  a  vertical  partition  with  a  drain  hole 


0 


STURTEVANT  BASE 

FIG.  64.— Coil  Heater  Section. 

OQOQQQQQ 


FIG.  65. — Massachusetts  Coil. 


87 


88 


ELEMENTS   OF  HEATING  AND  VENTILATION 


at  one  point.     The  sections  are  of  varying  length  for  simplicity 
in  construction. 

Fig.  66  gives  the  form  of  the  "positivflo"  heater  of  the  Green 
Fuel  Economizer  Co.     In  this  heater  the  horizontal  tubes  are 


o 


'  LS-3* 


O    O    <V/D    0000000000000 

O    0/0   00000000000000 
O    O//O    OOOOOOQOOOOOOO     i 


attached  at  each  end  to  a  header  box,  the  front  one  of  which 
is  separated  into  two  parts  by  a  partition,  so  that  the  steam 
flows  in  one  direction  through  one  half  of  the  tubes,  returning 
to  the  front  by  the  other  half. 

Cast  forms  of  indirect  radiators  have  been  used  for  many 


RADIATORS,  VALVES  AND  HEAT  TRANSMISSION        89 


years;  the  advantage  claimed  for  them  is  a  small  number  of 
joints  and,  if  properly  designed,  a  more  compact  radiator.  A 
recent  form  introduced  by  the  American  Radiator  Company 
is  the  Vento  Cast  Iron  Hot  Blast  Heater,  Fig.  67.  In  the  figure 

a  section  through  the  pro- 
jections of  the  heater  is 
shown  from  which  it  is  seen 
that  there  is  ample  space 
for  steam  or  water  to  reach 
all  parts  of  the  section. 
Occasional  ties  are  cast  in 
the  interior  to  support  the 
flat  plate.  These  sections 
are  united  by  right  and 
left  hexagonal  nipples  which 


FIG.  67.— Vento  Heater. 


FIG.  68. — Right  and  Left  Nipples. 


are  screwed  in  when  the  heaters  are  made  up  into  stacks. 
The  number  of  sections  in  a  stack  varies  with  the  require- 
ments of  an  installation.  Twenty-four  is  the  largest  number 
that  is  recommended  to  be  put  together,  and  when  supply  and 
return  are  to  be  placed  at  the  same  end  of  a  stack  eighteen 
sections  is  the  limit. 

These  are  made  of  two  forms,  regular  and  narrow,  in  three 
lengths,  40  ins.,  containing  10.75  sq.ft.  (reg.)  or  7.5  sq.ft.  (narrow), 


90 


ELEMENTS  OF  HEATING  AND  VENTILATION 


50  ins.  containing  13.5  sq.ft.  (reg.)  or  9.5  sq.ft.  (narrow),  and 
60  ins.  containing  16  sq.ft.  (reg.)  or  n  sq.ft.  (narrow). 

The  nipples  are  made  of  such  length  that  the  sections  may  be 
placed  4!,  5  or  5!  ins.  on  centers.  These  give  the  following 
areas  between  sections  for  the  passage  of  air. 

NET  AIR   SPACE   IN   SQUARE    FEET 


Sections 

Centers 

4f  in. 

5  in. 

5|  in. 

40 
50 
60 

0.52 
0.65 
0.78 

O.62 
0.77 
0.92 

0.72 
O.QI 
1.  08 

The  widths  of  the  regular  sections  are  gj  ins.  while  the  narrow 
sections  are  6f  ins. 

Fig.  69  gives  the  dimensions  of  the  vento  sections.     Fig. 


— 60$'  For  60  Section 
—41  £t"For  40Section 


)§  For  50  Section- 


FIG.  69. — Measurements  of  Regular  Vento  Heaters. 

70  illustrates  an  Excelsior  Indirect  Radiator  built  by  the  Ameri- 
can Radiator  Co.  The  detail  of  the  end  shows  how  the  flow 
is  directed  through  the  upper  pipe  and  down  to  the  bottom  pipe 
to  the  next  radiator.  The  fins  on  the  outside  increase  the  heat- 
ing surface.  These  radiators  are  usually  employed  where 
individual  heat  stacks  are  placed  beneath  a  room  or  set  of  rooms 
to  be  heated. 

The  sections  are  23!  ins.  or  36  by  8  ins.  and  the  thickness 
or  width  is  3!  ins.     These  contain  8  or  12  sq.ft.  of  radiating 


RADIATORS,  VALVES  AND  HEAT  TRANSMISSION        91 


V 


J 


\ 


\ 


FIG.  70. — Excelsior  Indirect  Radiator. 


FIG,  71. — Sterling  Indirect  Radiator. 


92  ELEMENTS  OF  HEATING  AND  VENTILATION 

surface.  Fig.  71  represents  their  Sterling  Indirect  Radiator, 
which  is  somewhat  similar  in  form.  Each  section  contains 
20  sq.ft.  of  surface  and  requires  a  space  of  36!  by  15!  by  3!  ins. 
The  Perfection  Pin  Indirect  Radiator,  Fig.  72,  may  be  used 
for  the  same  purpose.  The  American  Radiator  Company 
build  these  in  different  forms,  containing  10  sq.ft.  and  15  sq.ft. 
of  heating  surface.  The  length  is  36 J  ins.  and  the  height  is 
7!  or  ii J  ins.  on  the  square  part,  while  the  projecting  points 
increase  the  height  i\  ins.  The  width  of  the  sections  is  about 
2!  ins.  The  tappings  for  this  radiator  are  made  at  different 
points  on  the  projecting  ends  to  suit  given  conditions. 


FIG.  72. — Perfection  Pin  Radiator. 

All  of  the  last  forms  are  intended  for  small  individual  stacks 
with  natural  circulation. 

The  coil  radiators  are  sometimes  formed  as  miter  coils, 
Fig.  73,  in  which  steam  is  admitted  at  the  upper  end  and  the  con- 
densed steam  is  discharged  at  the  lower  end.  The  arrangement 
permits  expansion  to  occur. 

Valves.  The  valves  used  on  radiators  are  usually  of  the  angle 
form  and  made  with  a  union  on  one  side,  although  any  form 
of  valve  could  be  used.  The  reason  for  this  peculiar  form  is 
that  it  is  desirable  to  have  close  connections  from  the  radiator, 
as  it  is  objectionable  to  have  the  pipes  extend  far  beyond  the 
radiator,  obstructing  space  and  forming  a  barrier  over  which 
persons  might  trip. 

The  Norwall  Packless  Radiator  valve,  Fig.  74,  illustrates 
the  form  of  angle  valve  with  the  union  on  the  left-hand  side. 


RADIATORS,  VALVES  AND  HEAT  TRANSMISSION       93 

In  the  valve  shown  the  valve  disc  has  a  piston  A  which 
prevents  steam  from  coming  in  contact  with  the  spindle.  In 
addition  there  is  a  packing  around  the  spindle  at  C  held  tight 


FIG.  73.— Miter  Coil. 

by  the  spring  D.  The  spring  disc  at  B  is  intended  to  make  up 
for  the  contraction  of  the  spindle  as  the  valve  cools  off,  thus 
keeping  the  disc  against  its  seat.  The  arrangement  of  threads, 
makes  this  a  quick  opening  valve. 


94 


ELEMENTS   OF  HEATING  AND  VENTILATION 


The  ordinary  form  of  radiator  valve  as  made  by  Jenkins 
Bros,  or  Crane  is  similar  to  this,  with  the  exception  that  the 
spindle  is  attached  by  a  shoulder  to  the  disc.  The  spindle 
thread  works  in  the  bonnet  of  the  valve  and  the  stem  is  packed 
by  a  stuffing  box. 

The  American  Radiator  Company  has  adapted  their  cor- 


FIG.  74. — Norwall  Packless  Valve. 

rugated  metallic  bellows  or  Sylphon  to  the  construction  of  the 
Sylphon  Packless  Radiator  Valve,  Fig.  75.  In  this  valve  the 
bellows  A  is  attached  to  a  cup  B  on  the  valve  disc  and  to  the 
bonnet  at  the  top.  This  encloses  the  spindle  in  a  space  which 
is  free  from  steam.  The  extension  or  contraction  of  the  bellows 
occurs  as  the  valve  is  moved  in  or  out.  The  sylphon  is  made 
of  steam  brass  and  will  stand  repeated  extensions  without 
rupture. 


RADIATORS,   VALVES  AND   HEAT  TRANSMISSION        95 

The  Q.  O.  Water  Radiator  Valve  (quick  opening)  is  shown  in 
Fig.  76.  Most  water  radiator  valves  are  made  in  the  form  of 
cocks,  so  that  a  quarter  turn  will  open  them.  The  valve  shown 
is  so  made  that  the  conical  body  comes  in  contact  with  the 
body  of  the  valve  at  top,  bottom  and  small  vertical  strips  on 
each  side,  which  form  a  partition  between  the  outlet  and  inlet 


FIG.  75. — Sylphon  Packless 
Valve. 


FIG.  76.— Q.  O.  Water 
Radiator  Valve. 


sides  of  the  valve.  The  taper  permits  of  taking  up  wear,  the 
spring  at  the  top  pressing  the  valve  against  its  seat.  This 
spring  presses  against  the  washer  around  the  spindle  of  the 
valve. 

In  some  cases  a  small  hole  is  made  in  the  valve  allowing 
sufficient  circulation  in  radiators  which  are  shut  off,  to  prevent 
freezing  in  cold  weather. 


96 


ELEMENTS  OF  HEATING  AND  VENTILATION 


A  corner  valve,  Fig.  77,  of  either  right  or  left-hand  con- 
struction is  necessary  at  times  on  account  of  the  position  of  the 
piping.  This  does  away  with  elbows  and  shortens  up  connec- 
tions. 

When  it  is  necessary  to  turn  steam  or  water  on  a  radiator 
and  have  the  same  beyond  the  control  of  the  occupants  of  the 
room,  a  lock  and  shield  radiator  valve,  Fig.  78,  is  used. 
The  spindle  of  the  valve  is  surrounded  by  a  shield,  and  a  key 


1 L 


FIG.  77. — Corner  Valve. 


FIG.  78.— Lock  and  Shield  Valve. 


or  extension  handle  fitting  over  the  spindle  is  used  to  operate 
the  valve. 

Special  valves  are  used  on  radiators  to  cut  down  excessive 
use  of  steam  and  to  reduce  the  pressure  in  the  return  pipes. 
Figs.  79  and  80  illustrate  the  Thermograde  System  of  valves  for 
this  purpose.  There  are  two  valves  used,  the  modulation  or 
control  valve  A  and  the  auto- valve  B.  The  control  valve  A  has  a 
handle  C  with  a  pointer  moving  over  a  graduated  scale,  and 
on  the  handle  is  an  adjustable  pin  Z>,  moving  over  a  cam  E,  so 
that  when  the  pointer  is  at  J  the  valve  F  is  raised  from  its 
seat  an  amount  which  will  just  admit  enough  steam  to  heat 
J-  of  the  radiator.  When  the  handle  is  moved  to  "  full  "  the  rapid 


RADIATORS,  VALVES  AND  HEAT  TRANSMISSION        97 
rise  in  the  cam  opens  the  valve  a  large  amount.     The  pin  G 


is  used  to  adjust  the  cam  which  is  attached  on  one  part  of  its 
circumference,  the  remaining  part  being  split. 


98 


ELEMENTS  OF  HEATING  AND  VENTILATION 


The  auto-valve  is  in  reality  a  trap  which  will  not  allow 
steam  to  pass.  It  consists  of  a  brass  vessel  H  with  a  copper 
bottom  which  contains  a  liquid  hydrocarbon  such  as  gasoline. 
When  this  is  cold  the  spring  pressure  lifts  the  valve,  pressing 
in  the  copper  bottom,  which  may  be  corrugated.  The  screw 

/  adjusts  the  position  of  this 
so  that  /  is  lifted  from 
its  seat  when  this  condition 
occurs,  but  when  steam 
reaches  the  discharge,  the 
heat  volatilizes  part  of  the 
liquid  in  H  and  produces 
sufficient  pressure  to  push 
the  valve  stem  down  against 
the  spring  pressure  closing 
off  the  valve.  /  may  be 
adjusted  so  that  this  occurs 
at  some  definite  tempera- 
ture. 

The  two  valves  are  shown 
in  their  position  on  a  radiator 
in  Fig.  80.  In  this  installa- 
tion hot-water  radiators  are  used,  as  it  is  desired  to  have  the 
steam  supply  the  tops  of  all, coils  and  blow  out  the  air  contained. 
There  is  no  necessity  for  air  valves  in  such  a  system  as  this, 
and  with  proper  adjustment  of  the  modulation  valve  the  admis- 
sion of  steam  will  heat  about  the  amount  of  surface  marked 
on  the  dial. 

Fig.  8 1  illustrates  the  method  used  by  Warren  Webster  &  Co. 
to  accomplish  the  same  result. 

The  modulation  valve  A  consists  of  a  valve  casing  in  which 
a  disc  D  having  four  holes  in  it  passes  beneath  a  diaphragm  E 
having  one  hole.  The  disc  is  moved  by  the  handle  F  on 
the  spindle.  When  the  pointer  on  the  handle  is  over  the  mark 
"i"  on  the  dial  a  small  hole  in  the  disc  registers  with  the  hole  in 
the  diaphragm  This  admits  enough  heat  to  warm  part  of  the 
radiator  surface.  When  the  handle  is  placed  at  the  other 


u 


FIG.  80. — Thermograde  Valves. 


RADIATORS,  VALVES  AND  HEAT  TRANSMISSION        99 

marks,  "  2,"  "  3  "  or    "  open,"  holes  of  the  correct  size  come 
into  the  proper  positions  to  admit  more  steam. 

The  motor  discharge  valve  is  placed  on  the  return  end  of  the 


CO         > 


radiator.  Water  collecting  will  cause  the  ball  float  G  to  rise. 
This  float  acts  as  a  valve  and  the  water  escapes  over  the  com- 
position seat  H.  When  the  ball  is  seated  air  may  be  drawn 
from  the  radiator  through  the  space  between  the  tube  in  the  ball 


100 


ELEMENTS  OF  HEATING  AND  VENTILATION 


G  and  the  threaded  rod.  As  soon  as  steam  begins  to  go  over, 
this  condenses  in  the  threads  and  the  passage  of  this  condensate 
over  the  threads  is  very  slow. 

The  Monash  valve  to  be  placed  on  the  drip  of  the  radiator 
is  somewhat  similar  in  action  to  the  above  valve. 

As  shown  in  Fig.  82  there  is  a  water  seal  in  this  valve,  and 
yet  the  air  can  be  drawn  around  the  center  spindle  by  the 


FIG.  82. — Monash  Radifier. 

vacuum  pump.  There  are  by-passes  to  drain  and  clean  the  vaive. 
This  valve  is  called  a  radifier.  The  advantage  of  these  three 
return  valves  is  that  there  is  no  pressure  in  the  return  pipe. 

The  fact  that  air  may  collect  in  most  radiators,  preventing 
the  proper  heating  of  the  radiator  and  producing  noise,  makes 
it  necessary  to  use  air  valves  on  many  forms  of  radiators.  These 
may  be  automatic  or  hand  controlled.  In  most  cases  there  is 
considerable  trouble  with  the  automatic  form,  as  they  are  liable 
to  get  out  of  adjustment.  Fig.  83  illustrates  two  forms  of 


itADIATORS,   VALVES  AND  HEAT  TRANSMISSION      101 


compression  air  valves,  one  operated  by  a  removable  key,  the 

other  by  a  handle.     These  are  nothing  but  small  conical  valves. 

In  Fig.  84,  an  expansion  form  of  automatic  air  valve  is  shown. 


FIG.  83. — Compression  Air  Valves. 

In  this  valve  the  core  or  cylinder  has  a  coefficient  of  expansion  so 
different  from  that  of  the  body  of  the  valve  that  when  adjusted 
by  the  slot  in  its  end  so  that  air  will  just  discharge  when  cold, 


FIG.  84. — Expansion  Air  Valve. 

the  valve  will  be  shut  off  as  soon  as  hot  water  or  steam  strikes 
the  valve.     This  form  has  been  used  for  a  considerable  time. 

The  Allen  Automatic  Air  Valve,  Fig.  85,  is  formed  of  two 
chambers,  C   and   B,   connected  by  a  hole  A  at  the   bottom. 


102 


ELEMENTS  OF  HEATING  AND  VENTILATION 


The  cylinder  D  is  closed.  When  there  is  no  water  in  C  the 
cylinder  D  rests  on  the  bottom  of  C  and  the  pin  at  its  upper  end 
does  not  fill  the  hole.  Air  will  then  escape  from  the  radiator 
which  is  connected  at  E.  When  steam  reaches  the  valve,  the 
condensation  of  it  fills  the  bottom  and  floats  the  cylinder  D, 


Allen  Air  Valve.  Libra  Automatic  Air  Valve. 

FIG.  85. — Air  Valves. 

closing  the  hole.  After  this  cools  off  the  contraction  of  the  air 
in  B  draws  some  of  the  water  from  C  and  allows  D  to  fall,  thus 
opening  the  air  vent.  The  valve  is  kept  hot  by  conduction 
from  the  radiator  as  long  as  the  steam  is  turned  on. 

The  valve  shown  in  Fig.  85  is  the  Libra  Automatic  Air  Valve. 
The  inner  cylinder  is  open  at  the  bottom  and  when  steam  enters 
the  valve,  the  air  contained  within  the  cylinder,  expanding 


RADIATORS,   VALVES  AND   HEAT  TRANSMISSION      103 


from  the  heat,  forces  the  water  out  and  floats  the  cylinder, 
closing  the  valve.  This  water  collects  when  the  valve  is  first 
attached  to  the  radiator. 

The  above  valves  permit  air  to  enter  the  radiator  after  steam 
is  shut  off.  This  of  course  means  that  when  the  radiator  is 
opened  again,  a  certain  time  must  elapse  before  the  air  is  all 
removed  and  the  radiator  is  completely  heated.  To  prevent 
this  action  the  Norwall  Automatic  Syphon  Air  and  Vacuum  Valve 
is  used.  This  valve  is  similar 
to  those  described  above  with 
the  addition  of  a  syphon  A  and 
the  vacuum  head  B.  The  syphon 
A  extends  into  the  radiator  and 
fills  the  lower  part  of  the  valve 
with  water,  if  the  radiator  has 
liquid  in  it,  before  this  reaches 
the  level  of  the  outlet.  This 
water  lifts  the  float  and  closes 
off  the  discharge  until  the  water 
is  drawn  from  the  radiator. 
The  vacuum  head  B  contains  a 
diaphragm  of  bronze  containing 
a  port  which  may  be  closed  by 
a  ball  on  the  end  of  a  small  rod. 
The  rod  is  supported  by  a  yoke 
and  two  adjusting  nuts.  The 
length  of  the  rod  is  such  that 
when  the  pressure  below  the  dia- 
phragm is  slightly  above  atmospheric  pressure  the  disc  is 
raised,  allowing  air  or  vapor  to  pass  out  through  holes  in  the  head. 
As  soon  as  the  pressure  is  atmospheric  the  diaphragm  rests  on 
the  ball,  closing  off  the  opening  around  the  rod.  The  greater 
the  vacuum  below  the  diaphragm,  the  tighter  the  opening  is 
closed. 

The  sylphon  bellows  is  applied  to  an  air  valve  in  Fig.  87^4. 
The  bellows  has  a  volatile  liquid  within  it  which  vaporizes  when 
subject  to  heat  from  steam  and  closes  the  air  valve.  The  float 


FIG.  86. — Combined  Air  and  Vacuum 
Valve.  ' 


104 


ELEMENTS   OF  HEATING  AND  VENTILATION 


above  is  intended  to  close  the  vent  if  the  radiator  is  flooded  with 
water.     The  vent  pin  is  self-guiding. 

The  Sylphon  Vacuum  and  Air  Valve.  Fig.  87  J3  has  the  closed 
bellows  with  the  volatile  liquid  at  the  bottom  and  a  float  Z>, 
while  above  this,  carrying  the  valve  seat,  is  an  empty  bellows 
so  made  that  the  valve  seat  rests  against  the  valve.  When 
pressure  from  the  radiator  is  slightly  in  excess  of  the  atmos- 
phere, the  bellows  moves  upward  from  the  pressure  and  the 
valve  opens  so  that  air  can  escape,  the  valve  closing  by  the  lower 
bellows  or  float  as  soon  as  this  is  heated  by  steam  or  lifted  by 


A,  Sylphon  Air  Valve.  B,  Sylphon  Air  and  Vacuum  Valve. 

FIG.  87.— Sylphon  Air  Valves. 

water.  When  a  vacuum  is  formed  in  the  radiator  the  valve  is 
held  closed  by  the  excess  of  pressure  on  the  outer  part  of  the 
upper  bellows. 

m  For  venting  the  whole  system  at  the  end  of  a  return  line 
the  Sylphon  Vent  Valve,  Fig.  88,  is  used.  In  this  the  inner 
sylphon  is  closed  and  filled  with  a  fluid  which  operates  to  close 
the  upper  valve  by  pushing  it  upward  against  the  seat  and  the 
outer  sylphon  operates  to  close  the  vent  as  soon  as  the  pressure 
in  the  pipe  line  becomes  equal  or  less  than  atmospheric  pressure. 
The  cylinder  within  the  lower  sylphon  is  to  keep  this  from 
closing  too  much  when  cold. 


RADIATORS,   VALVES  AND  HEAT  TRANSMISSION      105 

Heat  Transmission  through  Radiators.  Radiators  trans- 
mit heat  by  conduction  to  the  outer  surface  of  the  wall;  from  this 
point  it  is  transmitted  by  radiation  to  objects  around  and  by 
convection  to  the  air.  The  radiant  energy  emanates  in  all 
directions,  and  hence  for  the  ordinary  radiator  the  large  part  of 
the  surface  cannot  radiate  heat  to  the  outside  objects,  as  this  heat 


FIG.  88.— Sylphon  Air  Vent  Valve. 


is  intercepted  by  the  other  sections  of  the  radiator.  Newton  was 
one  of  the  first  to  state  a  law  for  radiant  energy,  and  he  was 
followed  by  Dulong  and  Petit,  Rosetti,  Stefan,  Weber,  Bottomley, 
Paschen  and  Petavel,  extending  from  1690-1898.  Most  of 
these  give  radiation  in  the  form  H  —  K(Tia  —  T2a)  where  K  is 
the  constant  of  radiation  and  T\  and  T2  are  the  absolute  temper- 
atures of  the  hot  body  and  the  surrounding  cold  bodies  respect- 


106         ELEMENTS  OF  HEATING  AND  VENTILATION 

ively.     The  values  of  a  vary  according  to  the  different  investi- 
gations, 

a  =  i,  Newton; 

a  =  3,  Rosetti; 

a  =  4,  Stefan; 

a  =  5.  7,  Bottomley,  Paschen; 

a  =  5,  Petavel. 

According  to  Dulong  and  Petit  the  expression  is 

H  =  KCT, 
and  to  Weber, 

H  =  KTCT. 

Stefan  from  experimental  data,  and  Boltzmann  from 
thermodynamic  reasoning  independently  determined  that  the 
energy  radiated  from  a  black  body  is  proportional  to  the  fourth 
power  of  the  absolute  temperature,  or 


E  =  radiated  energy  per  square  foot  per  hour; 
K  =  SL  constant; 

T  =  absolute  temperature  of  radiating  body; 

T0  =  absolute  temperature  of  receiving  body. 

In  English  measures  X  =  (i6Xio~10). 

This  is  known  as  the  Stefan-Boltzman  radiation  law,  and 
refers  truly  to  a  black  body;  but  since  the  heat  reflected  and 
radiated  from  a  body  is  equal  (by  the  Stewart-Kirchhoff  law)  to 
that  emitted  from  a  black  body,  this  rule  may  be  applied  if 
necessary  to  any  body.  It  represents  the  best  law  of  radiation. 

Carpenter  states  that  the  larger  part  of  the  heat  transmitted 
from  a  radiator  is  due  to  convection,  and  this  is  reasonable  as 
pointed  out  before  on  account  of  interference.  From  experi- 
ments of  Ser  and  others  as  mentioned  by  Dalby  in  London 
Engineering,  Oct.  22,  1910,  and  from  the  discussion  of  this 
paper  by  Nicholson,  as  well  as  by  his  experiments  and  those 
performed  by  the  makers  of  indirect  heaters,  it  is  evident  that 


RADIATORS,  VALVES  AND  HEAT  TRANSMISSION     107 

the  amount  of  heat  removed  from  a  radiator  depends  on  the 
velocity  of  the  air  passing  it. 

The  air  seems  to  wipe  the  heat  from  the  surface.  There  is 
apparently  a  film  of  air  in  contact  with  the  heating  surface 
which  prevents  the  transmission  of  heat,  as  its  conductivity  is 
low,  and  so  long  as  it  remains  in  contact  with  the  surface  it  cuts 
down  the  temperature  difference  between  the  air  to  be  warmed 
and  the  conducting  substance,  which  in  this  case  is  the  air  film. 
By  causing  the  air  to  pass  rapidly  over  the  metal  surface  or  to 
impinge  on  it,  the  thickness  of  the  film  is  decreased,  the  true 
temperature  difference  increased,  and  the  amount  of  heat 
transference  is  thus  increased. 

The  data  seem  to  show  that  the  heat  transference  at  any 
place  is  given  by  the  forms: 

H=fV~,(ts-ta)A        .    .    .    .'  .    ;    .    .    .    .'   .    (51) 
or 

H  =  (B+C9v)(ts-ta)A (52) 

v  =  velocity  in  feet  per  second; 

ts  =  temperature  of  steam  or  hot  water  in  deg.  F. ; 

ta  =  temperature  of  air  in  deg.  F. ;  j 

A  =area  in  square  feet; 

f,  C,  B,  constants; 

p=  density. 

For  a  given  velocity  v,  the  quantity  of  heat  given  off  by  the 
area  dA,  is 

dH  =  Ki(t,-i)dA,     .    .:    .,    .    .    .<    (53) 

where  K\  is  a  constant,  although  by  some  it  is  considered  to 
depend  on  /. 

The  quantity  /  will  vary  between  the  two  limits  h  and  fe 
as  the  area  varies  between  o  and  A . 

(54) 


108         ELEMENTS  OF  HEATING  AND  VENTILATION 
Now 


M  =mass  of  air  heated  per  hour; 
cp   =  specific  heat  of  air  ; 
H  =  Mcp(t2-h) 

(Variation  in  cp  not  appreciable  over  this  range.) 

/2  =  temperature  of  air  leaving  radiator; 
/i  =  temperature  of  air  entering  radiator. 
Hence 

(55) 


(56) 

Now 

rr 

Mcp  =  -   -. 


Hence 

t,-ti 


and  substituting  in  (54) 


(57) 


or 

g=^i  /2,~_U •":.-  -(58) 


RADIATORS,  VALVES  AND  HEAT  TRANSMISSION     109 
If  the  term  involving  velocity  is  introduced  this  becomes 


(59) 


Now  in  general  the  formula  used  for  heat  transmission  is 

H  =  K(ts-tr}A.       .  ..     ......      (60) 

where  U  =  temperature  of  the  room  or  the  mean  temperature 
of  the  air  in  an  indirect  heater.  Comparing  this  with  (54)  it 
is  seen  that  K  must  be  of  the  form 


It  is  seen  that  K  will  vary  with  v,  tsj  /2,  h  and  tr.     In  case  of 
direct  radiation  tr  =  h,  while  in  indirect  radiation 


*  If  the  transmission  depends  on  a  power  of  the  temperature  difference  the 
following  results: 

dH  =  f-^fii  (t,  ~t)dA=  MCpdt. 

(ts  —  t) 

K1dA=Mcp(ts-t)n-Idt. 


Now                                   H=Mcp(t2-t1). 
Hence  U=-f ^ — - 


Now 


This  holds  for  all  valus  of  n  except  for  n  —  0.     This  was  the  value  used  above. 


110         ELEMENTS  OF  HEATING  AND  VENTILATION 

Because  of  the  complication  of  this  formula,  experimental 
determination  of  the  quantity  K  is  made  without  finding  KI 
and  computing  K. 

In  performing  the  experiment  the  radiator  is  supplied  with 
steam,  the  quality  and  pressure  of  which  are  determined  by 
instruments,  and  the  temperature  and  weight  of  the  condensate 
is  found.  From  the  data  H  is  given  by 

E  =  M  (q +xr  -  q0)  =  M(i  -  q0) , 
where 

M  =  weight  of  steam  condensed  per  hour; 

i  =  heat  content  of  entering  steam ; 
<7<>  =  heat  content  of  leaving  steam. 

Knowing  A\,  ts  and  ta,  the  quantity  K  may  be  found. 

In  direct  radiators  the  velocity  v  is  about  the  same  in  radiators 
of  the  same  type,  and  so  there  will  not  be  much  difference  in  K 
for  different  conditions.  But  on  account  of  the  height  and  posi- 
tion of  the  radiating  surface  causing  a  difference  in  this  quantity 
a  change  is  expected  in  the  value  of  K  for  differing  radiators. 
The  kind  of  surface  would  affect  K,  so  that  wrought  iron,  cast 
iron,  painted  radiators  and  bronzed  radiators  are  all  expected 
to  give  varying  values  of  K. 

The  effect  of  radiation  is  present  principally  on  the  edges  of 
the  center  sections  and  from  the  faces  of  the  end  sections, 
and  as  a  result  of  this  the  value  of  K  is  greater  for  radiators 
of  a  few  sections  or  coils  than  for  those  having  a  number  of 
sections.  The  formula  shows  clearly  that  tS)  hj  h  and  ta  affect 
K,  and  so  in  reality  there  should  be  a  variation  in  this  quantity 
for  different  steam,  water  and  air  conditions. 

Carpenter  quotes  tests  giving  K  from  1.23  to  1.97,  while 
Rietschel  gives  values  in  his  tables  as  low  as  0.51  and  as  high 
as  2.65  with  steam  in  a  single  pipe. 

With  a  single  section  Denton  and  Jacobus  found  a  constant 
as  high  as  2.39,  while  with  a  series  of  sections  the  value  1.97  was 
obtained.  In  another  case  2.24  for  a  single  section  was  reduced 
to  1.30  when  9  were  used. 


RADIATORS,  VALVES  AND  HEAT  TRANSMISSION      111 

The  condition  of  the  surface  of  the  radiator  effects  the  amount 
of  transmission.  Experiments  have  been  made  by  Carpenter 
and  by  Allen,  and  these  seem  to  show  that  bright  paints 
would  decrease  the  efficiency  of  transmission  while  dark  paints 
or  even  white  lead  increased  the  efficiency.  In  regard  to  bronz- 
ing, their  results  differed  :  Carpenter  found  an  increase  while 
Allen  reports  a  decrease  in  efficiency.  The  number  of  coats  of 
paint  did  not  seem  to  effect  this  result,  the  outer  coat  being  the 
determining  factor. 

The  results  of  experiments  show  that  the  radiator  of  large 
surface,  long  or  high,  will  give  a  smaller  rate  of  transmission, 
K,  than  a  small  radiator. 

Considering  all  results  it  will  be  well  to  take  K  as  1.75  * 

Then       #  =  1.75(222  —  70)  =  265  for  low  pressure  steam; 
.  ---  —  70  )  =  160  for  hot  water. 

In  the  case  of  low  pressure  steam  the  pressure  is  assumed 
to  be  3  Ibs.  gage,  and  for  the  hot  water,  the  water  is  supposed 
to  enter  at  170°  F.  and  leave  at  150°  F. 

With  indirect  heaters  the  effect  varies  with  the  velocity. 
The  usual  method  is  to  use  the  formula, 


According  to  Carpenter, 


. 

•o  —  average  velocity  over  coils  in  feet  per  second  ; 
ts  =  steam  temperature; 
U  =  inlet  temperature; 
t0  =  outlet  temperature. 

*  Rietschel  gives  the  following  values  of  K,  according  to  Kinealy:  gas  to  air 
through  clay  plate  1.09,  gas  to  air  through  cast  or  sheet  iron  1.4  to  2.0,  gas  to 
water  or  reverse  through  cast  or  sheet  iron  2.6  to  4.0,  steam  to  air  through 
cast  or  wrought  iron  2.2  to  3.6,  steam  to  water  through  metal  166  to  200. 


112 


ELEMENTS   OF  HEATING  AND  VENTILATION 


RADIATORS,  VALVES  AND  HEAT  TRANSMISSION      113 


X 


S     I 


1  = 


S    Pi   o 


M 


*   S  °, 

I; 
s.  > 


1    > 


114 


ELEMENTS  OF  HEATING  AND  VENTILATION 


0       100     200     300     400     500     600     700     800     900     1000    1100    1200    1300    1400 
Velocity  in  Feet  perMin. 

(a)  Entering  Air  at  o°  F. 


240r 
220 
200 
•18o| 
160 
|  140 
120 1 


X 


0       100     200     300     400     500     600      700     800     900     1000   1100    1200    1300    1400 
Velocity  in  Feet  per  Min. 

(Z>)  Air  Entering  at  20°  F. 

FIG.  91. — Outlet  Temperature  from  Buffalo  Forge  Heaters  of  Four  Coils  to  the 
Section  with  Steam  at  5  Ibs.  Gage  Pressure. 


RADIATORS,   VALVES  AND  HEAT  TRANSMISSION      115 


100     200      800     400     500     600      TOO     800     900     1000    1100    1200    1300    1400 
Velocity  in  Feet  per_Miru 

(c)  Entering  Air  at  40°  F. 

FIG.  91.— Outlet  Temperature  from  Buffalo  Forge  Heaters  of  Four  Coils  to  the 
Section  with  Steam  at  5  Ibs.  Gage  Pressure. 


1000 
900 
800 
700 


GOO 


^;5 

- 


400 


5200 
100 


„_, 


100     200      300     400      500      600      700     800      900     1000   1100    1200    1300    1400 
Velocity  in  Ft.  per  Min. 

(a)  Entering  Air  at  o°  F. 

92> — Heat  Transmitted  per  Lineal  Foot  of  i  Inch  Pipe  at  Different  Velocities 
with  Various  Sections  of  4  rows  of  Pipe  each,  Steam  being  at  5  Ibs.  Gage 
pressure  and  Entering  Air  at  o°  F.,  20°  F.  and  40°  F.  Velocity  at  70°  F. 


116 


ELEMENTS  OF  HEATING  AND  VENTILATION 


AOOO 


900 


800 


700 


^'500 


400 


300 


JXX) 


100 


1000 


900 
800 
700 
600 

3500 
« 
400 

300 
200 
100 


100      200     300     400      500      600     700     800     900     1000    1100  1200    1300   1400 
Velocity  in  Ft  per  Min. 

(b)  Entering  Air  at  20°  F. 


1000    1100    1200    1300    1400 


100      200      300      400      500      600      TOO      800      900 
Velocity  in  Ft.  per  Min. 

(c)  Entering  Air  at  40°  F. 

FIG.  92. — Heat  Transmitted  per  Lineal  Foot  of  i  Inch  Pipe  at  Different  Velocities 
with  Various  Sections  of  4  rows  of  Pipe  each,  Steam  being  at  5  Ibs.  Gage 
pressure  and  Entering  Air  at  o°  F.,  20°  F.,  and  40°  F.  Velocity  at  70°  F* 
(Curves  constructed  from  data  published  by  Buffalo  Forge  Co.) 


RADIATORS,  VALVES  AND  HEAT  TRANSMISSION      117 


The  Buffalo  Forge  Company  give  tables  to  be  used  with  their 
heating  coils  of  pipe,  and  the  American  Radiator  Company 
give  results  of  tests  with  their  vento  heater  sections.  These 
curves  give  the  temperature  increase  for  different  velocities. 
These  have  been  plotted  as  curves  shown  in  Figs.  89,  90, 
91,  92,  which  may  be  used  for  computing  areas  required  for 
indirect  radiators.  These  curves  and  the  formula  of  Carpenter 
give  for  values  of  K  the  following: 


Velocity 
in  Ft.  per  M. 

Carpenter 
K. 

I  Section  of 
4  Coils. 

3  Sections  of 
12  Coils. 

i  Vento. 

3  Vento. 

600 

6.1 

7-1 

7-7 

7-1 

6.6 

800 

6.7 

9.6 

9.2 

8-3 

7-9 

1000 

7-3 

II  .2 

10.7 

9-3 

9-0 

I2OO 

7-8 

12.4 

n.  8 

10.4 

IO.O 

I4OO 

8-3 

I3.2 

12.5 

II  .2 

10.8 

l6oO 

8.6 

13-7 

13.0 

ii.  8 

n-5 

These  results  indicate  that  a  formula  such  as  that  of  Carpenter 
does  not  hold  as  K  is  a  function  of  the  temperature  drop 
along  a  set  of  surfaces,  hence  it  is  best  to  use  a  set  of  charts  simi- 
lar to  those  given. 


CHAPTER  V 

METHODS  OF  CALCULATING  HEAT  REQUIRED  FOR  ROOMS 

THE  methods  used  in  practice  for  finding  the  heat  loss  in 
rooms  varies  according  to  the  engineer.     In  any  case  a  system 


BDG  ROOM  LOCATION  _.. 

No. 

CEILING  FT, 

WALL 

KIND 

THICK 

AREA 

AT 

C 

Ex.  C. 

HEAT  LOSS 

CEIL. 

FLOOR 

SKETCH 
N 

W                                   E 

S 

VOLUME          _      _Cu.  FT. 

OCCUPANTS  N 

AIR  SUPPLY— 

^.CH^* 
FLUES 

TOTAL 

VENTILATION 

>.-                  HT. 

...A 

.  .__  _CU.KT. 

HEATING  SURFACE 

KIND 

MAKE 

SQ.FT.    ST.  D 

FIG.  93.— Data  Sheet. 

of  calculation  should  be  used  which  will  give  results  in  a  direct 
manner  and  one  in  which  these  may  be  readily  checked.  One 
method  is  to  have  ruled  pages  in  a  book  with  entries,  as  shown 
in  Plates  I,  II.  A  certain  part  of  the  page  is  used  for  one  room, 

118 


CALCULATING  HEAT  REQUIRED  FOR  ROOMS 


119 


and  the  data  for  the  room  is  taken  from  plans  and  entered. 
Another  form  used  by  the  late  Prof.  H.  W.  Spangler  is  shown 
in  Fig.  93.  To  fill  out  sheets  in  either  method  the  plans  of  the 
building  to  be  heated  are  first  studied  and  the  rooms  are  given 
designating  numbers,  and  beside  the  numbers  the  desired  or 
assumed  mean  temperature  of  the  room  is  marked.  The  points 


FIG.  94. — Cellar  Plan. 

of  the  compass  are  marked  and  then  the  data  required  on  the 
sheets  are  filled  out. 

To  illustrate  the  method  of  work  the  plans  of  a  two-storied 
house,  with  the  first  story  of  brick  and  the  second  story  of 
shingles,  shown  in  Figs.  94  to  98,  will  be  considered. 

The  temperature  of  the  attic  will  be  taken  as  26°  F.  and  of 
the  cellar  as  36°  F.  The  ceilings  as  shown  by  the  section  are 
not  high,  and  no  allowance  must  be  added  to  the  temperature 
at  head  level  to  allow  for  excessive  height  of  story. 

The  slanting  roof  is  of  shingles  without  sheathing  or  paper 
and  the  deck  roof  is  sheathed  with  wood  on  which  is  a  metal 


120          ELEMENTS  OF  HEATING  AND  VENTILATION 


0 


i 


O 

d 

,j 

-j  ° 

s  s 
^  i 

*  s 

PC 


for 


1 


Is 


1 

I 


1  2 

u     , 


6    dod 


<r°: 

0  0 


-L^-T^ 


go 

"o   * 


O-OOQ 


o-^^-«o 

(<l  CM  CM  CM 

o'do'd 


I'? 


to 


'     * 


o  58S 


0     0 

-•      0 


Q 


22    2    g-o      2 


06    o 


a-    2 


J 

J 

I'o 


i-o 


00  O 

SS       * 


00  Q 


^00^00 


Col- 

is 


00  60* 


oo 


?    = 
V    <\i 


CALCULATING  HEAT  REQUIRED  FOR  ROOMS 


121 


OJ 


V? 

VJ     i 
^    c^ 


-    e* 

0      - 

V  I 


-    U) 
0 


I 


0    £ 


0 

I. 

*3 

"o    ° 


.00 


1 


3 


o  o 

§8 

COc* 


s^ 

5 


Oo 


oo 

•«o 


0      0 

SW      0 
»~       (0, 


23   ?- 
tt 


00  o 


o  o 


S3 


•a*    2  - 


SS 


SS 


-Sfe 
IP 


00 


o  o 


o  0 
00 


O  O      M 
cJrf    rf 

O  0       O 


00       N 

fJ«^      M 

0*6   o 


r4          o* 


<at^         % 


S3    § 


00 


—  to 

00 


0><vt 


ow 


<ao 

Mot 


MO 

*sl 


^>^ 
O  «a 


< 


*4>       0 
.T       fM 


00          * 


n 


122 


ELEMENTS  OF  HEATING  AND  VENTILATION 


cover.  The  first  floor  is  composed  of  ship  lap  over  which  build- 
ing paper  is  placed  and  on  top  of  this  is  a  layer  of  tongued  and 
grooved  flooring.  There  is  no  plaster  below.  The  second 
floor  is  similar  to  this  with  plaster  on  the  lower  side  of  the  joists, 
while  the  attic  floor  is  composed  of  ship  lap  only  with  plaster 


FIG.  95.— First  Floor  Plan. 

below  the  joists.  The  values  of  K  taken  for  these  are  0.23  for 
the  first  floor  and  0.22  for  the  attic  floor  or  ceiling  of  the  second 
floor,  as  the  heated  room  is  below,  see  page  65.  The  second 
floor  is  not  considered  as  the  temperature  is  the  same  on  both 
sides;  but  had  the  second  floor  been  15°  lower  in  temperature, 
the  value  of  K  used  here  for  the  ceiling  of  the  first  floor  and  floor 
of  the  second  story  would  have  been  0.16.  If  the  second  story 


CALCULATING  HEAT  REQUIRED   FOR  ROOMS 


123 


were  15°  higher  in  temperature . than  the  first  floor,  then  the 
value  of  K  would  have  been  0.03,  as  the  hot  room  would  be 
above. 

The  first  floor  walls  are  made  of  8  ins.  of  brick  work,  a  f  in. 
air  space  and  i  in.  of  lath  and  plaster,  hence,  from  page  64, 
the  value  of  K  is  0.24.  The  second  story  is  sheathed  with  ship 
lap  on  which  shingles  are  placed  over  two  layers  of  paper;  the 


FIG.  96.— Second  Floor  Plan. 

value  of  K  is  therefore  0.20.  The  glass  has  a  value  of  K  of  0.96. 
The  doors  on  the  outside  and  the  French  windows  are  considered 
as  having  the  same  values  as  glass. 

The  temperature  of  the  attic  could  have  been  worked  out 
by  the  method  given  by  Eq.  (39), 

0.22(70-4)  =0.4(^-0°). 
In  the  equation  above  the  value  of  K  for  the  roof  is  taken 


124          ELEMENTS  OF  HEATING  AND  VENTILATION 

as  0.4;     ta  is  the  temperature  of  the  attic.     In  this  case,  the  solu- 
tion of  the  equation  gives 


With  a  thicker  roof  or  one  sheathed  and  with  paper  beneath 


FIG.  97.  —  Section. 

the  shingles,  the  value  of  K  would  equal  0.3,  and  then  the  equation 
would  give 


The  drawings  of  the  building  are  now  taken  and  the  various 
rooms  are  marked  with  distinguishing  numbers,  and  beneath 
these  numbers  the  temperatures  to  be  expected  and  the  changes 
per  hour  if  the  ventilation  is  figured  in  this  way.  In  numbering 
rooms  in  large  buildings  it  is  well  to  use  combinations  of  numbers 
to  designate  floors.  Thus  all  numbers  beginning  with  100, 


CALCULATING  HEAT  REQUIRED   FOR  ROOMS 


125 


as  105,  120,  132,  etc.,  are  found  on  the  first  floor,  while  320, 
318,  306  are  found  on  the  third  floor. 

The  table  is  now  filled  in,  the  number  of  the  room,  then  a 
rough  sketch  of  the  same,  showing  the  form  of  the  room,  then 


a  column  for  heights  and  volumes  and  then  a  column  giving 
the  occupants  or  the  number  of  changes  per  hour.  The  sketch 
is  made  with  the  north  side  to  the  top  and  the  windows  and 
doors  designated  by  heavier  lines.  It  is  also  well  to  mark 
temperatures  on  the  various  sides  of  the  room. 


126          ELEMENTS  OF  HEATING  AND  VENTILATION 

The  losses  for  the  various  sides  of  the  room  are  now  filled  out 
with  the  floor  and  ceiling,  giving  the  total  area,  glass  or  door 
area,  net  wall  area,  difference  in  temperature,  value  of  the 
coefficient  and  finally  the  factor  which  is  to  care  for  exposure. 

For  high  rooms  the  effect  of  increased  temperature  required 
would  be  shown  in  a  greater  temperature  difference.  The 
fact  that  increased  radiation  might  be  needed  for  intermiitent 
heating  would  be  shown  in  column  headed,  "  Remarks." 

By  multiplying  together  the  area,  constant,  temperature 
difference  and  factor,  the  amount  of  heat  required  for  each  side 
is  found  and  entered  in  the  heat  column.  The  sum  of  all  heats 
excepting  that  for  the  ventilating  air  is  placed  in  the  total  heat- 
column,  with  the  ventilating  heat  as  a  separate  item.  These 
various  columns  may  be  added  together  by  floors  giving  totals 
which  are  used  in  making  checks. 

In  applying  this  method,  although  outside  doors  are  taken 
as  equal  to  windows,  they  in  reality  have  a  much  lower  constant, 
and  for  that  reason  on  interior  work  or  in  any  place  not  exposed 
to  the  wind,  their  true  values,  given  in  Chapter  III,  may  be 
used. 

The  application  of  the  table  described  above  will  vary  with 
various  systems  and  will  be  considered  in  the  succeeding  chapters. 


CHAPTER  VI 
DIRECT  STEAM  HEATING 

IN  direct  steam  heating  the  steam  is  carried  to  the  radiators 
on  the  different  floors  in  several  ways. 

Fig.  99  illustrates  the  single  pipe  system.  In  this  method 
of  arranging  piping,  the  steam  flows  from  the  boiler  through 


FIG.  99. — Single  Pipe  System. 

the  main  and  risers  to  the  various  radiators.  After  condensa- 
tion the  water  falls  back  through  the  radiators  and  rises  into 
the  main.  The  main  is  carried  around  the  basement  pitching 
in  the  direction  of  flow  until  it  drops  below  the  water  line  of 
the  boiler.  In  this  system  the  radiators  are  each  provided 

127 


128 


ELEMENTS   OF  HEATING  AND  VENTILATION 


with  an  air  valve  on  the  opposite  side  from  the  inlet.  The 
system  is  not  as  positive  as  the  two-pipe  system  of  Fig.  100, 
but  the  pipes  are  fewer  in  number.  Although  larger  pipes  are 
required,  the  cost  is  less  than  the  two-pipe  system.  This  system, 
unless  very  carefully  installed,  is  a  noisy  one,  owing  to  the  water 
hammer. 

In  the  double-pipe  system  of  Fig.  100  separate  steam  risers 
and  return  risers  are  connected  in  the  basement  to  the  steam 
main  and  the  return  main  respectively. 


FIG.  ioo. — Two-pipe  System. 

The  connections  to  the  risers  are  made  so  that  no  pockets 
will  form  and  each  riser  is  controlled  by  a  valve. 

This  system  has  the  advantage  that  the  condensation  is 
cared  for  by  a  separate  line  and  does  not  travel  in  the  same 
pipe  as  the  steam.  This  double  flow  in  the  same  pipe  may 
cause  hammering  when  the  system  is  started.  Air  valves  are 
required  to  relieve  the  air  which  may  be  held  in  the  top  of 
a  radiator,  as,  after  a  very  short  time,  the  supply  and  return 
pipes  are  filled  with  steam.  This  is  the  objection  to  this  system 


DIRECT  STEAM  HEATING  129 

with  ordinary  valves.  The  steam  in  the  return  pipe  will  feed 
a  radiator  even  after  the  supply  valve  is  closed  unless  the  return 
valve  is  shut  also.  The  pressure  in  the  return  pipe  causes  a 
sluggish  circulation  at  times.  To  overcome  this  such  valves  as 
the  auto  valve  of  the  Thermograde  Co.,  the  seal  valve  of  Warren 
Webster  &  Co.,  the  seal  valve  of  the  Monash  Co.,  or  a  similar  one 
is  used  on  the  return.  In  this  way  there  is  no  pressure  in  the 
return  and  the  circulation  is  positive.  Warren  Webster  &  Co. 
use  a  vacuum  pump  on  their  return  pipe  in  their  system,  thus 
carrying  so  low  a  pressure  that  the  steam  in  the  supply  pipe  is 
practically  at  atmospheric  pressure.  This  is  of  advantage  when 
the  exhaust  from  engines  is  used,  as  the  back  pressure  on  the  engine 
is  not  great  and  there  is  little  pitch  to  the  return  pipe. 
Unless  a  valve  of  the  type  of  these  return  valves  were  used  it 
would  not  be  possible  to  keep  the  pressure  at  such  a  low  point 
in  the  return.  This  system  is  known  as  the  vacuum  system. 

Another  system  of  distributing  the  steam  is  that  of  the 
overhead  distributing  main  or  Mills*  system,  Fig.  101.  In  this 
the  steam  is  carried  through  a  riser  A  to  the  distributing  main 
B  in  an  attic  or  upper  floor  of  a  building.  From  this  the  risers 
C  are  taken  off.  The  return  risers  D  are  carried  downward  and 
connect  to  the  return  main  F.  The  condensation  in  the  steam 
risers  C  is  collected  in  the  drip  line  E,  although  at  times  these 
drips  are  put  into  the  return  main  or  the  condensation  is  cared 
for  by  the  lowest  radiator.  These  two  latter  methods  are  not 
good  and  that  shown  in  Fig.  101  should  be  used  in  caring  for 
the  drip.  In  such  a  case  the  drip  line  is  connected  to  the  return 
through  a  steam  trap. 

For  high  buildings  this  system  is  often  employed  with  the 
distributing  main  near  the  middle  of  the  height  of  the  building, 
steam  being  distributed  up  and  down  from  that  point. 

The  same  system  is  used  with  a  single  riser  system  at  times, 
the  riser  being  connected  to  the  distributing  main  above  and  the 
return  main  below.  The  drip  is  eliminated  in  this  case  and 
so  are  the  return  risers.  This  is  sometimes  called  the  complete 
circuit  system  and  the  one  pipe  system. 

In  many   small   steam   installations   the   complete  heating 


130 


ELEMENTS  OF  HEATING  AND   VENTILATION 


system  is  connected  to  a  boiler  without  the  use  of  a  pump,  as 
shown  in  Fig.  2,  and  in  such  a  case  the  drip  of  Fig.  101  is  not 
necessary.  The  method  just  described,  of  a  single  riser  system 
with  an  overhead  distribution,  is  quite  good,  as  the  circulation 
is  positive  in  the  supplies,  especially  if  the  return  is  sealed  by 


FIG.  101. — Mills  System. 

dropping  the  pipe  below  the  water  line  by  a  vertical  leg.  In 
cases  of  central  station  heating,  where  returns  from  several 
buildings  are  delivered  into  a  common  return  pipe,  it  is  well  to 
allow  each  building  to  discharge  through  a  trap  into  the  main 
return  pipe.  If  this  is  not  done  one  building  may  interfere 
with  the  proper  heating  of  another.  The  return  from  one 


DIRECT  STEAM  HEATING  131 

building  may  prevent  the  air  from  being  driven  out  of  another 
one. 

To  find  the  size  of  radiators  required  for  any  room,  the  heat 
found  in  Plates  I  or  II  is  divided  by  the  heat  transmission  per 
square  foot  of  heating  surface  as  found  in  Chapter  IV.  A 
simple  number  to  remember  for  low  pressure  steam  heating  is 
250  B.t.u.  per  square  foot  per  hour.  Dividing  the  amount 
of  heat  in  the  case  mentioned  above  by  this,  the  amount  of 
heating  surface  is  found. 

To  check  the  results  of  computation  it  is  well  to  divide  the 
cubic  capacity  of  the  various  rooms  by  the  square  feet  of  radiation 
in  them,  obtaining  the  cubic  feet  of  space  heated  by  one  square 
foot  of  heating  surface.  This  quantity  varies  with  different 
kinds  of  construction  and  amount  of  window  space,  but  the  num- 
bers serve  to  check  any  large  errors  after  the  designer  has  had 
experience.  To  guide  the  student  the  following  table  has  been 
prepared  from  various  sources: 

CUBIC    FEET  OF  VOLUME  PER   SQUARE   FOOT  OF 
DIRECT   RADIATION 

Residences: 

Living  rooms : 35  to    60 

Sleeping  rooms 50  to    80 

Offices 40  to    80 

Schools 40  to    80 

Factories 75  to  100 

Assembly  halls '...... 75  to  100 

Hotels 75  to  100 

Stores 75  to  100 

Churches 125  to  200 

Auditoriums 125  to  200 

Gymnasiums 100 

Work  shops , .  150 

From  the  table  of  Chapter  IV,  the  numbers  of  sections  of 
different  forms  of  radiators  required  for  these  amounts  of  heating 
surface  are  found.  The  height  of  the  radiator  is  fixed  by  the 


132 


ELEMENTS  OF  HEATING  AND  VENTILATION 


condition  in  the  building,  such  as  heights  of  window  sills,  etc. 
The  selections  for  the  building  computed  in  Chapter  V  are 
shown  in  the  tables  of  that  chapter.  Radiators  are  usually 
placed  in  front  of  windows  to  cause  a  blanket  of  hot  air  in  front 
of  the  window  and  to  heat  the  leakage  air.  They  should  not 
extend  above  the  sill. 

Some  authorities  prefer  to  put  them  on  a  wall  near  a  window, 
but  not  in  front  of  it,  claiming  that  in  this  way  there  is  no  down 
current  of  cold  air  to  interfere  with  the  up  current  of  hot  air. 
The  cold  air  drops  from  the  window,  passes  to  the  radiator,  and 
there  is  a  strong  rising  current  aiding  in  the  heat  transference. 
There  are  two  objections  against  this:  valuable  wall  space 
for  furniture  is  taken,  and  there  will  be  cold  drafts  from  the 
window. 

The  radiators  being  selected,  the  size  of  outlets  should  be 
fixed.  These  are  standardized  by  the  radiator  companies  and 
are  given  in  the  table  below : 

TAPPING  FOR  RADIATORS 


Single  Pipe. 

Two  Pipe  Steam. 

Hot  Water. 

Sq.ft.  Area. 

Tapping. 

Sq.ft.  Area. 

Supply. 

Return. 

Sq.ft.  Area. 

Supply. 

Return. 

24 

i    in. 

48 

I 

t 

40 

I 

I 

24-60 

it   " 

48-96 

ji 

I 

40-72 

it 

it 

6o-lOO 

i    « 

96 

if 

it 

72 

100 

2        '' 

The  connections  from  the  radiator  to  the  risers  should  be 
arranged  so  that  as*the  riser  expands  and  contracts,  the  radiator 
will  not  be  lifted  from  the  floor.  The  best  way  to  arrange 
these  branches  is  shown  in  Fig.  102,  an  isometric  drawing.  The 
isometric  method  of  representing  piping  is  very  useful.  In 
this  the  vertical  lines  represent  vertical  pipes;  horizontal  lines, 
those  parallel  to  the  plane  of  the  drawing;  and  lines  at  30°, 
lines  perpendicular  to  the  plane  of  the  paper.  Single  lines  are 
used  to  represent  the  pipes,  and  these  may  be  solid  or  dot  and  dash 
lines.  Thus,  Fig.  104,  represents  four  ways  of  connecting  radi- 


DIRECT  STEAM  HEATING 


133 


FIG.  102. — Branch  Connection. 


Up 


Out 


*-- 


FIG.  103. — Isometric  Directions.          FIG.  104. — Radiator  Connections. 


134 


ELEMENTS  OF  HEATING  AND  VENTILATION 


ators.  The  third  method  should  never  be  used,  as  the  expan- 
sion of  the  riser  will  lift  the  radiator  and  this  tends  to  break  the 
fittings  at  radiator  if  it  does  not  actually  break  them.  The  second 
method  is  satisfactory  if  the  branch  is  long  enough  to  have 
some  spring,  and  in  the  first  or  best  method  there  is  a  chance 
for  the  branch  to  swivel  on  the  ells  and  care  for  the  expansion. 


r 


LOOKING  NORTH 


LOOKING  EAST 


D 


b  I*" 


LOOKING  SOUTH  LOOKING  WEST 

FIG.  105. — Development  of  House. 

Risers  are  usually  arranged  so  that  a  number  ot  radiators 
come  on  the  same  line.  This  cuts  down  the  number  of  risers 
and  gives  a  cheaper  job.  To  study  the  distribution  properly 
and  to  give  the  heating  contractor  a  knowledge  of  what  is  to  be 
done  it  is  well  to  make  a  small  scale  drawing,  usually  TV  in. 
to  the  foot,  showing  the  development  of  the  walls  of  the  building, 
with  windows  and  partitions  marked  on  it,  and  on  this  lay  out 


DIRECT  STEAM  HEATING 


135 


the  radiators  and  risers.  These  views  are  all  from  the  inside 
of  the  building,  showing  the  wall  as  seen  from  the  room.  Fig. 
105  shows  such  a  development  for  the  house  figured  in  Chapter 
V.  On  this  view  the  radiators  are  placed  and  each  radiator 
and  riser  is  given  a  designating  mark.  The  radiators  are  marked 
with  the  number  of  the  room  followed  by  small  letters  a,  b,  c, 
d  and  e,  if  there  are  more  than  one. 

Thus  in  room  5  there  are  two  radiators,  50  and  56.  The  risers 
are  marked  A,  B}  C,  D  and  E,  or  by  some  other  method,  as 
I,  II,  III,  IV,  etc.  The  radiators  and  risers  are  also  marked 
on  the  plans.  Care  must  be  taken  in  placing  these  to  see  that 
there  is  no  interference  with  the  placing  of  the  furniture.  Where 
possible  the  heating  engineer  should  consult  with  his  client 
about  the  placing  of  radiators. 

The  risers  are  usually  proportioned,  by  the  number  of  square 
feet  of  radiation  on  them,  and  the  table  below  gives  the  size  for 
various  amounts  of  radiation  as  recommended  by  Carpenter 
and  others. 


RISERS  FOR  VARIOUS  HEIGHTS  OF  BUILDING 


Radiator 

Radiator 

Surfaces 

Low. 

Medium. 

High. 

Surfaces 

Low. 

Medium. 

High. 

in  Sq.  Ft. 

in  Sq.  Ft. 

2O 

I 

I* 

ii 

400 

2 

2* 

3 

60 

I* 

I* 

li 

500 

4 

3 

3 

IOO 

il 

I* 

r| 

6oc 

2* 

3 

3j 

2OO 

s| 

2 

2 

700 

3 

3 

3l 

300 

2 

2 

2 

800 

3 

3i 

4 

The  risers  should  be  controlled  by  valves,  so  that  any  radiator  \ 
or  branch  may  be  fixed  without  shutting  down  the  whole  plant. 
The  valves  on  the  risers  leading  to  a  given  radiator  are  closed 
when  necessary  for  the  repair  of  the  radiator  or  connection. 
This  can  be  quickly  done  and  there  is  no  interference  with  the 
radiators  on  other  lines. 

Where  risers  and  vertical  pipes  of  branches  pass  through 
floors  or  where  horizontal  pipes  pass  through  partitions,  floor 
and  ceiling  plates,  Fig.  106,  are  placed  around  the  pipes  to  close 


136 


ELEMENTS  OF  HEATING  AND  VENTILATION 


the  end  of  the  hole  in  the  plaster  and  give  a  neat  finish.  These 
are  sometimes  attached  to  the  ends  of  the  sleeves  which  are 
used  to  surround  pipes  which  pass  floors  and  partitions.  The 


FIG.  106. — Floor  and  Ceiling  Plates. 

sleeves,  Fig.  107,  are  made  of  cast  iron  or  galvanized  iron. 
They  form  an  air  space  around  the  pipe  and  also  ensure  the  pipe 
having  a  chance  to  expand  and  contract  without  breaking  the 
plaster.  By  the  use  of  an  air  space  around  the  pipe  the  chance 


FIG.  107. — Floor  Sleeve. 


FIG.  108. — Pipe  Hangers. 


for  charring  timber  construction,  and   the   resulting  danger  of 
fire  is  removed. 

The  risers  are  supported  by  pipe  hangers,  Fig.  108,  attached 
to  a  top  horizontal  branch  of  the  riser  or  by  band  anchors,  Fig. 
109,  attached  around  the  vertical  feeder.  The  anchor  type  is 
the  better  one  to  employ,  as  this  permits  one  to  support  the  riser 


DIRECT  STEAM  HEATING 


137 


near  the  base  or  at  the  middle  of  its  length.     If  at  the  middle 
the  expansion  occurs  in  each  direction.     If  the  end  of  a  riser 
has  any  expansion  the  connection 
to  the  feed  line  or  return  must  be 
made  to  allow  for  this.     Of  course, 
it    is   possible   for   pipes   to   bend 
sufficiently  to  permit  of  expansion 
if  long  enough,  but  there  is  danger 
of     the    fitting    breaking,    conse- 
quently it  is  well   to   arrange  the 
connection  from  main  to  branch  as 
in  A ,  Fig.  1 10.     If  the  end  of  the 
pipe  is  anchored    the    connection 
may  be  made  as  at  B,  Fig.  no. 
The  connections  A  and.  B,  Fig.  i  io;      FlG'  I09-~clamP  or  Anchor- 
permit  the  main  to  move  without  danger  of  rupture,  as  the  ver- 
tical elbows  will  allow  the  branch  to  swivel .     At  times  45° 


B 


FIG.  no. — Branch  Connections. 


elbows  are  used  to  permit  of  expansion.     Expansion  in  most 
heating  systems  can  be  cared  for  by  swinging  ells,  and  when 


138 


ELEMENTS  OF  HEATING  AND  VENTILATION 


possible  this  should  be  done  or  expansion  bends  or  corrugated 
pipes  should  be  used.  The  slip  expansion  joints  cause  consider- 
able trouble  by  leaking  at  the  packing  in  the  stuffing  box. 

The  expansion  to  be  allowed  for  various  steam  pressures 
is  different.    The  table  below  gives  the  amount  to  be  cared  for 


in  inches  for  each  100  ft.  if  the  original  pipe  is  at  o( 
70°  when  various  steam  pressures  are  used. 


30°,  6o< 


EXPANSION  IN  INCHES 
PER  100  FEET 


Gage  Steam  Pressure. 

Water  Temp. 

Original 

Temperature. 

ISO 

100 

40 

10 

-       5 

212° 

180° 

0 

2.84 

2.63 

2.23 

1.87 

i-77 

I-65 

1.40 

30 

2.6l 

2.40 

2.OO 

1.63 

i-54 

1.41 

I.I7 

60 

2.38 

2.16 

1.76 

1.40 

i   3i 

1.18 

o  93 

70 

2.30 

2.08 

1.69 

1.32 

1.23 

I.IO 

0.81 

The  steam  mains  and  return  mains  are  designed  in  several 
ways.  The  first  method  is  to  use  tables  giving  the  amount  of 
surface  to  be  cared  for  by  mains  of  various  sizes.  These  tables 
are  made  for  lines  of  a  definite  length,  the  usual  length  being 
100  ft. 

CAPACITY  OF  PIPES  IN  SQUARE  FEET  OF  RADIATION  FOR  LENGTH 
OF  100  FEET,  ACCORDING  TO  A.  R.  WOLF 


Radiation. 

Radiation. 

Diam. 

2lbs. 

sit*. 

2lbs. 

S  Ibs. 

I 

36 

60 

4 

1920 

3200 

I* 

72 

1  20 

5 

3720 

6200 

I* 

120 

200 

6 

6000 

IOOOO 

2 

280 

480 

8 

12800 

21600 

2* 

528 

880 

10 

23200 

39000 

3 

QOO 

I5OO 

12 

37000 

62000 

14 

54000 

92000 

10 


For  any  other  length,  multiply  values  in  table  by  —j=.     For 
a  single  pipe  system  the  pipe  should  be  about  50  per  cent  larger 


DIRECT  STEAM  HEATING  139 

than  the  steam  pipe  for  a  double  pipe  system.    Never  use  a 
smaller  steam  main  than  ij  ins.  or  a  smaller  return  than  i  in. 

Another  method  is  to  determine  the  amount  of  steam  required 
for  a  given  amount  of  radiation,  and  after  finding  the  volume 
of  this  steam,  determine  the  area  of  the  pipe  to  give  a  definite 
velocity.  For  large  mains  of  8  ins.  or  over  6000  ft.  per  minute 
may  be  used,  while  for  smaller  mains  a  velocity  of  3000  ft.  per 
minute.  This  may  be  written  as  a  formula: 


-      ve 


,     . 


a  =  area  of  pipe  in  square  inches  ; 
A  =area  of  heating  surface  in  square  feet; 
h  =  transmission  constant  for  the  heating  surf  ace  in  B.t.u. 

per  square  foot  per  hour; 
s  =  volume  of  i  Ib.  of  steam  in  cubic  feet; 
#  =  heat  content  of  steam  in  B.t.u.  per  pound; 
£  =  heat  of  liquid  of  condensed  steam  in  B.t.u.  per  pound; 
Vel.  =  vel.  of  steam  in  feet  per  minute. 

In  determining  the  diameter  of  the  pipe,  the  table  of  actual 
areas  on  page  86  should  be  used  rather  than  solving  for  the 
diameter  of  the  circle  of  area  a. 

The  best  method  of  determining  the  area  of  pipe  to  carry 
a  given  quantity  of  steam  is  to  assume  the  allowable  drop  in 
pressure  in  the  given  length,  and  then  to  use  the  method  given 
in  the  Transactions  of  the  American  Society  of  Mechanical 
Engineers,  Vol.  XX,  p.  342,  by  R.  C.  Carpenter  and  E.  C.  Sickles. 
The  formula  derived  in  this  paper  is 


of  pressure  in  pounds  per  square  inch  in  length 
ofLft; 

K  =  constant  =  0.002  7  ; 
d'  =  diameter  of  pipe  in  inches; 

D  =  weight  of  i  cubic  foot  of  steam  at  given  pressure; 
W  =  weight  of  steam  in  pounds  per  minute. 


140          ELEMENTS  OF  HEATING  AND  VENTILATION 
This  may  be  written: 

/       3.6W'2Z, 
/>  =  0.000131 1  i +-^r  J£^5~> 

or 


(6s) 


In  this  the  value  of  dr  in  the  bracket  is  assumed  for  the  first 
approximation,  and  then  after  substitution  of  this  value  within 
the  radical  a  second  approximation  is  found.  The  table  given 
below  has  been  prepared  by  the  author  for  the  weight  of  steam 
at  5  Ibs.  gage  pressure  which  will  be  discharged  for  a  \  Ib.  drop 
in  the  length  given.  If  the  pressure  or  drop  is  different  from 
that  given,  the  weight  of  steam  at  a  pressure  of  5  Ibs.  and  a  drop 
of  \  Ib.  equivalent  to  the  actual  steam  is  given  by 


To  use  lengths  different  from  those  given  in  the  table, 
it  is  to  be  remembered  that  p  varies  as  L  and  Wf  varies  inversely 
as  VL- 

The  paper  of  Carpenter  and  Sickles  gives  the  loss  in  pressure 
in  one  globe  valve  to  be  equal  to  the  loss  in  700  diameters  of 
the  pipe,  while  an  elbow  gives  a  drop  in  pressure  equal  to  that 
from  520  diameters  of  pipe. 

To  show  the  application  of  the  table,  suppose  it  is  required 
to  deliver  240  Ibs.  of  steam  per  hour  at  10  Ibs.  gage  pressure 
through  a  pipe  45  ft.  long,  with  2  elbows  and  a  gate  valve  with 
a  drop  of  not  over  J  Ib. 

To  find  the  equivalent  steam  per  minute  at  5  Ibs.  pressure 
and  J  Ib.  drop,  the  formula  (66)  is  used  (D  =  0.0607  f°r  I0  Mbs. 
steam). 


2400.049X1 


DIRECT  STEAM  HEATING 


141 


FLOW  OF  STEAM  IN  POUNDS  PER  MIN.  AT  5  LBS.  GAGE  PRESSURE 
WITH  i-POUND  DROP 


Diam. 
in 
Inches 

Length  in  Feet 

25 

5° 

75 

100 

150 

200 

300 

500 

IOOO 

1 

4 

0-51 

0.36 

o.  29 

0.25 

O.2I 

0.18 

0.15 

O.  II 

0.08 

I 

I  .00 

0.72 

0.58 

0.51 

0.41 

0.36 

o.  29 

0.23 

0.16 

Ij 

2.46 

1.61 

!-3T 

1.14 

0-93 

0.81 

0.66 

0-51 

0.36 

i* 

3-°4 

2.05 

i-75 

1.52 

1.24 

1.07 

0.88 

0.68 

0.48 

2 

7.09 

5.02 

4.09 

3-54 

2.89 

2-51 

2.04 

i-59 

I  .12 

2| 

ii  .70 

8-33 

6-79 

5-89 

4.80 

4.  16 

3-39 

2.64 

1.86 

3 

21  .40 

15.10 

12.30 

ii  .40 

8.72 

7-56 

6.18 

4-78 

3-38 

4 

45.60 

32.20 

26  .  30 

22.80 

18.60 

16.  10 

13.10 

10.  10 

7.20 

5 

84.80 

60.00 

48.80 

42.40 

34.60 

30.00 

24.40 

19.00 

I3-40 

6 

138.00 

97.60 

79.60 

69.00 

56-30 

48.80 

39.80 

30.90 

21.80 

7 

2O2.OO 

144.00 

118.00 

IO2  .OO 

83.00 

72  .00 

58.80 

45.60 

32.20 

8 

29O.OO 

205  .00 

167.00 

145.00 

118.00 

103.00 

84.00 

65.00 

45-90 

10 

525-00 

371.00 

302  ..oo 

262  .OO 

214.00 

.224.00 

151.00 

117.00 

83.00 

12 

885.00 

627.00 

511.00 

443  •  oq 

362.00 

314.00 

256.00 

198.00 

140.00 

14 

I26o.OO 

891  .00 

726.00 

630  .  oo 

514.00 

445-oo 

364.00 

282.00 

199.00 

18 

2370.00 

1680.00 

1370.00 

1190.00 

993.00 

862.00 

704.00 

595-oo 

385-00 

24 

527O.OO 

3730.00 

3410.00 

2640  .  oo 

2  1  50  .  OO 

1860.00 

1520.00 

1180.00 

834.00 

Assume    as    first    approximation    that 
table  dr  =  2  ins. 


Then 


We  for  200  ft. 


50    ft.     Then  from 


df  from  table,  for  second  approximation  =  2  ins. 

This  pipe  will  be  of  sufficient  size. 

To  find  the  diameter  by  use  of  the  table  on  page  138  it  is 
necessary  to  change  pounds  of  steam  to  square  feet  of  heating 
surface.  Roughly  one  quarter  of  a  pound  of  steam  is  con- 
densed per  square  foot  of  surface  per  hour. 

7250  B.t.u.  per  square  foot\ 
\      1000  B.t.u.  per  pound     / 


240  Ibs.  of  steam  per  hour  will  be  consumed  by  960  sq.ft.  of 


142         ELEMENTS  OF  HEATING  AND  VENTILATION 

surface.     From  the  table  this  requires  a  3-111.  pipe  for  the  supply 
or  a  4-in.  pipe  for  a  single  pipe. 

Allowing  3000  ft.  per  minute  as  the  velocity,  the  following 
method  is  used  : 

240 
240  Ibs.  of  steam  per  hour  =  T~^  —  T~  =  65.9  cu.ft.  per  minute; 

65.0X144          , 
A=—  -=3.iosq.m. 

3000 

d'  =  2  ins. 

In  this  manner  the  size  of  the  supply  main  to  various  risers 
may  be  found.  The  pipe  is  reduced  at  various  points. 

To  find  the  size  of  the  return,  an  empirical  method  of  using 
one-quarter  of  the  area  of  the  supply  may  be  used  until  smaller 
sizes  than  3-in.  returns  are  found,  when  one-hajf  the  area  may 
be  used.  In  no  case  should  a  smaller  size  than  i  in.  be  used. 

As  another  method  the  volume  of  the  condensed  steam  may 
be  determined,  and  from  this  after  assuming  a  velocity  the  area 
may  be  found.  Chezy's  formula  may  be  used  to  find  v. 


.......     (67) 

where 
• 

c  =  coefficient  =  75  for  iron  pipe  about  4  ins.  in  diameter; 
v  =  velocity  in  feet  per  second; 

t.  A      r       A-      •    t  area  pipe  i 

r  =  hydraulic  radius  in  feet  =  —   —  ;  --  :  —    -  ;  —  =  —zd  ; 

wetted  perimeter  pipe     48 

d'  =  diameter  in  inches; 
s  =  slope  of  pipe  in  feet  per  foot  ; 
v  is  about  2  ft.  per  second. 

The  condensed  steam  is  accompanied  by  more  or  less  air,  so 
it  is  well  to  consider  only  one-half  of  the  pipe  as  carrying  water 
in  the  expression  above.  This  gives  the  same  hydraulic  radius. 
The  volume  of  water  is  much  greater  per  pound  at  high  tem- 
perature, and  this  must  be  considered  in  determining  the  area 


DIRECT  STEAM  HEATING 


143 


to  carry  a  given  volume.     The  table  below  will  be  of  assistance 
in  this  connection. 

WEIGHT  OF  WATER  AT  DIFFERENT  TEMPERATURES 
PER  CUBIC  FOOT 


Temp. 

100°  P. 

130°  F. 

160°  F. 

190°  F. 

212°  F. 

220°  F. 

Pounds  per  cubic  foot 

61  .9 

61.5    - 

61  .0 

60.4 

59-8 

59-4 

In  placing  steam  or  return  mains,  care  must  be  exercised 


Horizontal  Line 


FIG.  in. — Drip  Pots. 

to  run  the  pipes  with  a  decided  pitch  in  one  direction  or  the  other.  / 
It  is  best  where  possible  to  pitch  the  pipe  downward  in  the  direc- 
tion of  flow  at  least  i  in.  in  30  ft.  Where  this  is  not  possible, 
and  the  pipe  rises  in  the  direction  of  flow,  it  is  advisable  to 
install  drip  pots  at  intervals,  which  are  drained  as  shown  in  Fig. 
in.  This  enables  one  to  cut  down  the  amount  of  water  which 
is  flowing  back  against  the  steam  current,  and  being  in  condition 


144         ELEMENTS  OF  HEATING  AND  VENTILATION 

to  be  taken  up  by  the  steam  current  whenever  there  is  a  change 
in  the  demand  for  steam,  changing  the  relative  velocity  of  the 
steam  and  water.  The  endeavor  should  be  made  to  drain  in 
the  direction  of  flow,  but  where  this  would  lead  to  complications 
a  carefully  designed  line  with  the  drainage  in  the  opposite 
direction  will  give  satisfactory  results. 

The  branches  should  be  arranged  to  care  for  condensation. 
The  branches  to  returns  or  drips  should  enter  the  tops  of  mains. 
In  power  plant  work  it  is  customary  to  take  the  branches  from 
the  top  of  the  main  to  insure  drier  steam.  The  branches  from 
the  main  in  heating  systems  should  be  taken  from  the  top  when 
the  line  is  at  the  bottom  of  the  riser,  but  in  the  Mills'  system 
it  is  better  to  take  it  from  the  bottom  of  the  pipe,  thus  dripping 
the  main  at  each  branch.  An  examination  of  Figs.  99,  100,  101 
will  show  these  arrangements. 

Care  must  be  exercised  to  have  no  portion  of  a  main  below 
the  extensions  from  each  end  of  it  so  that* condensation  will 
collect  in  this  part  and  stop  the  flow.  Such  pockets  may 
prevent  the  circulation  of  steam  in  a  low  pressure  system 
and  in  any  case  they  may  produce  water  hammer.  Pockets 
if  necessary  in  any  part  of  the  system  must  be  drained. 
With  a  vacuum  system  small  pockets  may  be  cared  for  auto- 
matically by  the  pump,  causing  sufficient  vacuum  to  lift  the 
water. 

Valves  are  to  be  placed  at  high  points  in  the  line,  globe 
valves  being  placed  with  the  valve  stems  horizontal,  while  with 
gate  valves  the  stems  are  vertical  and  the  handle  is  placed 
above.  These  two  positions  prevent  the  water  from  collecting 
behind  the  valve. 

To  prevent  the  formation  of  a  pocket  when  there  is  a  reduc- 
tion of  diameter  the  regular  reducer  at  A,  Fig.  112,  is  replaced 
by  an  offset  reducer  J5,  or  by  on  eccentric  tee  C,  Fig.  112. 

The  risers  may  be  run  exposed  in  the  various  rooms  or  they 
may  be  concealed  in  chases  behind  the  plaster.  The  former 
method  is  advisable,  as  repairs  may  be  easily  made.  For  high- 
class  work  where  pipes  would  be  unsightly  the  latter  method 
is  used.  In  this  case  the  pipes  and  fittings  should  be  care- 


DIRECT  STEAM  HEATING 


145 


fully  selected  and  the  pipes  should  be  tested  before  the  plaster 
is  put  on. 

The  radiator  connections  are  best  carried  beneath  the  ceiling 
in  the  room  below,  although  in  concealed  work  they  are  carried 
in  the  space  between  floor  and  ceiling  or  directly  under  the  floor. 
Concealed  work  is  undoubtedly  the  more  attractive,  but  when 
trouble  is  experienced  there  must  be  considerable  cutting  before 
repairs  can  be  made. 

In  many  systems  the  air  valves  are  connected  to  an  air  line 


n 


f 

1 

FIG.  112. — Regular  and  Offset  or  Eccentric  Reducers. 

which  discharges  some  place  in  the  basement,  as  shown. 
113.  The  purpose  of  this  was  originally  to  deliver  any 
of  water  into  the  sewer  and  not  on  the  floor  of  the  room.  Lately 
it  has  been  used^in  the  Paul  system  for  the  attachment  of  a 
vacuum  air  pump  to  draw  the  air  from  the  radiators,  thus  reduc- 
ing back  pressure  in  a  single  pipe  system.  The  objection  to 
an  air  line  is  the  fact  that  an  improperly  set  air  valve  may 


in  Fig.;      / 
iy  drip  I  V 
Lately  1 


146        ELEMENTS  OF  HEATING  AND  VENTILATION 

deliver  steam  through  this,  thus  interfering  with  the  action 
of  other  valves  and  wasting  steam  unless  the  discharge  end  of 
the  line  is  brought  to  a  point  where  the  attendant  is  sure  to 
observe  it. 

Pipe  covering  is  used  on  pipes  which  are  put  in  chases  or 
are  carried  through  spaces  which  are  to  be  kept  cool.  The 
materials  used  are  to  be  good  non-conductors  and  substances 


FIG.  113. — Air  Line. 

which  will  not  burn  or  char.  The  substances  used  are  85  per  cent 
magnesia,  asbestos,  hair  felt,  mineral  wool  and  cork.  The  heat 
loss  is  found  as  for  any  conductor  by  the  formula  H  =KA  (ts  —  /<,). 
Tests  have  been  made  by  a  number  of  persons  to  determine  the 
values  of  these  as  heat  insulators,  and  the  results  are  similar. 
The  table  below  gives  the  results  of  Geo.  H.  Barrus  as 
reported  in  the  Transactions  of  the  Society  of  Mechanical 
Engineers. 


DIRECT  STEAM  HEATING  147 

LOSS    OF    HEAT    PER    SQUARE    FOOT     OF    PIPE     SURFACE    PER 
DEGREE  DIFFERENCE  IN  TEMPERATURE  PER  HOUR  IN  B.T.U. 

io-in.  pipe,  150  Ibs.  steam  pressure. 

Asbestos  sponge  felt,  76  laminations,  .(if")  0.280 

M         "66         "            ..(i&")  0.306 

Magnesia,  i^  ins.  thick 0.354 

Asbestos  navy  brand (if")  0-387 

Watson's   Imperial,    i    in.    thick    (asbestos 

paper) o .  428 

(Nonpareil  cork o. 290) 

Bare  pipe 3 . 220 

2  ins.  pipe,  80  Ibs.  pressure. 

Asbestocel  i  in.  thick o.  728 

New  York  air  cell o.  750 

Carey's  moulded  i  in o .  768 

Asbesto  sponge  molded  i  in o.  778 

Cast's  air  cell  i  in.  thick o.  793 

(Nonpareil  cork 0.512) 

Watson's  Imperial o. 548 

These  were  reduced  to  same  thickness  of  i  in.,  and  gave  the 
following  results: 

10  in. — 150  Ibs. 
Asbesto  sponge,   66  laminations 0.341 

";     76      ((        0.342 

Magnesia o .  394 

Watson  imperial o .  428 

Asbestos  navy  board o .  472 

2  ins. — 150  Ibs. 
Asbestos  sponge  hair  felt,  3  ply 0.497 

"       "       2    "" 0.527 

Asbestos  sponge  felt,  59  laminations o.  527 

"48  0.531 

Magnesia o .  53 1 

Asbestos  navy  brand 0.652 


148         ELEMENTS  OF  HEATING  AND  VENTILATION 

These  coverings  save  about  80  to  90  per  cent  of  the  heat  which 
would  be  radiated  from  the  bare  pipe.  The  covering  will  save 
its  cost  in  less  than  half  a  year  with  steam  at  about  100  Ibs. 
pressure.  The  kind  of  covering  is  an  important  item,  as  in  many 
cases  the  more  expensive  covering  will  save  much  more  than 
its  original  cost. 

The  coverings  are  usually  prepared  in  sectional  form  and 
applied  to  the  pipes  in  sections  with  canvas  covers,  as  shown 
in  Fig.  114,  one  section  being  an  air  cell  covering,  the  other  a 
solid  covering.  Each  section  is  banded  by  at  least  two  bands. 
At  times  blocks  of  covering  are  applied  which  are  wire  banded 


FIG.  114. — Pipe  Covering. 

and  then  a  hard  plaster  is  applied  to  the  surface,  making  a 
good  finish. 

The  covering  costs  about  twenty  to  forty  cents  per  square 
foot  of  pipe  surface,  depending  on  the  diameter  of  the  pipe, 
the  smaller  pipe  costing  more  per  square  foot  and  will  save  from 
90  cents  to  140  cents  per  year  of  8760  hours  with  coal  at  $4.00 
per  long  ton. 

Using  the  tables  of  Chapter  V,  the  various  radiators  for  the 
rooms  are  found,  and  their  positions  determined  from  the  plans 
and  placed  on  the  development  of  Fig.  105.  After  this  is  done 
the  sizes  of  risers  are  determined  by  making  the  table  as  shown 
below,  and  then  the  sizes  are  marked  on  plans  and  develop- 
ment. The  size  of  the  supply  is  next  found  and  marked  on 
the  plans. 


DIRECT  STEAM  HEATING 


149 


RESIDENCE  OF  L.  Q.  SMITH 


Riser. 

A. 

B. 

C. 

D. 

E. 

Radiators  

la.     52 
70.     48 

IOO 

ib.     52 
76.     48 

IOO 

20.       36 

8a.     48 

84 

26.      36 
36 

3<*.  nf 
ga.  i6| 

28^ 

Size. 

if 

l| 

i| 

ij 

ii- 

Riser. 

F. 

G. 

H. 

/. 

y. 

Radiators  

4d.     42! 
ioa.     20 

62f 

IO&.    2O 
.    20 

$a-  32 

Iltf.    20 
52 

5*-  32 
nb.  20 

52 

6a.  75 

120.    14 
89 

Size. 

if 

I 

Ti 

ii 

jl 

A  table  is  now  made  to  insert  in  the  specifications,  giving 
information  to  the  contractor  in  regard  to  the  kind,  size,  and 
location  of  radiators.  » 


FIRST  FLOOR 


Room. 

Radiator. 

Heating 
Surface. 

Temp. 

Ratio. 

I 

i  a.  2  Column  Peerless,  38  ins. 

52 

ib.                                     38   " 

52      104 

70°  F. 

30 

2 

2a.                   "                38   " 

36 

2b.                             "                        38     " 

36        72 

70°  F. 

30 

3 

3«-                    "                23   " 

"I 

70°  F. 

36 

4 

40.                                       26    " 

42f 

70°  F. 

32 

5 

50.                                     20   " 

32 

56.                    "                20   " 

32        64 

70°  F. 

26 

6 

6a.                   "               45   " 

75 

70°  F. 

30 

150         ELEMENTS   OF  HEATING  AND  VENTILATION 

SECOND  FLOOR 


Room. 

Radiator. 

Heating 
Surface. 

Temp. 

Ratio. 

7 

70. 

2  Column  Peerless,  26  ins. 

48 

7b. 

<  <                      <  < 

48 

96 

70°  F. 

30 

8 

go. 

38   " 

48 

70°  F. 

4i 

9 

ga. 

32    ' 

i6f 

70°  F. 

45 

10 

ioa. 

"                       20    " 

20 

106. 

20     " 

20 

40 

70°  F. 

42 

ii 

ua. 

20     " 

20 

nb. 

"                       20     " 

2O 

40 

70°  F. 

42 

12 

I2d. 

"                       2O     '' 

U 

70°  F. 

34 

1  1       P 

Q^» 

^\  l^V    '',''Ji  ii.}!1                  '  i  1      '  ' 

xNh  *— 

N>    *"* 

• 
L 

T^     u," 

UT 

S— 

—i  —  —  t*^  

4L  j  Risers  y^Bt  /  Risers           l"        Risers/,,}  J 

o  Risers    **" 
ZX" 

l 

1  ' 

-i>?-H 

" 

(f== 

n 

1 

4_J 

5  Sec.-,22"Heater 

•\\/'< 

2" 

S     t>  Risers' 

\ 

it 
< 

c  Risers 

i 

2" 

n  ji> 

=/  '  ^ 

n/i 

s^ 

^>v  ns»  Risers  g  ^ 

\ 

t1     1            7     1"  ~"                  1  !1. 

dbiJ  d  Risers 

fi    pR^ers          ^                         p-^,isers/'t.UL-J^ 

FIG.  115. — Cellar  Plan  of  House  for  Dir  ect  Heating. 

With  the  table  in  the  specifications  and  the  development 
there  is  no  ambiguity  or  chance  for  questions  to  arise  in  the 
completion  of  the  work.  Each  bidder  knows  what  is  wanted. 
At  this  point  it  is  well  to  call  attention  to  the  fact  that  the  heat- 
ing engineer  should  know  that  what  he  has  designed  is  sufficient 


DIRECT  STEAM  HEATING 


151 


152         ELEMENTS  OF  HEATING  AND  VENTILATION. 

for  the  work  and  not  to  try  to  shift  responsibility  by  placing 
a  clause  in  the  specification  that  the  contractor  has  to  guarantee 
to  heat  the  building  to  70°  in  zero  weather.  If  this  is  not  accom- 
plished after  specifying  the  amount  of  radiation  it  is  clearly 
the  fault  of  the  engineer  and  not  of  the  contractor,  and  the 
engineer  should  assume  the  responsibility. 

The  cellar  plan  in  Fig.  115  gives  the  arrangement  of  supply 
and  return  pipes  in  the  cellar  with  the  position  of  the  boiler 
and  flue. 

Fig.  116  illustrates  a  development  of  a  larger  bmlding,  show- 
ing the  method  used  to  fix  the  sizes  of  risers  and  mains. 


CHAPTER  VII 
HOT-WATER  HEATING 

IN  hot-water  heating  there  are  several  methods  of  arranging 
the  pipes.  In  one  system  there  is  a  single-flow  pipe  or  main, 
Fig.  117,  in  the  basement  from  which  supply  and  return  risers 
are  run  to  the  different  radiators.  The  flow  pipe  leaves  the 


FIG.  117. — Hot  Water  with  Single  Main. 

top  of  the  water  boiler  and  re-enters  at  the  bottom  after  making 
its  completed  circuit.  The  radiators  used  in  hot-water  instal- 
lations are  usually  made  with  the  sections  connected  together 
at  top  and  bottom  as  was  mentioned  on  page  75,  where  the  hot- 
water  form  of  radiator  was  shown  in  Fig.  46.  In  a  single-flow 
pipe  system  the  water  is  gradually  cooled  as  it  passes  through 

153 


154 


ELEMENTS  OF  HEATING  AND  VENTILATION 


the  pipes  owing  to  the  cool  return  water  being  added.  To  aid 
the  circulation  and  to  keep  the  cold  water  from  mixing  too 
rapidly  with  the  warm  water,  the  branches  to  the  supply  risers 
are  taken  off  from  the  top  of  the  pipe,  while  the  return  is  con- 
nected to  the  bottom  of  the  pipe.  For  this  purpose  special 
tees  are  made  and  installed  as  shown  in  Fig.  118.  The  supply, 
being  taken  from  the  top  of  the  flow  pipe  first  and  then  the 


Sugply 


o 


Return. 
FIG.  118. — Eccentric  or  Offset  Tees  for  Hot  Water  Main. 


FIG.  IIQ.  — Flow  Line  Using  Y's. 


Of 


using 


return  from  the  bottom.     Fig.    119  shows  a  method 
Y's  to  accomplish  a  more  positive  circulation. 

The  separate  supply  flow  pipe  and  return  flow  pipe  are  shown 
in  Fig.  1 20.  In  this  the  two  pipes  both  rise  as  they  leave  the 
boiler,  the  supply  from  the  high  part  of  the  boiler  and  the  return, 
through  a  vertical  leg  from  the  bottom  of  the  boiler.  In  this 
case  there  is  no  danger  of  getting  the  currents  mixed  and  the 
branches  may  be  taken  from  any  part  of  the  lines.  In  the  figure 


HOT-WATER  HEATING 


155 


the  risers  which  are  connected  to  the  part  of  the  supply  near 
the  boiler  are  at  the  far  end  of  the  return  flow  line.     In -this 


FIG.  120.— Two-pipe  Hot  Water  Systei 


Fig.  121. — Branch  Connections. 

way  the  length  of  the  various  circuits  may  be  equalized.  Fig. 
121  shows  one  method  of  taking  off  branches  from  the  flow  lines 
when  they  are  placed  side  by  side,  and  there  is  not  sufficient 


156 


ELEMENTS  OF  HEATING  AND  VENTILATION 


room  beneath  the  joists  to  have  one  branch  cross  the  flow  pipe 
and  to  use  an  elbow  on  a  tee  pointing  straight  up  with  a  close 
nipple. 

One  fitting  may  be  used  as  shown  in  Fig.  122  if  the  tee  is 


FIG.  122. — Branch  Connections. 

turned  with  the  branch  at  45°  to  the  horizontal  instead  of  in 
the  horizontal  position.  In  many  cases  there  is  not  sufficient 
room  to  turn  the  tee  vertically  as  shown  in  Fig.  123,  and  the 
methods  of  Figs.  121  and  122  are  resorted  to.  This  applies 
equally  well  to  all  forms  of  piping  work  for  steam  or  water. 


FIG.  123. — Branch  Connections. 

The  branch  is  sometimes  taken  below  the  flow  line  as  shown 
in  Fig.  124,  when  it  is  desired  to  have  sluggish  action,  although 
air  may  collect  in  such  a  branch.  The  Honeywell  Company 
advise  the  use  of  connections  of  Fig.  121,  where  a  reduction 


HOT-WATER  HEATING 


157 


occurs  in  the  size  of  the  main,  using  only  a  branch  to  a  first-floor 
radiator.  They  never  connect  a  high  riser  branch  at  such  a 
point,  as  the  circulation  in  such  a  riser  at  a  reduction  of  section 
might  cause  excessive  circulation  in  the  section  supplied  by 
the  riser.  They  recommend  connections  as  shown  in  Fig.  124 
for  all  branches  near  boilers  so  as  to  cut  down  circulation  at 
these  points.  Drips  must  be  provided  for  draining  the  pockets 
formed  in  this  branch  when  the  system  is  being  drained.  If 
this  is  objectionable  the  branch  shown  in  Fig.  121  may  be  used. 
In  any  case  the  endeavor  must  be  made  to  have  the  circulation 
good  in  all  radiators. 

The  complete  circuit  system,  Fig.  101,  may  be  used  for  hot 


To  Radiator 


Rises 


U 


FIG.  124. — Branch  Connection. 


FIG.  125. — Riser. 


water  as  well  as  steam.  In  this  the  supply-flow  pipe  at  the  top 
of  the  building  is  fed  from  the  top  of  the  boiler  through  a  riser 
and  the  return-flow  pipe  is  placed  at  the  bottom  of  the  building. 
Of  course  in  this  case  there  are  supply  risers  connected  to  the 
top  of  the  radiators  on  one  side  while  the  return  risers  are  con- 
nected to  the  lower  part  of  the  other  side  of  the  radiator. 

The  risers  are  connected  to  the  branches  and  in  most  hot- 
water  installations  there  are  no  control  valves  on  the  branches 
to  risers. 

If  there  are  a  number  of  radiators  on  a  riser  there  is  some 
danger  of  the  circulation  being  established  in  the  riser  to  an  upper 
radiator  and  thus  prevent  a  proper  supply  from  reaching  the  lower 
radiators.  There  are  several  methods  of  avoiding  this.  One 
method,  Fig.  125,  is  to  place  the  supply  to  the  radiator  at  the 


158         ELEMENTS  OF  HEATING  AND  VENTILATION 

end  of  a  section  of  the  riser  and  continue  the  riser  by  means  of 
a  tee  and  an  elbow.  In  this  way  there  is  resistance  to  upward 
flow  due  to  the  breaking  of  the  direct  path.  In  Fig.  125,  if  the 
radiator  is  assumed  to  the  right  and  the  continuation  of  the  riser 
is  assumed  to  the  left  the  same  result  is  accomplished.  A  third 
method  is  to  reduce  the  riser  diameter  at  the  place  where  a  con- 
nection is  taken  off  to  a  radiator,  the  constriction  throwing  more 
resistance  on  the  flow  and  thereby  giving  the  lower  radiator  a 
supply  of  water.  Fig.  125  shows  the  radiator  connection  lead- 
ing at  right  angles  from  the  riser  without  a  swing  ell.  This 
can  be  done  in  the  case  of  hot-water  work  if  the  lines  are  not 


FIG.  126. — O.  S.  Connector. 

too  long.  The  table  in  Chapter  VI  gives  the  expansion  of  180° 
heating  to  be  less  than  i  in.  to  100  ft. 

One  of  the  best  methods  of  causing  water  to  flow  into  a  lower 
radiator  is  to  use  the  O.  S.  distributors,  Fig.  126.  These  are 
special  tees  with  a  deflecting  partition  and  in  most  cases  a  reduc- 
tion in  size  of  piping  on  the  run. 

When  necessary  to  hug  the  wall  of  a  building  the  branch  may 
be  taken  off  at  an  angle  to  the  wall  instead  of  parallel  to  it  and 
by  the  use  of  a  45°  ell,  as  shown  in  Fig.  127,  the  line  is  brought 
parallel  to  the  wall. 

To  find  the  amount  of  radiation  for  a  hot-water  system,  the 
same  method  is  used  as  for  the  steam  system.  The  amount 
of  heat  for  a  given  room  from  Chapter  V  is  divided  by  the  amount 


HOT-WATER  HEATING 


159 


of  heat  transmitted  per  square  foot  of  radiation  for  hot  water 
and  the  result  will  give  the  amount  of  radiation.  This  number 
is  about  170  B.t.u.  per  square 


Wall 


foot  per  hour.     Another  result     ^  waii 

which  is  worth  remembering 
is  that  i  sq.ft.  of  hot  water 
radiation  requires  i  gallon  of 
water  or  about  |  of  a  cubic 
foot  or  8  Ibs.  of  water  per 
hour,  as  the  drop  in  tempera- 
ture is  about  20°  F. 

After  the  amount  of  radia- 
tion is  computed  it  is  placed 
on  plans  and  developments  as 
in  Chapter  VI  and  then  the  pipe  sizes  are  found.  To  check  the 
results  of  the  amount  of  heating  surface  the  following  table 
is  given: 


FIG.  127. — Radiator  Connection. 


ESTIMATED    CUBIC    FEET    OF    VOLUME   HEATED    BY 
FOOT    OF    HOT-WATER    HEATING    SURFACE 


SQUARE 


Residences : 

Living  rooms 20  to  40 

Sleeping  rooms 30  to  50 

Offices 30  to  50 

Schools 25  to  50 

Factories 40  to  80 

Assembly  halls 45  to  90 

Hotels 50  to  70 

Stores 50  to  70 

Churches 80  to  1 20 

Auditoriums 80  to  120 

Gymnasiums 1 20 

Workshops 130 

The  size  of  the  pipes  in  hot-water  systems  depends  on  the 
velocity  of  the  water  and  the  amount  of  water  to  be  carried. 
The  velocity  depends  on  the  height  of  the  various  radiators 


160         ELEMENTS  OF  HEATING  AND  VENTILATION 

and  the  difference  in  the  weight  of  the  water  on  the  hot  side  and 
the  cold  side. 

Suppose  the  height  of  a  radiator  from  the  return-flow  pipe 
line  is  L  ft.  and  the  temperature  of  the  supply  is  ts  and  that  of 
the  discharge  is  td.  These  are  often  about  180°  and  160°  respect- 
ively. Let  the  corresponding  weights  per  cubic  foot  be  D8 
and  Dd.  The  weight  of  water  in  the  supply  column  is  LADS 
and  in  the  return  is  LADd  and  that  in  the  flow  mains  is 

L'A'(  --  •].    A'  is  the  area  of  the  pipes  in  square  feet  and 

L'  is  the  length  of  each  of  the  flow  mains.  The  force  in  pounds 
causing  flow  is  LADd  —  LADs.  This  is  reduced  to  feet  head 
by  dividing  by 

A(DA+D,) 


or 


If  now  this  value  for  h  be  inserted  in  the  formula 


where 

v  =  velocity  in  feet  per  second; 
/j  =  head  in  feet  causing  flow; 
g  =  32.2=  acceleration  of  gravity; 
/*=  friction  factor  =  0.02  ; 
/  =  total  length  of  system  ; 
d  =  diameter  of  pipe  (mean)  ; 
n  =  number  of  bends; 
m  =  friction  factor  for  i  bend  =  J, 

the  velocity  to  be  expected  may  be  found.  In  this  there 
will  be  varying  velocities  in  the  various  risers  so  that  in  general 
an  empirical  table  is  used  for  the  various  risers  after  the  amount 
of  radiation  is  known.  From  the  amount  of  radiation  the  amount 


HOT-WATER  HEATING  161 

of  water  needed  per  hour  may  be  found  by  the  rules  given  above 
or  to  be  exact  the  weight  of  water  may  be  computed  thus : 

w=  H 


qs-qa 


W 
vols=— (71) 

vold  =  ^- (72) 

W= weight  of  water  per  hour  in  pounds; 
ZT  =  heat  to  be  given  off  per  hour; 
q  =  heat  of  liquid  at  supply  or  return. 

Knowing  the  volume,  the  area  of  the  pipe  is  given  by 

vol 
A  =  — (73) 

v 

For  use  in  computing  problems,  the  following  table  is  given. 

DENSITY  OF  WATER  AT  VARIOUS  TEMPERATURES 

Temperature 50  68                86               104              122 

Rel.  density 1.00025  1.000174  1.00425  1.0077  1.0119 

Temperature 140  158               176               194               212 

Rel.  density 1.0169  1.0226  1.0289  I-°357  1-0431 

To  apply  the  above  to  a  given  problem  suppose  7500  B.t.u.'s 
are  to  be  transmitted  from  radiators  per  hour  in  rooms  10 
20  and  30  ft.  from  basement  floor,  at  which  level  the  return 
water  enters  the  boiler.  The  hot  water  is  assumed  at  180° 
and  the  return  at  160°  F.  The  radiators  are  arranged  on  5 
risers.  The  flow  pipes  are  40  ft.  long. 

i st.  Heating  surface  approximate: 

75000 
^"=440, 

or  88  sq.ft.  per  riser. 


162  ELEMENTS  OF  HEATING  AND  VENTILATION 

2d.  Water  per  riser: 


V°L  =  1.03X62.5  =  "' 
3d.  Velocities  to  different  floors: 


I.030+I.023 


0.136  ft.; 
0.204  ft.; 


2X32.2X0.068  _ 

i>i=      ( — , r~    — =0.66  ft.  per  sec.; 


fl2  =  o.89  ft.  per  sec. 
VB=I  .03  ft.  per  sec. 

These  velocities  in  ft.  per  min.  are  respectively:  39.6,  53.4, 
61.8. 

The  velocities  will  practically  increase  with  the  square 
root  of  the  height. 

4th.  Areas  of  pipes: 

Using  mean  velocity  of  0.9  from  z>2,  the  following  results: 

r      •  -1  H.7XI44 

Area  of  riser  in  square  inches  =  — ——z —  =.52  sq.m. 

0.9X3600 

This  gives  a  f-in.  pipe  in  which  the  resistance  is  much  greater 
than  in  a  2-in.  pipe  used  in  computing  V.  Hence  a  recalculation 
should  be  made  giving  a  large  pipe. 

This  method  is  not  used,  as  it  is  lengthy  and  instead  a  table 
such  as  that  given  below  is  employed  generally. 


HOT-WATER  HEATING 


163 


SIZE  OF  PIPES  FOR  HOT-WATER  MAINS  AND  RISERS 


Mean  Height  of  Radiators. 


Radiation. 

10 

20 

30 

40 

50 

i   in< 

:h 

i    in 

ch 

in 

ch 

inc 

h 

IOO 

ij 

i 

150 

l| 

ii 

i 

200 

2 

i£ 

. 

i 

4 

1 

250 

2 

1  2 

I 

i 

4 

300 

2 

2 

1 

.  ] 

[| 

4OO 

2I 

2 

2 

2 

450 

2* 

2* 

2 

2 

500 

3 

2* 

2 

2 

IOOO 

4 

3 

5 

5 

Using  the  table  the  problem  above  would  require  a  i-in. 
pipe  for  88  sq.ft.  for  a  mean  head  of  20  ft. 

The  flow  lines  are  found  for  the  total  amount  of  radiation 
or  water. 

The  Honeywell  Company  determine  sizes  of  risers  and  flow 
pipes  by  adding  together  the  areas  of  valve  openings  or  areas 
of  radiator  connections  used  on  any  riser  or  supplied  by  the  flow 
pipe.  Their  valve  sizes  or  drilling  sizes  are  smaller  than  those 
recommended  by  others,  as  seen  by  comparing  tables  on  pages 
163  and  1 68.  Thus  in  the  problem  above  they  would  use  a 
f-in.  riser. 

The  connections  to  the  radiators  are  fixed  by  the  drilling  table 
of  the  radiator  manufacturers  as  given  in  Chapter  VI.  The 
drillings  for  the  water  radiator  are  repeated. 

SIZE  OF  OUTLETS  FROM  RADIATORS 


Sq.  Ft.  of  Radiation. 


Supply  and  Return. 


40 
40-72 

72 


i   Xi 


Air  valve  vent  tapping  ^  in. 

Although  the  best  circulation  is  obtained  when  two  valves 
are  used  on  hot- water  radiators,  a  single  valve,  Fig.  128,  may 
be  used.  This  is  known  as  the  Honeywell  unique  valve. 


164         ELEMENTS  OF  HEATING  AND  VENTILATION 

The  supply  goes  in  one  side  of  the  valve  and  enters  the 
radiator,  being  kept  from  short  circuiting  to  the  return  by  the 
partition  which  extends  into  the  radiator.  This  permits  the 
water  to  rise  through  the  first  section  of  the  radiator  and  fall 
through  the  remaining  sections.  The  handle  moves  a  diaphragm 
which  separates  the  two  elbow  openings  in  the  valve,  causing 
the  water  to  pass  in  on  one  side  of  the  partition  and  out  of  the 
other.  A  turn  of  one-sixth  of  a  revolution  causes  the  diaphragm 


ooooooooo  o  tfoo  o  o  ooooc 


FIG.  128. — Honeywell  Valve. 


FIG.  129. — Expansion  Tank. 


to  cut  out  the  opening  to  the  radiator  and  connect  the  two 
elbows,  by-passing  the  radiator. 

In  this  way  the  circulation  through  the  supply  and  return  is 
never  interfered  with.  This  valve  can  be  used  with  the  complete- 
circuit  system,  the  supply  elbow  being  turned  up  and  the  return 
down.  There  are  several  advantages  in  having  the  connections 
at  one  end;  the  radiator  may  be  enlarged;  the  cutting  is  at 
one  place  and  the  two  risers  may  be  kept  close  together. 

Since  water  expands  about  3  per  cent  in  being  heated  to 
1 80°  F.  it  is  evident  that  there  must  be  some  provision  to  care 


HOT-WATER  HEATING 


165 


for  this  expansion,  and  hence  all  hot-water  systems  are  provided 
with  an  expansion  tank,  Fig.  129,  or  its  equivalent.  The 
expansion  tank  is  connected  to  a  riser  A  at  the  highest  part  of 
the  system  and  is  provided  with  a  water  gage  to  show  the  level 
of  the  water  and  a  vented  overflow  B  leading  to  the  sewer. 

This  tank  should  be  of  such  a  volume  that  the  expansion 
of  cold  water,  say  at  70°  F.,  to  the  higher  temperature,  say  of 
200°  F.,  will  cause  the  water  to  rise  from  near  the  bottom  of 
the  tank  to  the  top  of  the  tank  or  to  the  top  of  the  water  column. 
The  size  should  be  such  that  the  latter  is  true,  then  at  all  times 
the  level  of  water  is  shown.  If  the  water  level  cannot  be  seen 


B"  A 

FIG.  130. — Expansion  Tank  with  Float. 

the  small  cock  at  the  bottom  of  the  gage  may  be  opened  to  indi- 
cate whether  water  is  present  or  not.  When  water  is  low  in 
the  tank  the  water  is  usually  fed  into  the  system  from  the  city 
supply,  which  is  connected  where  the  return  water  enters  the 
boiler. 

Another  method  to  ensure  the  system  being  kept  full  of  water 
is  to  have  a  tank,  Fig.  130,  with  a  ball  float  attached  to  the  high 
part  of  the  line.  Then  as  the  water  rises  it  is  carried  off  by  the 
overflow  A,  while  if  the  water  contracts  more  water  is  fed  into 
into  the  system  from  the  tank  through  B,  the  ball  float  control- 
ling the  admission  as  the  level  falls. 

These  tanks  are  placed  at  a  high  part  of  the  system,  but  it 
should  always  be  in  a  warmed  room,  so  that  there  is  no  danger 


166         ELEMENTS  OF  HEATING  AND  VENTILATION 


of  the  expansion  tank  freezing.  The  freezing  of  the  tank  would 
not  only  endanger  the  tank,  but  it  will  prevent  expansion  of 
the  water  as  it  is  heated,  thus  bringing  undue  strains  on  the  sys- 
tem and  rupturing  radiators  or  boiler. 

If  a  water  closet  is  on  the  top  floor  of  a  building,  the  water 
tank  of  the  closet  may  be  used  as  an  expansion  tank,  as  this  will 
always  have  water  over  the  bottom  of  the  tank. 

The  size  of  the  tank  may  be  found  by  computing  the  water 
content  of  the  system  and  then  using  3  per  cent  of  its  volume 
as  the  volume  of  the  tank.  In  general,  however,  the  tank  may 
be  proportioned  by  the  amount  of  radiating  surface  by  the  table 
below: 

EXPANSION  TANKS 


Size. 

Gallons 
Capacity. 

Sq.  Ft.  of 
Radiation. 

J 
Size. 

Gallons 
Capacity. 

Sq.  Ft.  of 
Radiation. 

10X20 

8 

250 

16X36 

32 

1300 

12X20 

10 

300 

16X48 

42 

2000 

12X30 

15 

500 

18X60 

66 

3000 

14X30 

20 

700 

20X60 

82 

5000 

16X30 

26 

950 

22X60 

100 

6000 

The  maximum  temperature  carried  on  a  hot-water  system 
is  fixed  by  the  height  of  water  carried  on  the  boiler.  Thus  if 
the  level  of  the  expansion  tank  is  about  40  ft.  the  water  at  the 
boiler  could  be  250°  F.  before  it  could  boil,  due  to  the  pressure 
on  it,  but  as  soon  as  this  heated  water  had  reached  a  higher 
level,  part  of  it  would  turn  into  steam  and  drive  the  water  out  of 
the  expansoin  tank.  In  most  cases  when  the  water  gets  beyond 
220°  F.  there  is  danger  of  driving  the  water  out  of  the  system. 

To  enable  one  to  carry  a  higher  temperature  in  very  cold 
weather  the  Honeywell  Generator,  Fig.  131,  is  used.  The  point 
A  is  connected  to  the  heating  system,  preferably  near  the  boiler. 
As  the  water  in  the  system  is  heated  it  expands  into  the  chamber 
B  driving  the  mercury  C  into  the  circulating  tube  D  and  the 
standpipe  E.  By  the  time  the  mercury  reaches  the  top  of  the 
circulating  pipe  the  lower  end  is  open  to  the  water  and  this 
rises  through  the  mercury,  causing  an  upward  flow,  the  mercury 


HOT-WATER  HEATING 


167 


which  is   discharged  into   the   separating    chamber  F   falling 
back  through  the  standpipe  E.     If  the  discharge  is  at  all  violent, 
the  baffle  plate  G  will  deflect  the  mercury  downward.     The  water 
then  passes  through  H  to  the 
expansion  tank. 

When  the  system  cools 
off  the  contraction  of  the 
water  causes  the  mercury  to 
be  forced  up  in  5,  allowing 
water  to  flow  back  through 
H  and  E  and  passing  up 
through  B  it  separates  from 
the  mercury  and  leaves  at  A . 

By  this  arrangement  it  is 
seen  that  the  water  in  A 
and  B  may  be  under  at  least 
a  pressure  produced  by  a 
column  of  mercury  equal  to 
the  height  of  the  circulating 
tube.  This'  usually  amounts 
to  about  10  Ibs.  per  square 
inch.  In  this  way  the  press- 
ure on  the  water  in  the 
system  may  amount  to  10 
Ibs.,  permitting  the  tempera- 
ture to  reach  about  240°  F. 

The  Honeywell  Company 
claims  that  this  device  will 
accelerate  the  flow  of  water 
through  the  system  even 
under  low  temperatures. 
This  device  does  not  increase 
the  driving  force  unless  the  - 

FIG.  131. — Honeywell  Generator. 

temperature  is  increased,  as 

the  system  is  closed,  there  being  the  same  static  difference  of 
pressure  throughout  the  system  due  to  temperature  difference, 
but  in  case  of  need  the  possibility  of  getting  a  higher  tem- 


168          ELEMENTS  OF  HEATING  AND  VENTILATION 

perature  on  one  side  means  that  there  can  be  more  difference 
between  the  weights  of  the  water  in  the  ascending  riser  and  in 
the  return  riser,  and  hence  there  may  be  a  more  rapid  circula- 
tion. The  generator  is  a  very  ingenious  and  valuable  device 
for  increasing  the  temperature  of  the  water  and  thus  the  value 
of  each  square  foot  of  radiation,  and  at  the  same  time  increasing 
the  unbalanced  pressure  due  to  the  difference  in  density  of  the 
hotter  water,  so  that  smaller  pipe  may  be  used.  It  will  do  this 
with  safety. 

The  drillings  recommended  by  this  company  for  radiators 
are  as  follows: 

FIRST  FLOOR 

Up  to  30  sq.ft |  inch 

30  to  75    "    J    " 

Over    75    "    i    " 

SECOND  FLOOR 

Up  to  40  sq.ft \  inch 

40  to  100    '.'    f    " 

Over  100    "    i    " 

THIRD  FLOOR 

Up  to    50  sq.ft J  inch 

50  to  125     "    i    " 

Over    125     "    i    " 

The  valves  of  the  radiators  at  the  ends  of  the  mains  are  made 
one  size  larger  than  those  given  in  the  table. 

These  sizes  are  much  smaller  than  those  given  in  the  earlier 
part  of  the  chapter  and  the  areas  of  risers  and  mains  which  are 
made  equal  in  area  to  the  areas  of  the  connections  which  they 
supply  are  also  smaller.  This  is  possible  because  in  times  of 
need  the  temperature  may  be  increased  to  such  a  point  that  the 
circulation  is  rapid  enough  to  care  for  the  heat  needed. 

^  Small  pipes  are  cheaper,  but  beyond  that  there  is  no  advantage 
in  the  small  pipes  except  that  because  the  amount  of  water  in 
the  system  is  less,  the  time  taken  to  get  the  radiators  heated  is 


HOT-WATER  HEATING 


169 


not  great.  Against  this,  however,  the  fact  must  be  remembered 
that  the  system  of  small  water  capacity  will  cool  quicker.  The 
heat  put  into  the  water,  whether  the  mass  be  great  or  small,  is 
to  be  taken  out  by  the  radiators,  so  that  the  volume  of  water 
in  the  system  should  not  affect  the  economy  of  the  system. 

The  method  of  attaching  the  generator  to  one  of  the  upper 
radiators  of  a  system  which  has  been  installed  is  shown  in  Fig. 


FIG.  132. — Generator  Connection. 

132.  In  this  a  branch  has  been  taken  from  the  supply  of  a  unique 
valve  and  carried  to  the  generator,  which  is  then  connected 
to  the  expansion  tank.  In  no  case  should  the  generator  be 
placed  close  under  the  expansion  tank.  The  pressure  produced 
in  the  system  is  independent  of  the  position  of  the  generator. 
The  same  water  column  is  acting  in  addition  to  the  mercury 
wherever  it  is  placed. 

Using  the  methods  given  above  on  the  plans  of  the  residence 


170 


ELEMENTS   OF  HEATING   AND  VENTILATION 


and  the  tables  of  Chapter  V,  the  amount  of  radiation  for  the 
various  rooms  may  be  found.    These  are  given  in  the  table  below : 


Room. 

Sq.Ft. 

Kind. 

Room. 

Sq.Ft. 

Kind. 

I 

170 

3  col.,  38  ins. 

7 

157? 

3  col.,  26  ins. 

2 

1  2O 

3  col.,  38  " 

8 

75 

3  col.,  38  " 

3 

21 

3  COL,  22  " 

9 

22^ 

3  col.,  32  " 

4 

7il 

3  col.,  26  " 

10 

66 

3  COl.,  22  ' 

5 

90 

3  col.,  20  " 

ii 

66 

3  COl.,  22  ' 

6 

126 

3  col.,  45  " 

12 

27 

3  COl.,  22  " 

These  are  now  placed  on   the  development,  and  the  cellar 


FIG.  133. — Arrangement  of  Pipes  and  Boiler  for  Cellar  with  Hot  Water. 

plan,  Fig.  133,  is  made  to  show  the  arrangement  of  flow  lines 
and  boiler. 

The  table  below  gives  the  surface  on  each  riser  and  the  size 
of  the  same. 


Risers          a. 
Surface     163! 
Size  .....  1  1" 


b. 

163! 
i|" 


c. 
135 


d. 
60 
i" 


e. 

43^ 
i" 


f. 
104! 


g. 
33 
i" 


78 


i.         j. 
78       153 


CHAPTER  VIII 

INDIRECT  HEATING 

As  mentioned  in  Chapter  I,  there  are  three  general  methods 
of  indirect  heating.  First,  the  natural-draft  method,  in  which 
heating  coils  are  placed  in  boxes  at  the  bases  of  flues  leading  to 
a  room  or  group  of  rooms.  This  is  used  in  small  installations 
or  residences.  Second,  the  plenum  or  forced  mechanical 
method  in  which  air  is  drawn  over  heating  coils  and  forced 
into  the  various  parts  of  the  building  to  be  heated,  thus  pro- 
ducing in  the  rooms  a  pressure  slightly  above  the  atmosphere. 
Third,  the  vacuum  system  in  which  air  is  drawn  from  the 
rooms  to  be  heated  by  a  fan,  inlet  air  passing  from  the  outside 
over  coils  of  pipe.  In  all  of  these  methods  air  is  used  to  convey 
the  heat  and  in  all  but  the  first  method  there  may  be  con- 
siderable force  to  give  this  air  a  definite  path.  In  the  first 
method  the  heaters  are  placed  at  the  bottom  of  vertical  risers, 
so  there  is  little  resistance  to  the  flow  of  air,  and  this  method 
gives  good  results.  The  boxes  are  placed  at  proper  locations 
through  the  basement  and  supplied  with  steam  from  a  boiler 
at  some  convenient  point.  There  is  no  trouble  experienced 
in  passing  steam  to  remote  indirect  radiators.  The  second  or 
plenum  method  has  the  advantage  of  keeping  the  building 
under  a  pressure  above  the  atmosphere  so  that  leakage  is  out- 
ward, while  in  the  vacuum  system  there  is  a  constant  leakage 
of  cold  air  into  the  room  through  all  loose  windows  or  doors, 
There  are  cases,  however,  where  the  vacuum  method  is  the 
only  one  which  can  be  used,  and  hence  the  student  should 
understand  its  peculiarities. 

The  method  of  procedure  for  the  design  of  indirect  installa- 
tions is  best  illustrated  by  an  application  to  a  given  building. 
The  house  used  in  Chapter  V  will  be  investigated  according 
to  the  method  of  separate  heaters. 

171 


\ 


172         ELEMENTS  OF  HEATING  AND  VENTILATION 

In  the  indirect  system  the  amount  of  air  for  ventilation  is 
first  determined,  then  the  temperature  of  this  air  is  found  so 
that  it  will  supply  the  heat  losses  to  the  room  when  the  air  is 
cooled  off  from  the  inlet  temperature  to  the  temperature  desired 
in  the  room.  After  this,  the  amount  of  heating  surface  needed 
is  computed  and  finally  the  size  of  the  duct  to  properly  carry 
the  air  is  determined.  These  steps  are  common  to  all  three 
indirect  methods  of  heating.  If  the  temperature  of  the  entering 
air  t\  (or  T\  absolute)  is  too  high  for  convenience  or  comfort, 
it  will  be  necessary  to  increase  the  quantity  of  air  beyond  that 
considered  necessary  for  ventilation. 

The  temperature  of  the  air  fixes  the  number  of  rows  of  coils 
or  heaters  in  the  mechanical  system,  although  in  the  natural- 
draft  system  one  set  of  indirect  heaters  is  usually  sufficient,  as 
the  velocity  over  the  radiators  is  low.  The  curves  of  Chapter 
IV  give  these  data. 

If  the  quantity  of  air  per  hour  is  V  cu.ft.  and  the  amount 
of  heat  lost  from  walls  and  windows  per  hour  is  h  in  B.t.u., 
the  following  equation  holds: 

h=Vc(h-tr)       .......       .       (74) 

c  =  heat  necessary  to  raise  i  cu.ft.  i°  F; 
t\  =  temperature  of  entrance  ; 
tr  =  temperature  of  room. 

Hence 

t^t'+Vc  ........     (75) 

now  as  has  been  noted  earlier  in  the  text 


0.  ,   .. 

C=  =°-°2  aPProximately  •    •    -    -     (76) 


#  =  53-34; 

/  =  mean  temperature  of  air  in  deg.  F.  =  T°  absolute  ; 
pb  =  barometric  pressure  in  pounds  per  square  inch. 


INDIRECT    HEATING  173 

This  neglects  the  effect  of  vapor  in  the  air,  although  that 
should  be  considered  for  great  accuracy.  The  reason  for  this 
is  the  fact  that  if  the  vapor  is  considered  in  finding  c  for  the 
mixture,  it  must  be  considered  in  Eq.  (74)  giving  an  additional 
term,  although  the  value  of  c  would  be  smaller.  The  net  result 
would  be  slightly  different  from  the  above  and  hence  this 
approximate  method  is  sufficiently  accurate  for  this  type  of 
problem. 

It  will  be  seen  that  the  heat  in  the  air  above  the  room  tern-  '1 
perature  is  sufficient  to  care  for  the  heat  losses,  as  in  most  cases 
the  hot  air  is  delivered  across  the  ceilings  against  the  cold  walls 
before  it  mingles  with  the  air  of  the  room,  and  hence  by  that 
time  it  is  reduced  to  room  temperature,  and  when  it  returns 
to  the  bottom  of  the  wall  from  which  it  was  discharged  so  as 
to  pass  out  through  the  vent  flue  to  the  roof  it  is  as  the  tem- 
perature of  the  room. 

In  computing  this  temperature  of  entrance  h  for  various 
rooms  in  a  system,  it  is  found  that  the  value  is  quite  different 
for  different  rooms,  because  the  quantities  V  and  h  vary  in  dif- 
ferent ways;  V  for  one  room  may  increase  over  that  in  another 
if  more  people  occupy  the  room,  while  h  might  be  smaller  if 
that  room  were  not  exposed  as  much  as  the  other  room.  For 
this  reason  it  is  not  possible  to  run  a  main  duct  from  the  heater 
in  the  plenum  or  vacuum  systems  and  take  from  it  the  flues 
to  the  various  rooms.  One  of  two  methods  must  be  used. 
In  the  first  method  a  pair  of  ducts  must  be  run  in  the  basement, 
one  carrying  hot  air  and  the  other  warm  air,  and  from  them 
connecting  branches  are  run  to  each  flue  with  mixing  dampers, 
so  that  the  proper  amount  of  each  may  be  had  to  give  the  desired 
temperature.  In  the  second  method  a  separate  duct  must  be 
taken  to  each  flue  from  the  heater  where  both  warm  and  hot 
air  are  supplied  through  mixing  dampers  to  give  the  correct 
temperature  to  each  duct. 

The  first  method  is  known  as  the  double-duct  system  and 
the  second,  the  single-duct  system.  These  were  described  on 
page  13.  The  requirement  of  air  at  two  temperatures  makes 
it  necessary  in  both  of  these  arrangements  of  mechanical  ventila- 


174         ELEMENTS  OF  HEATING  AND  VENTILATION 

tion  to  install  two  heaters,  one  known  as  a  tempering  coil,  to 
heat  all  of  the  air  to  a  low  temperature  and  the  other  to  heat 
a  portion  of  the  air  to  a  higher  temperature  after  separating 
the  air  into  two  parts.  One  temperature  might  be  fixed  by  the 
highest  temperature  necessary,  the  other  by  the  lowest  tem- 
perature necessary. 

In  the  natural-draught  method  of  indirect  heating  there  is 
not  the  necessity  of  having  the  two  temperatures,  as  the  air 
from  each  box  passes  to  its  own  room  or  group  of  rooms.  In 
this  system  the  main  problem  of  design  is  to  get  sufficient  sur- 
face to  give  the  heat  necessary  for  the  room  and  to  get  sufficient 
air  for  ventilation.  Since  the  air  enters  at  about  100°  F.  the 
velocity  for  different  heights  of  flow  may  be  worked  out  as 
follows: 

Weight  of  L  ft.  of  air  at  temperature  h  of  i  sq.ft.  cross- 
sections: 

4/>6L         I44M 

+459.6)  =  ~*rT  .....   (77) 

(T  is  absolute  temperature). 

Weight  of  L  ft.  of  air  at  the  temperature  of  the  outside  air: 

_       144^1,         I44M  ,  ^ 

•~  ' 


The  head  causing  flow  is  the  difference  of  these  if  expressed 
in  pounds  per  square  foot,  or  if  divided  by  the  weight  of  i  cu.ft. 
of  air  at  the  flue  temperature  it  gives  the  head  in  feet  of  air. 

The  weight  of  i  cu.ft.  of  hot  air  is 


_  , 

~R(h  +459-6)  ~ 


Hence  the  head  in  feet  of  the  hot  air  which  is  flowing  through 
the  pipes  is 

L(T,-T0]         L(Ti-T.) 
Head  =  —  ^-^  —  Fi  =  --  ™  --  .        .     .     (80) 


INDIRECT   HEATING  175 

This  head  is  used  in  causing  a  velocity  v  in  the  hot  air  and 
overcoming  friction.  Using  the  general  hydraulic  equation  for 
the  flow  of  a  fluid  the  followin  results  : 


.      .    ...    .     (81) 

v  —  velocity  in  feet  per  second; 
k  =  coefficient  for  entrance  loss  =  f  ; 
n  =  numbers  of  bend  ; 
m  =  coefficient  for  i  bend  =  0.2  ; 
/=  friction  factor  =  0.02  ;  • 

L  =  length  of  pipe  in  feet; 
d  =  diameter  of  pipe  in  feet  ; 

g  =  acceleration   of   gravity  =  3  2.  2   ft.  per   sec.  per    sec. 
If  the  bracket  be  called  Z  the  following  results: 


Head  L(Tl-T) 

~--  •-  •  •  (82) 


For  ri  =  56o,  ro  =  46o,  and  Z  =  2;  this  becomes 

ZJ  =  8.o2Vo.nL     ......     (83) 

These  values  of  V  for  different  floors  are  then  as  follows: 

v  =  6  ft.  per  second  for  5  ft.; 
0  =  8.4  ft.  per  second  for  10  ft.; 
0  =  11.9  ft.  per  second  for  20  ft.; 
0=  14.6  ft.  per  second  for  30  ft.; 
0=16.8  ft.  per  second  for  40  ft. 

Although  these  values  have  been  computed  with  friction, 
the  usual  values  taken  in  design  are  considered  at  about 
half  of  these:  i.e.,  3  ft.  per  second  for  first  floor,  4.2  ft.  per 
second  for  second  floor  5.8  ft.  per  second  for  third  floor  and 
7.3  ft.  per  second  for  fourth  floor. 

Having  the  velocity  for  any  floor  and  the  amount  of  air 
required,  the  size  of  flue  may  be  found. 

V 

A  =—2  -  .     (F  =  cu.ft.  of  air  per  hour)     .     .     (84) 


176         ELEMENTS  OF  HEATING  AND  VENTILATION 

The  amount  of  heating  surface  will  depend'  on  the  amount 
of  heat  required  and  the  rate  of  heat  transmission.  Adding 
together  the  heat  for  ventilation  and  that  for  losses  as  found 
in  the  tables  of  Chapter  V,  the  total  amount  of  heat  is  known. 
The  heat  transmission  per  square  foot  of  area  of  indirect  surface 
depends  on  the  velocity  and  until  this  is  known  only  an  approx- 
imate value  can  be  had.  Assuming  this  to  be  300  B.t.u. 
the  surface  required  will  be  given  by 


If  now  the  area  between  the  sections  to  give  this  surface 
be  found  then  the  velocity  may  be  found  : 

(86) 


t 
3600.4  h 

of  passages  in  heater.  Experiments  seem  to 
indicate  that  with  natural  draft  radiators  the  heat  transmis- 
sion coefficient  equals  the  square  root  of  the  velocity.  This 
means 

fc-^[,-<^]     .....     (87) 

/Zi=B.t.u.  transmitted  per  hour  per  square  foot; 
ts  =  temperature  of  steam  or  mean  temperature  of  water 

in  degrees  F. 

t0  =  temperature  of  outside  air; 
/i  =  temperature  of  air  entering  room; 
i)  =  velocity  over  coils  in  feet  per  second. 

In  this  way  the  heat  per  square  foot  may  be  found  and  from  it, 
the  surface.  It  may  be  necessary  to  make  two  approximations 
before  the  area  found  agrees  with  that  required  to  give  the 
k\  assumed. 

After  this  is  computed  the  ducts  leading  to  the  outside  are 
found.  In  determining  these  the  velocity  should  be  assumed  to 
be  that  in  the  inlet  passages.  In  -fact  this  velocity  might  be 


INDIRECT   HEATING 


177 


assumed  to  be  the  velocity  over  the  coils  or  sections  of  the 
heater  and  the  distance  between  sections  so  made  that  this  is 
obtained.  In  figuring  areas  for  cold  air  the  volume  of  this  air 
must  be  found. 

The  application  of  this  method  to  room  i  of  the  house  leads 
to  the  following: 

Volume  air  per  hour  6200  cu.ft. 


16810 


6200  Xo.oiS 


+  70  =  226°  F. 


FIG.  134. — Cellar  Plan  for  Indirect  Heating. 

This  is  too  high,  so  the  quantity  of  air  must  be  increased. 
Assume  this  to  be  six  changes  per  hour. 


16810 


+  70  =  120°  F. 


18600X0.018 
This  is  a  possible  value. 

H=  16810+70X0.018X18660  =  40300. 


178          ELEMENTS   OF  HEATING  AND  VENTILATION 
Velocity  4  ft.  per  second. 


I20 


227-  —  -    -    =334; 


40300 

o  =  ~     —  =  120  sq.ft.; 
334 

18660X144 

Ah=-  -  =186.6  sq.m. 

4X3600 

The  table  below  gives  the  data  for  the  complete  house  and 
Fig.  134  illustrates  the  layout  in  cellar  to  accomplish  the 
result. 


Ventilation. 

Room 

Heat 
Loss. 

tl 

Total 
H. 

V 

h 

s 

Actual 
».* 

Area 
Flue. 

Ratio. 

Chap. 

Used. 

I 

16810 

6200 

18600 

120 

40300 

4 

334 

1  20 

1  2O 

187 

26 

2 

11792 

4300 

14000 

117 

29400 

4 

334 

90 

96 

140 

22 

3 

1745 

800 

2000 

118 

4300 

4 

334 

13 

16 

2O 

25 

4 

6890 

2800 

8000 

113 

16900 

4 

334 

5i 

56 

80 

25 

5 

8740 

3200 

IOOOO 

119 

21300 

4 

334 

64 

64 

100 

25 

6 

10635 

3200 

I200O 

119 

25700 

4 

334 

78 

80 

120 

2? 

7 

14050 

2910 

I6OOO 

119 

34100 

5-6 

394 

87 

88 

II4 

33 

8 

8750 

20OO 

IOOOO 

119 

21300 

56 

394 

54 

56 

72 

36 

9 

2170 

720 

3000 

no 

5700 

5-6 

394 

15 

16 

22 

44 

10 

7680 

I7OO 

9000 

117 

19000 

5-6 

394 

48 

48 

65 

26 

ii 

8330 

1710 

IOOOO 

116 

21000 

5-6 

394 

53 

56 

72 

25 

12 

2840 

480 

3500 

US 

6OOO 

5-6 

394 

15 

16 

25 

19 

*  Using  Junior  Indirect  Radiators. 

The  ducts  leading  the  air  to  the  boxes,  the  boxes  and  the 
flues  are  made  of  galvanized  iron,  although  in  many  cases  the 
flues  are  made  of  tin  as  will  be  given  more  in  detail  in  the  next 
chapter.  Each  duct  leading  to  the  outside  should  have  a  slide 
so  that  cold  air  may  be  cut  off  should  there  be  any  danger  of 
the  steam  being  shut  off.  A  damper  should  be  put  in  each  duct 
and  it  is  well  to  have  register  faces  with  closing  flaps. 

The  galvanized  iron  should  be  of  proper  gauge  to  give  suf- 
ficient stiffness.  For  round  pipes  the  manufacturers  of  heating 
apparatus  recommend  the  following: 


INDIRECT   HEATING 


179 


Diameter. 

up  to  1 8' 
19  to  24' 
30  to  39' 
40  to  49' 
50  to  70' 


Gauge. 
26 
24 
22 
20 

18 


Rectangular. 

up  to  6  X  6 
7X7  to  12X12 
13X13  to  20X20 
21X21  up 


For  rectangular  ducts  the  limiting  square  is  given.  The 
guage  used  is  the  U.  S.  standard  sheet  metal  gauge.  The  gauge 
numbers  stand  for  the  following  thicknesses: 


Gauge  No 28  26 

Thickness A"  ilV 

Gauge  No 10        8 

Thickness..  .A"  Ji" 


24 

A" 

6 

tt" 


22 
1  // 
3^ 

4 

JL5// 

t.  1 


20 

A" 


tt' 


18 

i  // 

2¥ 
O 

A" 


16       14 

A"    A" 

ooo 


nn 

nn 

nnnnnnnnnn 

^n 

Dn 

Dnnnnnnnn^ 

DC 

nn 

^nnnnnnnnn 

nn 

unnnnnnnnn 

M 

nn 

D 

nn 

nnn 

n 

nnn 

H 

^ 

nn 

n 

nn 

nnn 

n 

nnn 

B 

~ 

nn 

D 

nn 

nnn 

n 

nnn 

6 

~ 

nn 

j 

nn 

nnn 

n 

nn^ 

D 

J 

nn 

n 

un 

nnn 

n 

nnn 

FIG.  135. — Register  Faces. 

The  register  faces  are  of  various  sizes  and  designs.  Fig.  135 
illustrates  two  typical  forms  of  these.  They  are  usually  made 
with  dampers.  They  vary  from  4X6"  around  body  (sf  Xyf 
extreme  size),  to  38X42"  (40! X44f).  The  variations  are  by 
i  to  4"  on  a  side  so  that  almost  any  size  may  be  obtained.  For 
special  work  large  sizes  may  be  had. 

The  net  area  of  the  register  amounts  to  about  66  per  cent 
of  the  box  or  body  area. 

A  school  building  has  been  selected  to  illustrate  the  method 
of  calculating  a  plenum  system,  on  account  of  the  small  quantity 
of  air  required  for  a  house.  After  this  the  method  will  be  applied 
to  a  shop  building. 

Figs.  136,  137  illustrate  the  basement  and  second  floor 
of  a  school  building.  There  are  three  floors  to  the  school,  all" 
floors  being  the  same. 


180         ELEMENTS  OF   HEATING  AND  VENTILATION 

The  amount  of  ventilation  has  been  computed  by  allowing 
1800  cu.ft.  per  pupil,  which  is  the  amount  required  by  law  in 


Fl3. 136.— Basement  of  School  No.  3,  Rydal,  N.  Y. 


FIG.  137.— Second  Floor  of  School  No.  3,  Rydal,  N.  Y. 

some  States.     This  is  rather  a  large  amount,  especially  in  the 
lower  grades  and  could  be  reduced  if  it  were  not  for  the  law. 


INDIRECT  HEATING  181 

The  amount  required  by  various  authorities  has  been  given  in 
Chapter  II. 

The  heat  loss  from  the  various  rooms  considering  the  exposure 
and  other  elements  has  been  computed  in-  a  manner  similar  to 
that  described  in  Chapter  V  and  the  results  of  this  computation 
are  shown  in  the  table  on  page  182. 

The  temperatures  assumed  for  this  school  have  been  70°  in 
zero  weather.  The  column  marked  "  air  temperature  "  gives 
the  temperature  of  air  entering  the  room  from  the  flue. 

The  first  computations  to  be  made  are  those  from  the 
heater.  The  temperatures  of  the  hottest  air  and  coolest  air 
show  that  the  air  could  be  heated  to  71°  F.  and  a  portion  to 
89°  F.  Then  by  properly  adjusting  all  dampers  the  necessary 
mixture  temperatures  could  be  had.  In  the  present  instance, 
though,  the  temperature  of  the  tempered  air  will  be  70*  F., 
and  the  remainder  will  be  heated  to  such  a  temperature  that  the 
total  heat  will  be  equal  to  that  required  for  the  building. 

Total  heat  for  building  =3,052,000  B.t.u. 

Heat  for  tempering  coil  =2,541,000  B.t.u. 

Heat  from  main  coil  =    511,000  B.t.u. 
Temperature  of  air  discharged  from  ^  OQQ 

main  coil  if  one-half  is  heated  = ——3 —r  +70° 

0.02X181500X1 

=  98°F. 

The  problem  will  be  worked  out  using  Vento  heaters  and  then 
with  pipe  coils,  the  steam  being  at  5  Ibs.  pressure  in  zero  weather. 

From  the  Vento  heater  curves,  Figs.  89-90,  it  is  seen  that  70° 
is  given  by  2  sections  at  a  velocity  of  730  ft.  per  minute,  or  by 
3  sections  at  1700  ft.  per  minute.  From  Fig.  91,  i  section  of  4 
rows  of  pipes  at  190  ft.  per  minute,  2  sections  at  370  ft.,  3  sec- 
tions at  800  ft.,  4  sections  at  1600  ft.  would  give  a  temperature 
.  of  70°  if  pipe  coils  were  used. 

The  high  velocities  would  mean  much  friction  and  the  low 
velocities  would  probably  require  too  much  space.  The  velocity 
of  1000  ft.  per  minute  is  a  fair  value,  so  that  in  the  problem 
the  velocity  of  730  might  be  used  for  the  Vento  heater  and 
800  ft.  per  minute  if  pipe  coils  are  used.  These  values  will  be 


182 


ELEMENTS   OF  HEATING  AND   VENTILATION 


REQUIREMENTS  FOR  SCHOOL  No.  3 

RYDAL,  N.   Y. 


First  Floor 


Second  Floor 


Room 
No. 

Occu- 
pants. 

Cubic 
Feet. 
Ventila- 

Heat 
Loss. 

Air 
Temp. 

Room 

i  No. 

Occu- 
pants. 

Cubic 
Feet. 
Ventila- 

Heat 
Loss. 

Air 
Temp. 

tion. 

l 

tion. 

I 

49 

88200 

29100 

86 

7 

49 

88200 

29000 

86 

I  A 

— 

6000 

1800 

85 

7  A 

— 

6000 

1800 

85 

2 

49 

88200 

27000 

85 

8 

49 

88200 

26000 

85 

2A 

— 

6000 

1500 

83 

8A 

— 

6000 

1500 

83 

3 

49 

88200 

2IOOO 

82 

9 

49 

88200 

2OOOO 

8l 

3A 

— 

6000 

I50O 

85 

pA 

— 

6000 

I800 

85 

4 

49 

88200 

19000 

81 

10 

49 

88200 

18000 

So 

4A 

— 

6000 

I5OO 

83 

zoA 

— 

6000 

1500 

83 

5 

49 

88200 

33000 

89 

ii 

49 

88200 

32000 

88 

5A 

— 

6000 

1800 

85 

nA 

— 

6000 

I800 

85 

6 

49 

88200 

25000 

84 

12 

49 

88200 

24OOO 

84 

6A 

— 

6000 

I800 

85 

I2A 

— 

6000 

1800 

85 

75 

'  Halls 

6OOOO 

IOOOO 

71 

Halls 

^OOOO 

r?OOO 

Total 

625000 

174200 

Total 

CQCOOO 

162200 

Third  Floor 


Room  No. 

Occupants. 

Cubic  Feet 
Ventilation. 

Heat  Loss. 

Air 
Temperature. 

13 

49 

88200 

30000 

87 

I3A 

— 

6000 

1800 

85 

14 

49 

88200 

28000 

86 

I4A 

.  •    — 

6000 

1500 

83 

i5 

49 

88200 

22000 

83 

ISA 

— 

6000 

I800 

85 

16 

49 

88200 

2OOOO 

81 

i6A 

— 

6000 

1500 

83 

i? 

49 

88200 

34000 

89 

i7A 

— 

6000 

I800 

85 

18 

49 

88200 

26OOO 

85 

i8A 

— 

6000 

1800 

85 

Halls  

30000 

4OOO 

77 

Total  

59  5OOO 

I  742OO 

Grand  total.  . 

1815000 

510600 

Heat  for  air 

2541000 

Total  heat  B  t 

u 

3051600 

INDIRECT  HEATING  183 

used,  although  in  the  remaining  calculations  it  may  be  necessary 
to  make  a  different  assumption  for  the  temperature  of  the  tem- 
pered and  heated  air. 

From  the  curves  of  Chapter  IV  the  heating  value  of  the 
surface  may  be  found.  Fig.  90  gives  the  heat  per  square  foot 
per  hour  at  730  ft.  per  minute  with  2  sections  as  1456  B/t.u., 
while  1750  B.t.u.  will  be  given  off  per  square  foot  of  coil  surface. 

The  square  feet  of  heating  surface  required  for  the  temper- 
ing coil  will  be: 

For  Vento  heaters  2'54I'°—  =  1750  sq.ft. ;     , 
1450 

For  Buffalo  Forge  coils  —  —  =  1450  sq.ft. ; 

The  area  in  square  feet  required  through  these  heaters  is 

For  Vento  heaters  —  — ^~^=4I-5  sq.ft.: 
730X60 


The  data  sheets  for  Vento  heaters  and  coils  of  one  com- 
pany are  given  below,  and  from  these  the  following  is  found: 

1750  sq.ft.  in  2  sections  — 875  sq.ft.  per  section.  Use  3  stacks 
of  1 9  sections  =  91 2  sq.ft.  For  4§  ins.  center, area  =  3X14.83  =44. 5 
sq.ft. 

This  is  sufficiently  close  to  41.5  to  give  little  change  in  velocity. 

For  the  pipe  coils  1450  sq.ft.  =4210  lin.ft. 

Each  section  must  contain  1403  lin.ft.  Hence  use  2-6-ft.-2E 
heater  units  in  each  section.  The  area  is  21.2  X  2  =42.4,  which 
is  close  enough  to  give  the  proper  velocity. 

In  each  of  the  above  cases  the  area  was  large  and  conse- 
quently the  velocity  would  be  low.  This .  would  reduce  the 
heat  transmission  and  require  more  surface.  This  is  not 
necessary  in  the  cases  above. 

The  tables  give  the  over-all  dimensions  of  these  heaters 
with  the  allowance  for  staggering.  The  Vento  heater  of  6  stacks 
will  require  (3X88"  +  5"+.io'/)X(2Xio"+4//)X6o//  =  279//  x 

24"x6o"  high. 


184         ELEMENTS   OF  HEATING  AND  VENTILATION 
The  Buffalo  coils,  (2  X  7'-  io")X  (3X8^0X72"  • 

iS'-8"X24i"X72". 

To  reduce  the  column  headed  lineal  feet  of  i-in.  pipe  in  the 
table  of  the  Buffalo  Forge  coils  to  square  feet,  the  numbers 
are  divided  by  2.9. 

In  regard  to  the  Vento  heater  it  is  to  be  remembered  that  the 
makers  build  a  narrow  section  containing  about  three-quarters 
of  the  heating  surface  of  the  regular  section,  but  having  the 
same  dimensions  in  height  and  width  with  the  same  air  space. 

Both  forms  of  heaters  are  in  common  use;  some  designers 
prefer  one,  some  the  other. 

To  find  the  number  of  sections  to  use  in  the  main  heater, 
the  number  of  sections  must  be  found  to  give  the  required 
temperature  of  the  hot  air  and  from  this  the  number  used  in 
the  tempering  coils  must  be  subtracted. 

Thus  at  730  ft.  per  minute  3  sections  of  Vento  heaters  must 
be  used  to  give  98°  F.,  and  at  800  ft.  per  minute  4^  sections  of 
coils  must  be  used  to  get  this  temperature.  This  latter  means 
5  sections.  The  heating  coils  will  then  be  made  of  i  section  of 
Vento  heater  or  2  sections  of  coils.  The  surface  required  is 
found  as  follows: 

From  curves,  Fig.  900,  for  Vento  heater: 

3X1340-2X1450 
h  =  -  —          -  =  1120; 

511,000 

Area  =  -  =  456. 
1120 

From  curves,  Fig.  920,  for  coils: 


OO7 

Area  for  air  passage  =  --  ;—  7-  =  20.  7  for  Vento; 


INDIRECT  HEATING 


185 


For  the  Vento  heater  i  stack  of  28  60  in.  sections,  4§-in.  centers, 
will  be  used  giving  448  sq.ft.  and  21.86  sq.ft.  area  for  air 
passage.  For  the  coil: 


385  sq.ft.  =  1120  lin.ft.  per  section; 

2  sections  of  560  lin.ft.  per  section; 

5-ft.  section  $D  will  be  used  with  a  \  section. 

This  gives  567  lin.ft.  and  16.8  sq.ft.  area. 


SIZES   AND    DIMENSIONS  OF  BUFFALO  STANDARD   FAN  SYSTEM 

HEATER 


Length  of 
Section. 

Section  No. 

Extreme 
Height  of 
Heater. 

Width  of 
Section. 

Lineal  Feet 
of  i  -inch 
Pipe  per 
Section. 

Area  for  Air 
Passage, 
Square  Feet. 

Weight. 

lA 

3'    4" 

8*" 

158 

5-1 

423 

2A 

3    10 

8| 

I78 

5-4 

454 

3' 

3A 

4      4 

8* 

193 

6.1 

477 

4  row 

4A 

4    10 

8| 

221 

6.9 

520 

5A 

5      4 

8| 

249 

7-7 

564 

6A 

5    10 

8| 

277 

8-5 

607 

iB 

5'    4" 

81" 

320 

9-8 

739 

4' 

2B 

5    10 

81 

356 

10.8 

795 

4  row 

3B 

6      4 

8| 

392 

n.  8 

850 

4B 

6    10 

8| 

428 

12.9 

906 

iC 

5'  10" 

si" 

396 

12  .O 

881 

4'  6" 

2C 

6     4 

8^ 

436 

13.0 

943 

4  row 

3C 

6    10 

8£ 

477 

14.0 

1006 

4C 

7      4 

8| 

5i6 

15-0 

1066 

iD 

6'    4" 

8|" 

479 

14-3 

1046 

5' 

2D 

6    10 

8| 

523 

15-6 

1114 

4  row 

3D 

7      4 

8^ 

567 

16.8 

1185 

4D 

7    10 

8| 

611 

17-8 

1251 

lE 

7'     4" 

8*" 

670 

19.7 

1388 

6' 

2E 

7    10 

8| 

722 

21  .  2 

1479 

4  row 

3E 

8     4 

81 

774 

22.7 

1549 

4E 

8    10 

8| 

826 

24.2 

1630 

iF 

8'    4" 

6" 

480 

27.0 

1039 

7' 

2F 

8    10 

6 

512 

29.0 

1089 

2  row 

3F 

9     4 

6 

544 

30.8 

1138 

4F 

9    10 

6 

576 

32.5 

1188 

From  Catalogue  197,  Buffalo  Forge  System. 


186 


ELEMENTS  OF  HEATING  AND  VENTILATION 


VENTO  CAST-IRON   HOT-BLAST   HEATER 
REGULAR  SECTION,  RATINGS  AND  FREE  AREAS 

Regular  40"  Section,  10.75  square  feet.     Height  416*4".     Width 


S"  Centers  of 

Si"  Centers  of 

4f  "  Centers  of 

Loops. 

Loops. 

Loops. 

No.of 
Loops 

Square 
Feet  of 
of 

*Equiv- 
alent 
in 

Standard  44% 
of  Face. 

52%  of  Face. 

37%  of  Face. 

Actual 
Weight 

Ap- 
proxi- 

in 
Stack 

Heating 
Surface. 

Lin.  Ft. 
i  -inch 
Pipe. 

of  Stack 
in 
Pounds. 

mate 
W'ght. 

Net  Air 
Space  in 
Square 
Feet. 

t  Width 
Statk  in 
Inches. 

Net  Air 
Space  in 
Square 
Feet. 

t  Width 
Stack  in 
Inches. 

Net  Air 
Space  in 
Square 
Feet. 

t  Width 
Stack  in 
Inches. 

7 

75-25 

226 

4-34 

35 

5-12 

38 

3.67 

32 

594 

8 

86.00 

258 

4.96 

40 

5.8s 

43 

4.20 

37 

670 

*• 

9 

96.75 

290 

5-58 

45 

6.57 

48 

4-72 

42 

728 

• 

10 

107.50 

323 

6.  20 

50 

7.29 

54 

5-25 

46 

851 

*CC    S 

n 

118.25 

355 

6.82 

55 

8.02 

59 

5-77 

936 

5  ^ 

12 

129.00 

387 

7.44 

60 

8.74 

65 

6.30 

55 

IO22 

«« 

13 

139-75 

419 

8.06 

65 

9-47 

70 

6.82 

60 

Il67 

jj  *EL 

14 

150.50 

452 

8.68 

70 

10.  19 

75 

7-35 

65 

1193 

£  a 

IS 

161.25 

484 

9.30 

75 

10.91 

81 

7.87 

69 

1278 

a'jS 

16 

172.00 

9-92 

80 

n  .64 

86 

8.40 

74 

1364 

"  M 

17 

182.75 

548 

10.54 

85 

12.36 

91 

8.92 

79      i     1449 

cLii 

18 

193.50 

58l 

n  .  16 

90 

13.09 

97 

9-45 

83 

1535 

</j  ^ 

19 

204.25 

613 

n  .78 

95 

13.82 

IO2 

9-97 

88      i     1620 

20 

215  .00 

645 

12.40 

100 

14-54 

108 

10.50 

92      !     1706 

"T  <u 

21 

225.75 

677 

13.02 

105 

15.26 

113 

n  .02 

97           1790 

r*   Q, 

22 

236.50 

710 

13.64 

no 

iS-98 

118 

ii.SS 

IO2        !      1876 

tluj 

23 

247.25 

742 

14.  26 

us 

16.71 

124 

12.07 

106          1960 

£ 

24 

258.00 

774 

14.88 

1  20 

17-43 

129 

12.60 

in 

2045 

o\ 

Regular  50"  Section,  13.5  square  feet.     Height  soff".     Width  9|". 


5"  Centers. 

5|"  Centers. 

4f"  Centers. 

7 

94-5 

284 

5-37 

35 

6.35 

38 

4-55 

32 

717 

8 

108.0 

324 

6.14 

40 

7-25 

43 

5.20 

37 

8  10 

^, 

9 

121.  5 

365 

6.91 

45 

8.15 

48 

5-85 

42 

923 

.  bo 

10 

135-0 

405 

7.68 

50 

9-05 

54 

6.50 

46 

1026 

"rt'S 

II 

148.5 

446 

8.45 

55 

9-95 

59 

7.15 

Si 

1129 

5  ^ 

12 

162.0 

486 

9.22 

60 

10.85 

65 

7.80 

55 

1232 

£  2? 

13 

175-5 

527 

9-99 

65 

11-75 

70 

8.45 

60 

1335 

to  c 

.  **-• 

14 

i8?.o 

567 

10.76 

70 

12.65 

75 

9.  10 

65 

1436 

-^  O. 

«*H     p, 

IS 

202.5 

608 

n.53 

75 

13-55 

81 

9-75 

69 

1539 

V"£ 

16 

216.0 

648 

12.30 

80 

14-45 

86 

10.40 

74 

1644 

*"         IO 

17 

229.5 

689 

13.07 

85 

15-35 

91 

ii  .05 

79 

1747 

8£ 

18 

243.0 

729 

13.84 

90 

16.25 

97 

11.70 

83 

1852 

Pi^ 

19 

256.5 

770 

14-59 

95 

17-iS 

IO2 

12.35 

88 

1955 

j£ 

20 

270.0 

810 

15.36 

100 

18.05 

108 

13.00 

92 

2060 

"""'   O 

21 

283.5 

851 

16.  13 

105 

18.95 

H3 

13.65 

97 

2160 

o  a 

22 

297-0 

891 

16.90 

no 

19.85 

118 

14.30 

102 

2263 

tC.  <n 

23 

310.5 

932 

17.67 

us 

20.75 

124 

14-95 

1  06 

2370 

,0 

24 

324-0 

972 

18.44 

120 

21.65 

129 

15-60 

III 

2470 

o 

*  The  actual  length  of   i-inch  pipe  per  square  foot  of  outside  surface  is  2.9  lineal  feet 
but  is  nominally  figured  at  3  lineal  feet,  as  shown  in  the  third  column  of  above  table. 
t  Add  to  the  width  of  stack  2\  inches  for  staggering  oi  stacks. 
Taken  from  American  Radiator  Co.  Catalogue. 


INDIRECT  HEATING 

Regular  60"  Section,  16  square  feet.     Height  6oH"-     Width 


187 


5"  Centers. 

5f"  Centers. 

4f"  Centers. 

7 

112.  O 

336 

6.4S 

35 

7.62 

38 

5-47 

32 

864 

8 

128.0 

384 

7-37 

40 

8.70 

43 

6.25 

37 

988 

«a 

9 

144.0 

432 

8.29 

45 

9-77 

48 

7-03 

42 

III2 

J3 

M 

10 

1  6O.O 

480 

9.21 

50 

10.85 

54 

7-81 

46 

1238 

..H 

*cS  4) 

II 

176.0 

528 

10.  13 

55 

11-93 

59 

8.59 

51 

1362 

S* 

12 

I92.O 

576 

11.05 

60 

13.00 

65 

9-37 

55 

I486 

tj  SO 

13 

2O8.0 

624 

11.97 

65 

14.08 

70 

10.15 

60 

1610 

03   C 

•3 

14 

224.0 

672 

12.89 

70 

15.15 

75 

10.93 

65 

1734 

dS 

15 

24O.O 

720 

13.81 

75 

16.23 

81 

11.71 

69 

1858 

rf'rt 

16 

256.0 

768 

14-73 

80 

17.31 

86 

12.49 

74 

1982 

MM 

17 

272.O 

816 

15-65 

85 

18.39 

9i 

13.27 

79 

2106 

fe«J 

18 

288.O 

864 

t6.57 

90 

19-46 

97 

14-05 

83 

2230 

^o1 

19 

304.0 

912 

17.50 

95 

20.54 

102 

14-83 

88 

2352 

</i  w 

20 

32O.O 

960 

18.42 

100 

21.62 

I  O8 

15  .61 

92 

2478 

_n  ^ 

21 

336.0 

1008 

19-34 

105 

22.70 

H3 

16.39 

97 

2600 

^0, 

22 

352.0 

1056 

20.26 

no 

23.78 

118 

17.17 

102 

2725 

t-~    . 

23 

368.O 

1104 

21.  18 

US 

24-85 

124 

17-95 

1  06 

2850 

*":2 

24 

384.0 

1152 

22.  10 

1  20 

25-93 

129 

18.73 

in 

2970 

Oi 

The  size  of  the  supply  and  return  for  these  heaters  is  found 
by  determining  the  weight  of  steam  condensed  and  then  using 
one  of  the  three  methods  given  in  the  previous  chapter. 

Heat   from   heater   per   hour 
Weight  of  steam  per  hour  =  -  :  -  -  -  ; 


i  =  heat  content  of  the  entering  steam  ; 

<70  =  heat  of  liquid  at  temperature  of  return. 

The  covering  around  the  heaters  is  usually  made  of  sheet 
iron  of  about  No.  18  or  No.  20.  This  is  put  together  with 
stove  bolts  so  that  the  apparatus  may  be  taken  apart  when 
necessary.  The  casing  should  lead  to  the  inlet  and  doors  should 
be  provided  for  inspection  'of  all  parts. 

The  air  should  be  drawn  through  a  wire  screen  to  prevent 
leaves  and  sticks  from  entering,  or  air  washers  of  the  forms 
shown  in  Chapter  II  may  be  used. 

The  design  of  the  flues  and  ducts  is  next  considered. 

Flow  of  Air.  There  is  a  loss  of  pressure  due  to  friction  as  air 
flows  through  piping.  This  loss  as  in  all  fluids  varies  directly 
as  the  length  of  piping  considered;  inversely  as  the  hydraulic 
radius  of  the  pipe,  which  is  the  ratio  of  the  area  of  the  pipe  to 
its  perimeter,  and  directly  as  some  power  of  the  velocity  of  the 
air.  There  are  two  velocities  to  be  noted.  At  a  low  velocity 
the  air  is  found  to  travel  in  parallel  lines  and  under  these  con- 


188 


ELEMENTS   OF  HEATING  AND  VENTILATION 


ditions  the  friction  varies  as  the  first  power.  On  increasing  the 
velocity  beyond  that  giving  parallel  flow,  the  limit  of  which 
is  known  as  the  critical  velocity,  the  air  is  found  to  have  a 
turbulent  passage  and  friction  varies  as  the  square  of  the  velocity. 
As  most  velocities  used  are  beyond  the  critical  velocity,  this 
latter  method  is  the  only  one  to  be  considered. 

There  are  several  methods  of  stating  the  pressure  in  gases. 
One  method  is  in  ounces  per  square  inch,  or  pounds  per  square 
inch,  above  the  atmosphere.  Another  method  is  in  inches  or 
feet  of  water,  which  means  the  distance  the  water  will  rise  in  a 
U  tube  when  connected  to  the  system  carrying  the  air  on  one 
leg  while  the  other  leg  is  connected  to  the  atmosphere.  A 
still  further  method  is  to  express  this  in  feet  of  the  air  or  gas 
considered.  This  expression  gives  the  height  to  which  the 
column  on  one  side  of  a  U  tube  would  rise  beyond  the  level  in 
the  other  if  the  substance  were  air  or  gas  of  constant  density 

equal  to  that  of  the  air  at  the  point, 
and  the  U  tube  were  connected  as 
mentioned  above  and  shown  in  Fig 
138.  Another  way  in  which  to  ex- 
plain this  is  to  say  that  the  pressure 
or  head  of  so  many  feet  of  a  sub- 
stance means  the  height  of  a  column 
of  substance  one  square  inch  in 

A-SSSSSSS  is>>>^>^ss^s^^^?^      cross-section  which  would  weigh  an 

amount  equal  to  the  pressure  per 
I^^^^^^^^^^J      square  inch.     Thus  if  h  equals  the 

FIG.  138—1;  Tube.  *eet  nea<^  °^  a  substance  and  hi  the 

head  in  inches,  w  the  weight  of  a 

cubic  foot  in  pounds,  W  the  total  weight  in  pounds,  p  the 
pressure  in  pounds  per  square  inch,  and  p0  the  pressure  in 
ounces  per  square  inch,  the  following  equations  hold: 


144 
r^ 


w 


w 


(88) 
(89) 


INDIRECT  HEATING  189 
For  water                     20  =  62.5  Ibs. 

/*  =  2.30^  =  0.144^0 (go) 

ht=  27.60^  =  i.  728^ (91) 


For  air  or  gas 


RT 


,    , 
(92) 


where  p  =  pressure  in  pounds  per  square  inch. 

R  =  53.34  for  air (93) 

~  mol.  density  for  any  gas 
T  =  absolute  temperature  in  degrees  F. 

The  pressure  p  is  the  total  pressure  on  the  air  and  is  equal  to 
the  barometric  pressure  plus  that  above  the  atmosphere. 
In  general  for  air  at  atmospheric  pressure  and  70°  F. 

144X14-7X1  i     „  ,    ^ 

w  =  —        —r^          — N  =0.0748  = Ibs.    .     .     (95) 

53-34X  (459-6  +  70)  13-3 

Hence 


.     .     .     (96) 

featt  =  1440  A> (97) 

The  relation  between  inches  of  water  and  inches  of  air  at 
70°  and  atmospheric  pressure  is  given  by 

^  =  ^  =  ^=T2o' (98) 

or 

1 20  hi 
^lr  =  T7^f  =  69'5^      ••••;•     (99) 

hi  air  =  69.5X12^ 

=  835.0^ (100) 


190 


ELEMENTS  OF  HEATING  AND  VENTILATION 


The  subscripts,  "  air  "  and  "  ze!,"  refer  respectively  to  head 
in  feet  or  inches  of  air  or  water. 

If  a  set  of  tubes  is  placed  in  the  side  of  a  pipe  line  carrying 
air  or  other  gas,  these  heads  or  heights  represent  the  distances 


FIG.  139. — Loss  in  Head. 

to  which  the  air  would  rise  if  of  uniform  density  due  to  the 
pressure  of  the  pipe.  If  now  there  were  two  of  these  tubes, 
known  as  piezometers,  placed  at  two  points  on  a  line  as  shown 
in  Fig.  139,  the  difference  in  level  would  show  the  loss  in 
pressure  due  to  friction.  The  question  of  correctly  measuring 


FIG.  140. — Piezometers. 

the  static  pressure  in  a  line  carrying  gas  with  some  velocity  is 
of  importance.  The  best  manner  is  to  have  a  tube  attached 
to  the  wall  of  the  pipe  absolutely  perpendicular  and  finished 
flush  with  the  surface  as  shown  in  Fig.  At  140,  or  a  tube  may  be 
introduced  as  shown  in  the  figure  on  which  is  a  large,  normal 
disc  with  sharp  edges.  The  purpose  of  the  disc  is  to  cut  out 


INDIRECT  HEATING 


191 


eddies  which  form  around  any  tube  and  give  incorrect  readings. 
Aspiration  effect  is  usually  produced  by  the  tube  entering  as 
at  C,  Fig.  140,  although  there  may  be  an  increase  of  pressure 
due  to  impact  of  the  air.  The  introduction  of  a  tube  as  at  Z>, 
Fig.  140,  will  give  a  pressure  reading  equal  to  the  sum  of  the 
static  pressure  and  the  pressure  due  to  velocity  and  for  that 
reason  it  is  sometimes  called  the  dynamic  pressure.  The  dif- 
ference between  the  dynamic  pressure  and  the  static  pressure  is 
the  velocity  pressure  or  the  Pitot  pressure.  A  Pitot  tube  is  a 
tube  bent  in  the  direction  of  the  flow  connected  through  a  U 


FIG.  141.— Pitot  Tube. 

tube  to  a-  static  pressure  tube,  Fig.  141.  In  this  way  the  pres- 
sure in  inches  of  water  due  to  the  velocity  may  be  found.  Exper- 
iment and  theory  indicate  that  if  this  pressure  be  reduced  to 
feet  of  the  substance  carried  in  the  pipe  the  velocity  is  given 
by  the  equation 


flair  = 


Or       alr  = 


2? 


(101) 


/zalr  =  feet  of  air  equal  to  difference  in  pressure  between 

the  static  and  dynamic  pressure; 
^air =  velocity  of  air  in  feet  per  second; 
#  =  32.174  acceleration  of  gravity; 


192 


ELEMENTS  OF  HEATING  AND  VENTILATION 


since 


^  =  69.5  hiw  (for  70°  and  atmospheric  pressure) 

flair  =V/2gX  69.5;^  =  66. 


(l02) 


These  two  tubes  are  sometimes  combined  in  one  as  shown 
in  Fig.  142,  but  such  a  tube  is  apt  to  give  incorrect  read- 
ings because  the  static  tube  is  subject  to 
eddy  currents.  The  objection  to  the  single 
static  tube  at  the  wall  is  that  the  pressure 
may  not  be  thought  to  be  constant  over 
the  section  of  the  flue,  but  experiment 
seems  to  indicate  that  the  pressure  is  uni- 
form. 

The  loss  in  pressure  due  to  friction 
may  now  be  discussed.  The  usual  method 
is  to  express  the  loss  in  feet  of  head  of  the 
fluid  being  carried.  Experiment  then  gives 
(beyond  the  critical  velocity) : 

/  . 


FIG.  142. — Arrangement 
of  Pitot  Tube  with 
Static  and  Dynamic 
Tube  Together. 


(A=  area  in  square  feet,  p 
/  =  length  in  feet. 


_^L_A        d 

~  p  ~  id  ~~4 
perimeter  in  feet); 


(103) 


(104) 


Before  reducing  this  it  is  well  to  note  that  since  velocity  pressure 
head  is  given  by 


it  is  well  to  introduce  2g  into  the  expression  above  for  con- 
venience and  then  reducing  by  use  of  the  other  quantities,  the 
value  of  hf  becomes  for  round  pipes, 


A 


2g 


(105) 


INDIRECT  HEATING  193 

For  square  pipes  the  same  expression  holds,  while  for  rectan- 
gular pipes  of  height  d  and  breadth  2d  the  expression  for  r 
becomes 


6da 

In  this  case  /"  for  such  a  pipe  becomes 

/=!/;/ ~r (lo6) 


The  above  discussions  really  apply  to  all  fluids  up  to  this 
point.  In  considering  the  problem  of  the  flow  of  air,  however, 
it  must  be  remembered  that  the  velocity  V  will  vary  along  a 
pipe  line,  since  the  pressure  falls  and  the  volume  increases  as 
the  air  passes  along  the  pipe  line.  Hence  the  above  expression 
is  only  true  for  a  differential  length  of  pipe  giving 


The  —  sign  is  used  because  h  falls  as  /  increases. 
MRT 


4 
M  =  pounds  of  air  per  second; 


now 


RT 

i/  MRT  \*dl 


flPRTdl 


]94          ELEMENTS  OF  HEATING  AND   VENTILATION 
If  T  is  assumed  constant  this  integrates  into 


^ 
II2) 


pi  =  the  pressure  at  entrance  in  pounds  per  square  foot; 
p2  =  the  pressure  at  exit  in  pounds  per  square  foot; 
M  =  pounds  of  air  per  second ; 
T  —  absolute  temperature  of  gas; 

1544 

R  —  gas  constant  =  — r— ; r— ; 

mol.  density 

L  =  length  in  feet; 
d=  diameter  in  feet; 

The  above  becomes 

Jipi+P*)  _  f  M2RT  L 

2  I 

pl+p2 

*-  =  mean  pressure. 

pi  —  p2  =  drop  in  pressure. 
Hence 

Drop  in  pressure  in  pounds  per  square  inch 

M2RT    L 

=  f (  I  I  -7  ) 

(n.it)2d'*'b    25. 

where  pm  is  mean  pressure. 

If  pi—p2  is  reduced  to  feet  of  air  at  mean  pressure  this 
formula  reduces  to 

Drop  in  feet  of  gas  at  density  of  mean  pressure 


This  is  the  same  expression  as  that  used  for  liquids  where  the 
specific  volume  does  not  change  for  a  considerable  change  in 
pressure.  In  the  case  of  air  under  pressure  there  may  be  a 


INDIRECT  HEATING  195 

considerable  drop  and  only  Eq.  (in)  or  (113)  may  be  used,  but 
in  cases  where  there  is  little  change  in  pressure  Eq.  (114)  may 
be  used.  This  is  the  same  as  assuming  that  there  is  no  change 
in  velocity.  Then 


The  values  of  /  vary  with  the  velocity  and  the  diameter  of 
the  pipe.  According  to  Weisbach  the  constant  is  0.0193  when 
h  is  in  feet  of  gas,  as  /  and  d  are  in  feet  and  V  is  in  feet  per  second. 


Weisbach  proposes  7=0.0144  H--^-—.    .     .     (116) 


Arson  proposes  7=0.03  +—  —  .....     (IT7) 

Darcy  proposes  the  formula  o.oi  6  +  ~i~    •     •     (n'8) 
and  sometimes  he    ives  this  form 


The  Green  Economizer  Company  gives  values  which   reduce 
this  to 

O.O274   O.OOI45  O.OI20          .    , 

v      d  dv   '  '  ' 


These  formulae  give  curves  shown  in  Fig.  143,  from  which  the 
average  value  is  0.02.  For  brick  or  concrete/  is  increased  about 
50  per  cent.  Formula  115  may  be  used  for  the  flow  of  air  in 
heating  systems,  since  there  is  little  change  in  the  pressure. 

The  loss  in  pressure  due  to  bends  in  pipe  lines  carrying  fluids 
is  usually  expressed  as 


196         ELEMENTS  OF  HEATING  AND  VENTILATION 
Where  K  is  an  experimental  constant; 

hi  =  loss  in  feet  of  head ; 

v  =  velocity  in  feet  per  second; 

The  loss  due  to  obstruction  of  various  kinds,  such  as  valves, 
grills  or  branches  is  given  by  the  same  kind  of  an  expression. 


0.060 


0.055 


0.050 


0.045 


0.040 


0.035 


10 


20  30  40  50 

Velocity  in  Feet  per  Sec. 


FIG.  143.— Values  of  /  by  Arson,  Weisbach  &  Green  Economizer  Co. 

The  values  of  K  used,  as  given  by  the  Green  Fuel  Economizer 
Company  are: 

0.3    for  sharp  bends; 

0.25  for  bends  with  R  =  d\ 

0.15  for  bends  with  R  =  2  to  4^; 

0.07  for  bends  with  R  =  5  to  6d; 

o.oo  for  bends  with  R>6d; 

0.15  for  branches  at  135°; 

1.5    for  grill  or  register,  free  area  =  J  total  area  =  area  of  flue; 

0.75  for  grill,  free  area  =  i|  area  flue. 


INDIRECT  HEATING  197 

At  times  the  expression  for  the  loss  in  bends  is  given  as 


(I22) 


In  which  /  is  given  as  the  length  of  an  equivalent  pipe.  Since 
this  expression  is  similar  to  the  expression  for  the  loss  due  to 
friction  of  straight  pipe,  one  expression  may  be  used  for  both 
if  /  represents  the  length  of  pipe  plus  the  equivalent  length  of 
the  bends. 

N.  S.  Thompson  gives  the  following  equivalent  lengths  of 
bends  in  terms  of  the  diameter  or  widths. 

Radius  of  Quarter  Bend.  Equivalent  Length. 

oD  looD 

ID  6$D 


iD 

i%D  6D 

2D  $D 

For  sudden  enlargement,  if  there  is  little  change  in  pressure  the 
expression  for  loss  is 


Where  vi  is  the  velocity  before  enlargement  while  V2  is  the  velocity 
after  enlargement.  For  contraction  the  velocities  refer  to  that 
in  vena  contracta  after  the  contraction  and  that  in  the  small 
pipe.  These  are  difficult  to  find  and  this  loss  is,  moreover,  very 
small.  The  main  toss  is  in  enlargement  and  this  with  that 
due  to  contraction  may  be  eliminated  by  gradual  changes  in 
section.  From  the  above  it  is  seen  that  the  total  head  causing 
flow  up  to  a  given  point  is 

/   v2  V2  V2        V2 

h=fl  —  +K1—+K2—  +  —.        .     .     .     (124) 

J  d  2g  2g  2g      2g 


198          ELEMENTS   OF  HEATING  AND  VENTILATION 

The  first  term  is  due  to  friction,  the  second  to  a  bend,  the  third 
to  a  grill  or  branch  and  the  last  to  the  velocity.  If  there  is  little 
change  in  temperature  and  pressure  the  following  is  true  approx- 
imately: 

(125) 


Q  =  quantity  per  second  in  cubic  feet; 
fli,  V2j  ^3  =  velocities  at  various  sections  in  feet  per  second; 
Ait  At,  A  3  =  areas  at  various  sections  in  square  feet. 

Since  the  volume  of  a  gas  depends  on  absolute  pressure  and 
temperature  the  change  from  120°  F.  to  110°  F.  would  mean 
a  change  in  the  volume  and  hence  in  the  velocity  of 

459.6+  1  10  _  569.6  _ 
459.6  +  120     579.6 

or  a  difference  of  less  than  2  per  cent;  while  a  change  in  pres- 
sure of  2  ins.  of  water  to  o  in.  would  mean  a  change  of 

408  +  1  _  409 

408  +  2  ~ 


or  about  \  per  cent. 

It  is  seen  then  that  in  most  problems  of  indirect  heating 
the  pressure  and  temperature  changes  are  so  slight  that  for- 
mulae used  for  liquids  may  be  employed  and  hence  the  velocity 
of  any  particular  section  may  be  expressed  in  terms  of  any 
other  section  of  different  size  provided  the  quantity  is  the  same. 
In  most  air  pipes,  however,  the  section  is  only  changed  when  the 
quantity  is  changed.  Hence  in  working  out  the  total  loss  in 
any  system  the  total  loss  may  be  written 


In  this  the  various  losses  are  worked  out  for  their  different 

v2 
velocities  and  the  --is  the  final  velocity  head.     In  this  work 

2g  y 


INDIRECT  HEATING  199 

the  sections  change  so  gradually  that  there  is  no  loss  at  such 
points. 

The  principal  factor  of  the  expression  is  that  due  to  friction 
on  the  side  walls  or 

,     fl  & 

h  =/j  — , 

d  2g' 

since 

MRT    K'M  f 

v  =  — ~7j  =     ,2     for  any  given  condition . 


......     •     •    ,•     (I27) 

or 

M=K"'-~  .  .  .  ..  .....  .  .  (128) 


This  shows  that  the  head  loss  varies  directly  as  the  length  and 
square  of  the  mass  and  inversely  as  the  fifth  power  of  the  diameter, 
or  the  mass  handled  varies  directly  as  the  J  power  of  the  head, 
the  |  power  of  the  diameter  and  inversely  as  the  ^  power  of  the 
length.  These  two  statements  are  important,  as  will  be  seen 
in  laying  out  a  system.  For  instance  if  the  length  of  piping  is 
the  same,  and  the  quantity  is  the  same  the  diameter  of  two 

pipes  will  have  to  be  to  each  other  as  (  —  )     if  there  is  50  per 

cent  more  drop  in  the  first  than  in  the  second.  If  the  drop  and 
length  are  the  same  but  the  quantities  are  as  2  :  i  then  the 
diameter  will  be  as  (2)*  :  i.  These  same  statements  as  to  diam- 
eter may  be  made  of  pipes  of  any  form  if  they  are  geometrically 
similar.  Thus  if  rectangular  pipes  are  always  made  with  a 
given  ratio  between  the  two  dimensions  and  the  smaller  one  is 
called  d  the  expression 


=K.  is  true, 


200         ELEMENTS   OF  HEATING  AND  VENTILATION 

a.oor— 


0.80 


0.60 

3|o 


50.40 


0.20 


Q* 


0.20  0.40  0.60  0.80  1.00 

Values  of  A 


(?i  di 

FIG.  144. — Variation  of  —  for  Different  Values  of   —  for  Same  Friction  Loss 

and  Same  Length. 
1.00 


0.80 


0.60 


* 


0.40 


0.20 


Qi 


0.20  0.40  0.60  0.80  1.90 

Values  of -** 


FIG.   145.— Variation  of  -^  with  Different  Values  of  —  for  Same  Friction  Loss 

V2  /I 

and  Same  Diameter. 


INDIRECT  HEATING  201 

„•*!.   <2± 


Fig.  144,  which  gives  ^  plotted  as  Ij^J  ,  Fig.  145  with  =-,  as 


1.00 


1.00 


^i  /i 

FIG.  146.  —  Variation  of  —  with  Different  Values  of  —  for  Same  Friction  Loss 
d2 

and  Quantity.     (This  curv 
'same  length  and  quantity.) 


and  Quantity.     (This  curve  may  be  used  for  —  for  different  values  of  —  for 

hi  02 


100 


Values' of  r1 

FIG.  147. — Diagram  for  Discharge  from  Pipe. 

(r).  i  and  F*g-  I46>  with  (j"}  plotted  as  fg)    are  of  value  i 
working  out  problems  of  relative  duct  sizes. 


202 


ELEMENTS  OF  HEATING  AND  VENTILATION 


The  further  use  of  this  will  be  explained  later. 

It  may  be  necessary  to  measure  the  quantity  of  air  flowing 
and  to  do  this  there  are  five  general  methods:  first  the  Pitot 
tube,  second  a  standard  orifice,  third  an  anemometer,  fourth  a 
Venturi  meter  and  fifth  an  electric  meter. 

The  Pitot  tube  has  been  described.  By  means  of  this  instru- 
ment the  velocities  at  different  points  in  the  pipe  are  found  and 
if  these  velocities  are  supposed  to  remain  constant  around  any 
given  radius  the  following  expression  will  give  the  quantity  Q: 


Q= 


(129) 


B 


FIG.  148. — Orifices. 


Hence  if  the  values  of  v  be  plotted  as  ordinates  against  the 
values  of  r2  of  the  points  as  abscissae  the  area  of  the  curve, 
Fig.  147,  when  multiplied  by  x  will  give  the  value  of  Q.  In 
measuring  Q  in  this  way  more  readings  should  be  taken  near  the 
edge  of  the  pipe  than  near  the  center. 

In  the  second  method,  that  of  the  standard  orifice,  Fig.  148, 
the  velocity  is  determined  by  the  thermodynamic  equation:  . 


vel.  =  -p'i-tz)  = 

vel.  =  vel.  in  feet  per  second; 
i  =  heat  content  in  B.t.u.; 


INDIRECT  HEATING  203 

p  —  pressure  in  pounds  per  square  foot* 
z>  =  vol.  of  i  Ib.  in  cubic  feet; 

k  =  —  =  i .40  =  ratio  of  specific  heats; 


Now 
Hence 


The  quantity  discharged  in  pounds  per  second  is  given  by 


Q    avel. 

M  =  —  = , 

.V2  V2 

where 

a  =  area  of  orifice ; 


-  •  <*•> 

When  ^2=0.528^  the  maximum  discharge  occurs. 

Fliegner  found  by  experiment  that  ^2=0.5767^1  at  the  point 
of  maximum  discharge,  and  this  as  well  as  the  theoretic  value 
for  maximum  discharge  reduces  Eq.  (131)  to 


where 

M=  pounds  per  second; 
a  =  area  in  square  inches; 
pi  =  pounds^per  square  inch  of  high  pressure 
TI  =  absolute  temperature. 


204 


ELEMENTS  OF  HEATING  AND  VENTILATION 


The  weight  for  any  pressure  p2<o.$pi  is  the  same  as  above, 
so  that  so  long  as  the  pressure  p2  is  below  its  critical  value  the 
discharge  in  pounds  is  a  fixed  quantity  and  independent  of  pz* 
Above  this  critical  value  the  discharge  does  depend  on  p2. 

Fliegner  gives  this  equation  in  the  form, 


M  =  i  .o6oa 


x/' 


(i33) 


This  equation  is  for  a  rounded  orifice.  For  a  sharp-edged 
orifice  in  a  thin  plate  a  constant  of  0.62  is  used,  by  which  to 
multiply  the  theoretic  discharge.  The  constant  is  about  0.83 
for  short  tubes  and  0.92  when  these  are  rounded  at  entrance. 

The  anemometer,  Fig.  149,  is  only  of  value  when  the  velocity 
is  not  over  1200  to  1500  ft.  per  minute  and  hence  it  is  used  often 

in  heating  work  where  these 
velocities  are  found.  The  in- 
strument is  checked  by  re- 
volving it  on  a  long  arm  and 
noting  the  distance  moved  and 
that  recorded.  In  this  way 
the  instrument  is  calibrated. 
In  using  this  apparatus  the 
readings  may  be  plotted  as 
velocities  on  a  diagram  similar 
to  that  used  with  the  Pitot 

FIG.  HQ.-Anemometer.  tube    Or    the    area    °f    a  P1?6 

or  duct  may  be  divided  into 

square  areas  by  imaginary  lines  and  the  velocity  determined  in 
each  of  them.  The  average  of  these  will  give  the  average 
velocity.  Another  method  is  to  gradually  move  the  anemometer 
over  the  area  of  the  duct  or  pipe  covering  the  whole  pipe  in  this 
way  and  the  recorded  amount  per  minute  will  give  the  average 
velocity. 

The  Venturi  meter,  Fig.  150,  consists  of  a  converging  and 
diverging  section  of  pipe.  The  diverging  section  is  more  grad- 
ual on  account  of  the  loss  due  to  enlargement  being  greater 
than  that  due  to  contraction. 


INDIRECT  HEATING 


205 


By  equating  the  sum  of  the  energies  at  the  large  and  small 
sections  and  remembering  that  the  expansion  is  adiabatic  the 
formula  for  the  discharge  may  be  derived.  Thus: 

vel.22 


a\  vel.  i     #2  vel.2 


k 

iPl1 


vel.i2[7aifl2\2      1 

— Lfe )  -1]; 


vel.i  = 


vel. 


(134) 
(135) 


FIG.  150. — Venturi  Meter. 

pi  =  pressure  in  pounds  per  square  foot  at  section  i ; 
p2  =  pressure  in  pounds  per  square  foot  at  section  2; 
D!  =  specific  volume  in  cubic  feet; 
V2  =  specific  volume  in  cubic  feet; 
k  =  ratio  of  specific  heats; 
vel.i  =  velocity  in  feet  per  second; 
a  =  area  in  square  feet; 
g  =  acceleration  of  gravity; 
per  second. 


206          ELEMENTS  OF  HEATING  AND  VENTILATION 

The  methods  thus  used  are  applicable  under  different  con- 
ditions. The  anemometer  is  applicable  to  low  velocities  up  to 
1500  ft.  per  minute,  the  Pi  tot  tube  to  velocities  of  2400  to  7000 
ft.  per  minute,  and  the  standard  orifice  to  higher  velocities  when 
the  pressure  drop  is  considerable.  The  Venturi  meter  is  applic- 
able to  steady  flow  of  all  velocities. 

A  recent  method  used  by  Prof.  C.  Thomas  consists  in 
heating  gas  by  a  known  amount  of  electrical  energy  and  then 
by  the  rise  in  temperature  finding  the  mass  of  gas,  and  from 
it  the  volume  and  thus  the  velocity. 


Volts  X  amp.     42.42 

746  60        1/r 

-^— v =M 


M  =  mass  of  air  per  second; 
volts  =  average  voltage ; 
amp.  =  average  current; 

/2  =  temperature  of  outlet; 

t\  =  temperature  of  inlet; 


MRT 
vol.  = 


vol. 

—  =  velocity, 
area  J 


If  the  head  lost  is  h  ft.  of  air  the  work  required  to  overcome 
this  per  second  if  Q  cu.it.  per  second  are  discharged  and  each 
cubic  foot  weighs  w  Ibs.  is 


work  per  second  =  whQ  =  -hQ     .     .    .     (137) 


INDIRECT  HEATING  207 

The  formulae  may  now  be  applied  for  the  following  tables: 

TABLES   TO    BE   USED    IN   DESIGN   WORK 

PRESSURES  AND  VELOCITIES  or  AIR  AT  70°  F. 


Inches 

Water. 

Ounces 
Pressure. 

Velocity, 
Feet  per 
Second. 

Inches 
Water. 

Ounces 
Pressure. 

Velocity, 
Feet  per 
Second. 

Inches 
Water. 

Ounces 
Pressure. 

Velocity 
Feet  per 
Second. 

A 

0.04 

I6.7 

A 

0.25 

44-2 

if 

I  .OI 

89 

i 

O.oy 

23-6 

i 

0.29 

47-3 

2 

I.I6 

95 

A 

O.  II 

28.9 

i 

0.36 

52-8 

3 

1-73 

116 

i 

4 

0.14 

33-4 

i 

0-43 

57-9 

4 

2.31 

134 

A 

0.18 

37-3 

i 

0.51 

60.7 

6 

3-47 

167 

I 

O.  22 

40.9 

I 

0.58 

66.9 

8 

4-63 

189 

ii 

0.72 

74-9 

12 

6.94 

232 

i| 

0.87 

82.0 

16 

9-25 

368 

DIAMETER  OF  PIPES  FOR  VARIOUS  CAPACITIES  AND  VELOCITIES 


Cubic 

??et  of        500 
Air  per 

Minute. 

600 

700 

850 

IOOO 

1200 

1400 

1700 

2000 

2500 

200       8.6 

7-83 

7.2 

6.6 

6.0 

5-5 

5-i 

4-7 

4-3 

3-9 

400        12.2 

ii.  i 

10.3 

9-3 

8.6 

7-8 

7-3 

6.6 

6.1 

5-5 

700 

16.0 

i5-i 

13-6 

12.3 

n-3 

10.4 

9.6 

8.8 

8.1 

7-2 

1000 

19-3 

17-5 

16.2 

14.8 

13-5 

12.4 

n-5 

10.5 

9.6 

8.6 

1500 

23-5 

21.4 

19.9 

18.0 

16.6 

15.2 

14.1 

12.8 

n.  8 

10.5 

2OOO 

27.1 

24-7 

22.9 

20.8 

19.2 

17.9 

16.2 

14.8 

13-6 

12.2 

3000 

33-2 

30-3 

28.0 

25.5 

23-5 

21.4 

19.9 

18.1 

16.7 

14.9 

4OOO 

39-3 

35-o 

32-4 

29.4 

27.1 

24.7 

23.0 

20.8 

19.2 

17.2 

5000 

42.8 

39-2 

36-3 

32.9 

30.3 

27.8 

25-5 

23-3 

21-5 

19.2 

7500 

52-5 

47-9 

44-3 

4O-.  2 

35-8 

34-0 

3i-5 

28.7 

26.3 

23-5 

IOOOO 

61.0 

55-3 

51.2 

46.6 

42.8 

39-2 

36.3 

32-9 

30.4 

27.2 

15000 

74-2 

67.8 

62.9 

57-o 

52.5 

47-9 

43-9 

40.3 

37-i 

33-2 

2OOOO 

85.6 

78.3 

72-3 

65-7 

60.0 

55-4 

51-2 

46.4 

42.9 

38.4 

30000 

105.0 

95-8 

88.6 

80.5 

74.2 

67.7 

62.7 

57-o 

52.6 

47-0 

40000 

121  .O 

in  .0 

103.0 

92.9 

86.0 

78.1 

72-3 

65-7 

60.6 

54-2 

50000 

135-0 

124.0 

115.0 

105.0 

95-8 

87.8 

81.3 

73-6 

68.0 

60.7 

62500 

I5O.O 

138.0 

129.0 

115.0 

107.0 

98.0 

91.0 

82.3 

75-9 

67.8 

75000 

166.0 

151.0 

140.0 

127.0 

117.0 

108.0 

IOO.O 

90.2 

83-0 

74.2 

I  00000 

193.0 

i75-o 

162.0 

148.0 

i35-o 

124.0 

115.0 

105.0 

96.0 

85.8 

208 


ELEMENTS  OF  HEATING  AND  VENTILATION 


DIAMETERS  OF 
CIRCULAR  AREAS  EQUIVALENT  TO  RECTANGULAR  DUCTS  IN  CARRYING  CAPACITY 


Width. 

Length 

3 

4 

6 

9 

12 

IS 

18 

21 

24 

30 

36 

3 

3-7 

4 

3-9 

4-4 

6 

4.6 

5-4 

6.7 

9 

5-6 

6.6 

8.1 

IO.O 

12 

6-3 

7-4 

9.2 

".  5 

13.3 

IS 

7.0 

8-3 

10.3 

12.7 

14.7 

I6.S 

18 

7-6 

8.9 

II  .2 

13.9 

16.2 

18.1 

19.7 

21 

8.1 

9-5 

12.  O 

15.0 

17.5 

i9-5 

20.4 

23-6 

24 

8-5 

IO.O 

12.7 

15.8 

18.4 

20.8 

22.9 

24.7 

26.4 

30 

9-4 

ii  .1 

I4.O 

17.5 

20.5 

23.1 

25-5 

27.6 

29-5 

33-0 

36 

IO.I 

ii.  9 

15-2 

19.1 

22.2 

25.2 

27.8 

30.0 

32.3 

36.4 

39-9 

The  loss  in  inches  of  water  in  100  ft.  of  i2-in.  pipe  at  various 
velocities  is  given  in  the  table  below  as  well  as  the  horse-power. 

To  use  this  table  for  any  other  diameter  or  length  the  values 
are  multiplied  by  one  one-hundredths  of  the  length  and  divided 
by  one-twelfth  of  the  diameter  for  loss  of  head,  while  for  horse- 
powers the  tabular  values  are  multiplied  by  the  two  factors. 
Thus  for  2000  ft.  per  minute  in  75  ft.  of  8-in.  pipe 


H.P.  =  0.1260  X—  X—  =0.0634. 
100     12 


FRICTION  LOSS  AND   H.P.  PER  100    FEET    OF    12-INCH   PIPE 


Velocity. 

Friction, 
Inches,  Water. 

H.P. 

Velocity. 

Friction, 
Inches,  Water. 

H.P. 

200 

0.005 

0.0002 

1  200 

0.184 

0.0270 

400 

O.O2I 

O.OOII 

1500 

0.288 

0.0536 

600 

0.046 

0.0035 

2OOO 

0.510 

o.  1269 

800 

0.082 

0.0082 

3000 

1.150 

0.4284 

IOOO 

0.128 

0.0159 

4OOO 

2.050 

1-0153 

This  table  for  friction  loss  holds  for  i2-in.  square  pipe. 
To  show  the  effect  of  temperature  on  the  various  quantities 
the  following  table  is  given: 


INDIRECT  HEATING 
EFFECT  OF   TEMPERATURE  ON  AIR   PROBLEMS 


209 


Tempera- 
ture, 
Degrees  F. 

Relative 
Pressure  for 
Same  Head 
of  Air. 

Relative 
Velocity  for 
Same 
Ounce 
Pressure. 

Relative 
Weight  for 
Same 
Volume. 

Relative 
Volume  for 
Same 
Weight. 

Relative 
Power  for 
Same 
Velocity. 

Relative 
Power  for 
Same 
Weight. 

2O 

.  IO 

0-95 

.10 

0.91 

.  IO 

0.83 

30 

.08 

0.96 

.08 

0-93 

.08 

0.87 

40 

.06 

0.97 

.06 

0.94 

.06 

0.89 

SO 

.04 

0.98 

.04 

0.96 

.04 

0.92 

60 

.02 

0.99 

.02 

0.98 

.02 

0.96 

70 

.OO 

I  .OO 

.00 

.00 

.OO 

.00 

80 

0.98 

I  .OI 

0.98 

.02 

0.98 

.04 

90 

0.96 

1  .02 

0.96 

.04 

0.96 

.08 

IOO 

0-95 

1.03 

o-95 

•05 

o-95 

.10 

no 

0-93 

1  .04 

0-93 

.07 

0-93 

.14 

120 

0.92 

1-05 

0.92 

.09 

0.92 

.18 

130 

0.90 

1.  06 

0.90 

.11 

0.90 

•  23 

140 

0.88 

1.  06 

0.88 

•  13 

0.88 

.28 

150 

0.87 

1.07 

0.87 

.15 

0.87 

•  32 

2OO 

0.80 

I.  II 

0.80 

.25 

0.80 

-56 

250 

0-75 

1.16 

0-75 

•33 

o.75 

.78 

400 

0.62 

1.27 

0.62 

.61 

0.62 

2.60 

600 

0.50 

1.41 

0.50 

2.OO 

0.50 

4.00 

The  data  for  the  losses  in  pipes  being  known  it  now  becomes 
necessary  to  outline  the  method  of  procedure  for  a  given  plant. 

Register  Faces.  The  register  faces  should  be  large  enough 
to  give  a  velocity  of  300  to  550  ft.  per  minute  when  in  the  wall, 
while  200  to  250  is  the  value  to  be  used  for  floor  registers.  These 
must  be  selected  so  that  there  is  no  annoyance  to  the  occupants 
of  the  room.  The  net  area  of  the  register  is  usually  66  per  cent 
of  the  area  of  the  opening  in  the  end  of  the  duct  while  there  is 
a  border  of  about  2  ins.  around  this.  A  10  by  10  opening 
would  give  a  net  register  area  of  66  sq.in.  and  would  have  an 
extreme  register  face  area  of  about  144  sq.in. 

As  a  guide  the  following  table  of  velocities  has  been  com- 
puted from  data  given  in  Loomis'  Meteorology  by  Carpenter: 


Just  perceptible 
Gently  pleasant 
Pleasant*brisk 
Very  brisk 


175  ft.  per  minute. 
330       w        " 

I IOO          "  " 

2200  "  " 


210          ELEMENTS  OF  HEATING  AND  VENTILATION 

High  wind  3100  ft.  per  minute. 

Very  high  wind      4000       '  ' 
Strong  gale  5000       '  ' 

Flues  and  Ducts.  After  the  registers  the  flues  may  be  chosen 
with  velocities  of  500  to  750  and  finally  the  horizontal  flues  with 
800  to  1  200  ft.  per  minute.  In  any  case  low  velocities  are  of 
value,  as  the  loss  depends  on  the  square  of  the  velocity,  and  the 
only  limit  is  the  cost  of  the  ducts  and  the  space  available  for 
them.  Of  course  for  lack  of  space  it  may  be  necessary  to  increase 
the  velocities.  The  high  velocities  are  limited  by  noise.  The 
values  given  above  will  give  a  quiet  system. 

To  get  the  size  of  the  ducts  it  is  well  to  lay  out  the  system 
as  shown  in  Figs.  136,  137,  assuming  the  velocities  to  one  of 
the  rooms,  usually  the  most  remote,  and  from  that  work  out 
the  other  circuits. 

In  Fig.  136  a  double-duct  system  is  assumed  in  which  one- 
half  of  the  air  is  hot  and  one-half  tempered.  Assuming  the 
velocity  in  the  various  parts  of  the  system  to  room  18,  above 
room  12,  the  pressures  are  found  at  the  various  points.  These 
calculations  are  now  given. 

Pressure  in  rooms  =  /?«,; 
Velocity  at  register  =  300  ft.  per  min.  =  5  ft.  per  sec. 

88000 
Area  register  =  =  4.  9  sq.ft.; 


Velocity  head  =  7  —  =  0.4  ft.  air  =  0.005  in.  water; 
°4-3 

Velocity  in  flue  =  600  ; 

Area  of  flue  =  -  —    —r-  =  2.4  sq.ft.  ; 
600X60 

Loss  in  brick  flue  with  2  bends  =  (  2X0.25+—  —  *-  ji&Z  —  = 

(•SH~*5)<  —  =  2.8  ft.  of  air  =  0.04  in.  water. 
°4-3 


INDIRECT  HEATING  211 

Velocity  in  ducts  1 200  ft.  per  minute. 

151000 
Area  of  tempered  ducts  froo  A  to  B  =  12QO x6o  =  2<1  scl-*t<; 

(assuming  50,000  cu.ft.  per  room) 

302000 

From  B  to  C  =  —      ...    =4.2  sq.ft. 
1 200  X  60 

004000 

From  C  to  heater  —,-  =  12.6  sq.ft. 

1200X60 

Area  of  hot  ducts  at  98°  F. 

From  A  to  B  =  2.i  X  1.05    =2.2. 
From  B  to  C  =  4.2X  1.05    =4.4. 
From  C  to  heater  =  12. 6X1.05  =  13. 2. 

Losses : 

Tempered  A  to  B  [12X24"]. 

2  2  2O2 

(0.02  X— +3X0.25)— =12'  of  air. 
Tempered  B  to  C  [12X48"]. 

/  32\  202 

I  0.02  X —  17 —  =  10  of  air. 
V  0.4/64.3 

Tempered  C  to  fan  [30X63"]. 

28  .    202 

(0.02  X— ^-+2X0.25)7 —  =  8.5   of  air. 
0.05  04.3 

The  pressure  heads  for  the  hot  air  in  feet  of  air  will  be  the 
same,  although  when  reduced  to  oz.  pressure  they  will  amount 
to  4  per  cent  less  on  account  of  the  higher  temperature  of  air. 
This  decrease  will  be  used,  however,  in  the  heating  coils  over 
which  the  hot  air  will  flow  so  that  the  resistance  is  the  same  in 
each  duct. 

The  flues  now  leading  from  A  to  second  floor  and  from  A 


212          ELEMENTS  OF  HEATING  AND  VENTILATION 

to  first  floor  have  to  be  so  designed  that  they  will  give  the  proper 
discharge,  for  although  there  is  the  same  drop  in  each  of  them 
the  lengths  are  different  and  hence  to  get  the  proper  quantity, 
the  area  of  the  flues  leading  to  the  lower  floors  is  smaller.  The 
quantities  are  the  same  for  this  same  drop,  hence 

L      Li 


D      n/ZlV 
Dl'D(j:) 

Dl  =  1.32. 


(ij  is  assumed  as  D\  in  getting  the  equivalent  length  for  the 
quarter  bends.) 


To  get  the  size  of  the  flues  at  C  it  must  be  remembered  that 
the  quantity  is  the  same  as  before,  but  the  pressure  drop  is 
greater  since  the  pressure  in  the  rooms  is  the  same  while  the 
pressures  at  the  bases  of  the  flues  are  different. 


h  for  flues  at  A  =2.8  iL  a.l; 
h  for  flues  at  C  =  2.8  +  12  +  10  =  24.  8  ft.  air. 


24. 


INDIRECT  HEATING 


213 


To  aid  in  problems  of  this  kind  Figs.  144-146  have  been  added, 
giving  the  ratios  of  Qs,  ls,  ds. 


FIG.  151. — Double  Dust  Dampers. 


1    , 

-^\ 

j    1 

L-iiJ 

-•""  3 

: 

j—  1-1-1  1 
!   '  1  1 

!—{{=« 

{ 

J—  i 

Off 

i  —  -UJ 

\ 

j 

i   l!i 

m, 

/    ^~ 

"N 

r— T-- 


Hot  Air 


FIG.  152. — Single  Duct  System. 

In  many  cases  the  flues  are  all  made  of  the  same  size  and  in 
addition  to  the  mixing  damper  A,  shown  in  Fig.  151,  there  are 
a  pair  of  dampers,  B,  shown  in  the  figure,  which  may  be  locked 


214          ELEMENTS  OF  HEATING  AND  VENTILATION 

in  any  position,  thus  checking  the  flow  in  any  room  and  equaliz- 
ing the  discharge. 

If  the  job  is  equipped  with  single  ducts,  as  shown  in  Fig. 
153,  then  one  duct  is  computed,  for  instance  that  to  room  18, 
with  a  velocity  of  840  ft.  per  minute,  and  then  since  the  pressure 


1  713 


2814 


FIG.  153.—  Single  Ducts  for  School  No.  3. 

drop  to  each  room  is  the  same  with  practically  the  same  quantity, 
the  sizes  of  others  are  given  by 


Now  the  size  of  duct  to  room  18  is 
88200 


r     ^(46+30x1})  ,  0.03  x  (38  +25)1  142 

Loss  =  [0.02  X-     —  —       -J  —  -35'  of  air. 

For  room  12 

h  _o.Q2(48+38)  +0.03(38  +  25) 
fa     0.02(46+38)  +0.03(25  +  25)' 

Using  this  the  size  of  flue  and  duct  are  found.  Fig.  152 
shows  the  mixing  dampers  used  in  the  single-duct  method  with 
the  control  damper  for  discharge. 

Loss  of  Pressure  in  Heaters.  The  losses  in  the  various 
heaters  have  been  found  by  the  manufacturers  and  some  are 
given  in  the  tables  below: 


INDIRECT  HEATING 


215 


LOSS  IN  PRESSURE  IN   BUFFALO  HEATERS 


Velocity  through  Clear 
Area  in  Feet  per  Minute. 

Loss  in  Ounces  per  Square 
Inch  per  Section  of  4  Rows. 

Loss  in  Inches  of  Water  per 
Section  of  4  Rows. 

700 

0.027 

0.047 

800 

0-035 

O.o6l 

QOO 

0.045 

0.078 

IOOO 

0-055 

0.095 

IIOO 

0.067 

0.116 

I2OO 

0.080 

0.138 

1300 

0.093 

o.  162 

I4OO 

o.  104 

0.180 

1500 

0.127 

O.  22O 

The   pressure-loss   in   heaters   should   not   exceed   one-half 
total  loss  in  head. 

LOSS  IN  PRESSURE  IN  GREEN    POSITIVFLO  HEATERS  WITH 
PIPES  ON  2f"  CENTERS 


Loss  in  Inches  of  Water. 

Air 

Velocity  in 

Feet  per 

Minute. 

4  Rows. 

8  Rows. 

12  Rows. 

16  Rows. 

20  Rows. 

24  Rows. 

600 

0.04 

O.o6 

0.09 

O.I2 

0.14 

0.15 

800 

O.o6 

O.IO 

0.15 

0.19 

0.23 

0.26 

IOOO 

0.09 

0.15 

0.23 

0.30 

0.37 

0.41 

1200 

O.  12 

O.2I 

0.31 

0.43 

0.56 

0.58 

I4OO 

0.17 

0.30 

0.45 

0.60 

0.75 

0.90 

I600 

O.2O 

0.34 

0.52 

0.69 

0.86 

1.03 

Free  air  space 


Lineal  feet  of  pipe 


8. 4 X rows  of  pipe' 
LOSS  IN  PRESSURE  IN  VENTO  HEATERS   IN   INCHES  OF  WATER 


Velocity 
through  Clear 
Area  in  Feet 
per  Minute. 

i  Section. 

2  Section. 

3  Section. 

n  Sections. 

400 

0.015 

O.OlS 

0.018 

0.018+0.  OOS(»  —  2) 

600 

0.033 

0.041 

0.058 

o  .  041  +o  .  01  75(w  —  2) 

800 

0.059 

0.072 

o.  104 

0.0724-0.032(^  —  2) 

IOOO 

0.092 

0.  112 

o.  162 

0.112+0.050(^  —  2) 

I2OO 

0-133 

o.  162 

0.234 

o.  1  62  +0.07  2(71  —  2) 

1400 

0.180 

O.  22O 

0.318 

0.220+0.  098(7*  —  2) 

I6OO 

0.236 

0.288 

0.416 

0.  288  +  0.  I28(»  —  2) 

216 


ELEMENTS   OF  HEATING  AND  VENTILATION 


Fans.  There  are  several  forms  of  fans  used  for  mechanical 
ventilation.  The  plate  fan  used  for  many  years  consists  of  a 
wheel  with  a  number  of  radial  paddles  or  vanes,  Fig.  154  A,  or  a 
number  of  curved  vanes,  Fig.  154  B,  enclosed  in  a  metal  casing. 
These  were  used  for  many  years  and  in  1897  Mr.  S.  C.  Davidson 
of  Belfast,  Ireland,  invented  a  curved  vane  wheel  in  which  the 


FIG.  154. — Radial  Vanes  on  Standard  Form  of  Fan.     Curved  Vanes  on  I-Beam 

Wheel. 


FIG.  155. — Sirocco  Fan. 


FIG.  156. — Conoidal  Fan. 


blades  were  not  so  deep,  Fig.  155,  which  he  called  the  sirocco 
fan.  This  has  been  followed  by  the  conoidal  fans  of  the  Buffalo 
Forge  Company,  Fig.  156.  These  are  all  used  for  forcing  air. 
The  cone  wheel,  Fig.  157,  is  used  mainly  on  the  vacuum  system 
for  sucking  air  from  a  given  space.  The  cone  center  serves 
to  guide  the  air  from  the  center.  The  propellor  or  disc  fan, 
Fig.  157,  is  used  to  exhaust  air  from  a  room.  It  is  usually 


INDIRECT  HEATING 


217 


placed  in  the  partition  or  wall  of  the  room  from  which  it  draws 
vitiated  air  and  delivers  it  to  the  atmosphere. 

Fans  are  made  with  discharges  in  different  directions  and  at 
times  they  may  have  more  than  one  outlet.  In  Fig.  159 
different  arrangements  are  shown.  A  represents  a  full  housing 
top  horizontal  discharge,  B  is  a  full-housed  top  vertical  dis- 
charge, C  is  a  three-quarter-housed  bottom  angular  discharge, 
D,  a  three-quarter-housed  top  angular  discharge  and  F  a  full- 
housed  multiple  discharge  fan.  E  represents  a  full-housed 
bottom  vertical  discharge.  Fans  are  made  either  full  or  three- 


FIG.  157. — Cone  Wheel. 


FIG.  158.— Ventilator. 


quarter  housed  with  any  methods  of  discharge  to  suit  conditions. 
They  are  driven  by  direct-connected  motors  or  engines  or  they 
may  be  belted  to  a  prime  mover. 

The  manufacturers  call  a  fan  right  or  left  if  on  facing  the 
pulley  side  of  the  fan  .the  discharge  is  to  the  right  or  left. 

Fans  of  the  type  shown  in  Fig.  154  are  usually  designed 
so  that  the  peripheral  speed  of  the  fan  wheel  is  equal  to  that 
produced  by  the  dynamic  pressure  at  the  point  of  maximum 
efficiency.  At  this  point  the  static  pressure  is  equal  to  about  75 
per  cent  of  the  dynamic  pressure  while  the  velocity  head  is  about 
25  per  cent  of  the  pressure.  As  the  resistance  is  decreased  the 
cubic  feet  delivery  is  increased  and  the  total  pressure  falls  until, 


218          ELEMENTS  OF  HEATING  AND  VENTILATION 

when  there  is  no  resistance  around  the  fan,  free  discharge  occurs 
with  total  zero  pressure  head,  50  per  cent  of  the  total  head  at 
best  efficiency.  This  is  all  velocity  head.  The  discharge  at 


FIG.  159. — Forms  of  Housings. 

this  time  is  145  per  cent  of  the  discharge  at  the  best  point.  If 
on  the  other  hand  the  discharge  is  closed  off  the  static  head 
increases  until  it  equals  the  total  pressure  at  zero  discharge. 


INDIRECT  HEATING 


219 


At  this  point  the  pressure  is  116  per  cent  of  that  due  to  a  velocity 
equal  to  the  peripheral  speed  of  the  wheel.  The  curve  for  the 
Buffalo  Forge  Company  fans  showing  this  change  in  pressure 
as  the  discharge  is  throttled  is  given  in  Fig.  160.  This  curve 
has  been  prepared  from  one  given  by  the  company  from  results 
of  tests. 

If  in  any  case  the  resistance  in  the  flues,  ducts,  heaters  and 


§ 


cy 

8 


8 


\ 


£ 


0 


20 


40  60  80  100  120 

Percentage  of  Volume  at  Best  Efficiency 


140 


FIG.  1 60. — Relation  between  Pressure  and  Volume  in  Percentage  of  the  Pressure 
and  Volume  from  Fan  at  Maximum  Efficiency  as  Given  by  Curves  of  the 
Buffalo  Forge  Co. 

casing  amounts  to  hiw  of  water,  this  quantity  represents  75 
per  cent  of  the  total  head  produced  by  the  wheel,  which  is  equal 
to  the  velocity  head  of  the  peripheral  speed. 


1.728 

Po 

°-75 


=  P     (Total  pressure).     .     .     .     (139) 


220          ELEMENTS  OF  HEATING  AND  VENTILATION 

r^n~ 
Peripheral  velocity  of  wheel  =  66.9^1 — — (101) 


75 

\ 

(140) 


-•4s 

60 

where  d  =  diameter  of  wheel  in  feet,  Ar  =  R.P.M.  Having  the 
peripheral  speed  of  the  wheel,  the  diameter  and  number  of 
revolutions  must  be  found.  This  is  determined  by  the  square 
inches  of  blast  area  or  "  blast." 

This  area  is  that  through  which  the  fan  will  discharge  and 
give  a  velocity  equal  to  the  peripheral  velocity  of  the  wheel. 

In  most  plate  fans  it  is  equal  to  -  -  where  w  is  the  width  of 

o 

the  blade  at  the  tip,  and  d  is  the  diameter.  Now  if  Q  is  the 
cubic  feet  discharged  per  second,  and  vp  is  the  peripheral  speed 
of  the  wheel  in  feet  per  second,  the  area  of  blast  is 

Q    wd 


Since  w  is  made  equal  to  o.^d,  while  the  widest  part  is 
the  value  of  a  becomes 


0.4^2 

a  =  —   — 
o 


Hence 


and  d  may  be  found  and  then  N.  The  width  at  body  and  tip 
are  also  known.  With  high  pressures  and  small  quantities  the 
width  is  made  smaller  than  0.5^,  while  for  large  quantities  under 
small  heads  the  width  is  made  large. 


INDIRECT  HEATING 

The  inlet  area  in  square  feet  is  given  by  Parsons  as 
0.00054(3 


221 


Outlet  area  is  given  by 

.4  out  =1.0  to  1.25  inlet  area,  or  this  may  be  calculated  with 
the  flues  and  ducts. 

The  radial  depth  of  the  blade  near  the  edge  is  about  0.15/7, 
although  another  way  would  be  to  have  the  corner  A,  Fig.  161, 
fit  J  in.  within  the  inlet  opening  with  a  clearance  of  about 


FIG.  161. — Approximate  Wheel  Dimensions. 

|  in.  from  the  casing.  This  with  the  outer  diameter  will  fix  the 
radial  depth. 

The  power  generated  by  a  fan  consists  of  three  parts:  (a) 
that  required  to  give  the  air  velocity,  (b)  that  required  to 
change  the  intrinsic  energy,  and  (c)  that  to  do  the  external  work. 

The  first  amount  is  given  by 

Work  per  second  =  M—  =  MK2—. 

2  CT  2P 

M =mass  per  second, 

v  =  velocity  of  discharge  in  feet  per  second; 
V  =  peripheral  velocity  of  fan ; 
K=  percentage  factor. 


ELEMENTS  OF  HEATING  AND  VENTILATION 
The  second  item  is  given  by 

Work  per  second  =  M\ — -  —  —  — ~1.     .     .     (142) 
10.405     0.405  J 

po,  p^  the  pressure  per  square  foot  at  outlet,  inlet,  in 

pounds. 
v0,  Vt,  the  volumes  of  one  pound  of  air  in  cubic  feet. 

The  third  amount  is  given  by 

Work  per  second  =  M[p0v0—pivb   •     •     •     (143) 
The  sum  of  these  is  equal  to  the  total  work. 

Work  per  second  =  M  -  — \-~^  - — -£-• — \-p0v0—p^i 

\  *- 1         /v       I          K       I  J 


but 

M  =  aV  „,„     and    v  = 
Therefore 


Eq.  (145)  may  be  simplified  by  assuming  that  the  intrinsic 
energy  is  not  altered  and  that  the  specific  volume  does  not 
change  during  the  small  change  in  pressure.  This  gives 


(146) 


H  =  total  or  dynamic  head. 


INDIRECT  HEATiNG  223 

Now 

V2 
#is-.      •;.    •    ....     (i47) 

.'.    Work  per  second  =  -^  —  =K1V3.  .    ...     (148) 

K-l-  o  2g 


(149) 


From  Eqs.  (147)  (148)  and  (149)  the  important  relations, 
that  Q  varies  as  V,  H  as  V2  and  work  per  second  or  power,  as 
F3,  are  seen.  These  relations  are  shown  by  test  data  and  by  the 
tables  which  follow.  These  are  prepared  from  the  catalogues 
of  the  manufacturers.  Only  a  few  values  are  given,  but  in  any 
case  the  relation  can  be  used  to  find  the  results  under  different 
conditions. 

Thus  from  the  table  it  is  seen  that  as  the  diameter  of  the 
wheel  increases,  the  number  of  revolutions  per  minute  to  pro- 
duce a  given  pressure  will  decrease,  the  product  of  speed  and 
diameter  being  constant.  The  blast  area  varies  as  the  square 
of  the  diameter,  and  since  in  any  column  the  velocity  is  constant, 
the  quantity  discharged  will  vary  as  the  square  of  the  diameter. 
The  velocity  being  constant  and  the  quantity  varying  as  the 
square  will  make  the  power  vary  as  the  square  of  the  wheel 
diameter  in  any  column  of  equal  pressure.  To  care  for  differences 
in  pressure,  it  will  be  remembered  that  pressure  varies  as  the 
square  of  the  velocity  and  hence  the  speed  of  a  given  wheel 
.will  vary  as  the  square  root  of  the  pressure,  and  the  power  will 
vary  as  the  three  halves  power,  while  the  quantity  will  vary 
as  the  speed  or  the  square  root  of  the  pressure. 

Thus  i  oz.  pressure  with  a  wheel  22  ins.  in  diameter  requires 
896  R.P.M.  with  a  discharge  of  2116  cu.ft.  and  1.07  H.P.  A 

36-in.  wheel  will  run  at  -7X896  or  548  R.P.M.     It  will  dis- 

(A\  2 
—  j   or  5630   cu.ft.  if  the  same  proportions  for 

width  are  used,  while  if  these  are  changed  the  result  will  be 


224          ELEMENTS  OF.  HEATING  AND  VENTILATION 

different.  In  some  tables  it  is  seen  that  the  discharges  are  not 
so  proportioned  and  this  means  a  change  in  the  proportion  of 
the  width. 

The  power  required  will  vary  as  the  quantity,  since  the 
pressure  is  the  same 


For  2  oz.  pressure  for  a  22-in.  wheel  the  following  should  be 
found  : 


^  =  2^X2116  =  2980; 
H.P.  =  2*Xi.oy  =  3.00. 

In  this  way  new  columns  may  be  made  for  the  table  or 
the  data  for  different  conditions  of  flow  may  be  found.  If 
reference  is  made  to  the  curve  of  Fig.  160,  the  effect  of  chang- 
ing the  pressure  from  that  for  which  the  table  is  built  is 
seen. 

Before  quoting  the  tables  of  the  manufacturers  of  fans  it 
is  well  to  note  the  results  obtained  from  the  Sirocco  fan,  in 
which  shallow  blades  are  used.  This  fan  gives  higher  dynamic 
pressures  than  the  peripheral  speed  of  the  wheel.  This  is  due 
to  the  better  action  of  properly  shaped  blades  and  to  the  fact 
that  there  is  less  friction.  The  space  taken  by  the  fan  is  less 
than  that  required  for  other  types,  also  the  power  is  less.  The 
makers  claim  a  saving  of  |  the  space,  J  the  weight  and  f  the 
power.  However,  for  this  fan  the  same  variations  of  power, 
capacity,  speed  and  pressure  as  before  noted  is  to  be  found  in 
the  tables. 

It  rarely  happens  that  the  engineer  designs  his  fan.  By  an 
understanding  of  the  table  the  proper  size  may  be  selected. 

The  following  tables  do  not  give  all  sizes  made,  but  refer- 
ence to  the  catalogues  of  builders  is  recommended  for  closer 
figures.  The  discharge  is  in  cubic  feet  per  minute. 


INDIRECT  HEATING 


225 


SIROCCO  FAN. 

BUFFALO  FORGE  FAN. 

Fan 
No. 

Diam. 
Wheel. 

Total  Dynamic 
Pressure. 
Oz. 

Fan 

No. 

30 

Diam. 
Wheel. 

Total  Dynamic 
Pressure. 
Oz. 

i 

i 

2 

\ 

i 

2 

I 

6" 

Cu.ft. 
R.P.M. 
B.H.P. 

155 
1145 
0.0185 

3io 
2290 
0.147 

440 
3230 
0.42 

22" 

Cu.ft. 
R.P.M. 
B.H.P. 

1497 
634 
0.37 

2116 
896 
1.07 

2989 
1264 

2-94 

1} 

9" 

Cu.ft. 
R.P.M. 
B.H.P. 

350 
762 
0.042 

700 
1524 
0.333 

IOOO 

2152 
0.95 

45 
70 

s*r 

Cu.ft. 
R.P.M. 
B.H.P. 

3292 
430 
0.81 

4640 
607 
2.30 

6550 
857 
6.49 

2 

12" 

Cu.ft. 
R.P.M. 
B.H.P. 

625 
572 
0.074 

1250 
H45 
0.588 

1770 
1615 
1.66 

so" 

Cu.ft. 
R.P.M. 
B.H.P. 

8040 
280 
1.99 

11340 
394 
5.6i 

16010 
557 
16.39 

3 

18" 

Cu.ft. 
R.P.M. 
B.H.P. 

1410 
381 
0.167 

2820 
762 
1-33 

398o 
1076 
3-75 

90 

64" 

Cu.ft. 
R.P.M. 
B.H.P. 

12950 
218 
3.21 

18300 
308 
9.06 

25800 
435 
25-52 

4 

24" 

Cu.ft. 
R.P.M. 
B.H.P. 

2500 
286 

o.  296 

5000 

572 
2.35 

7080 
807 
6.64 

120 

85" 

Cu.ft. 
R.P.M. 
B.H.P. 

24200 
164 
6.00 

34300 
232 
17.05 

48300 
328 

47-85 

6 

36" 

Cu.ft. 
R.P.M. 
B.H.P. 

5650 
190 

0.665 

11300 
381 
5-30 

15900 
538 
15.0 

160 

113" 

Cu.ft. 
R.P.M. 
B.H.P, 

43250 

121 
10.67 

61100 
174 
30.00 

86200 
247 
85.25 

8 

48" 

Cu.ft. 
R.P.M. 
B.H.P. 

10000 

143 

1.18 

20000 
286 
9.40 

28300 
4«3 
26.6 

200 

141" 

Cu.ft. 
R.P.M. 
B.H.P. 

7000O 
99 
17.  16 

98900 
140 
48.95 

139500 
198 
138.00 

10 

60" 

Cu.ft. 
R.P.M. 
B.H.P. 

15650 
114 
1.84 

31300 
228 
14-7 

44200 
322 
41.6 

250 

176" 

Cu.ft. 
R.P.M. 
B.H.P. 

116050 
79 
28.93 

163960 

112 
80.96 

231410 
158 
231.41 

12 

72" 

Cu.ft. 
R.P.M. 
B.H.P. 

22600 
95 
2.66 

45200 
190 

21.2 

63600 
269 
59-8 

30O 

211" 

Cu.ft. 
R.P.M. 
B.H.P. 

174790 
66 

44.22 

246950 

94 
129.30 

348540 
132 
348.54 

IS 

90" 

Cu.ft. 
R.P.M. 
B.H.P. 

35250 
76 
4.14 

7O5OO 
152 

33.1 

99600 
214 
93-6 

350 

246" 

Cu.ft. 
R.P.M. 
B.H.P. 

245500 
57 
61.38 

340770 
80 
173.38 

489410 
H3 
489.41 

To  apply  the  tables,  use  data  from  the  school  building. 
The  friction  head  in  the  pipes  is  33  ft.  of  air,  which  is  J  in.  of 
water.  The  loss  in  the  two  Vento  heater  stacks  is  0.07  in. 
These  with  the  loss  in  the  fan  may  be  taken  as  f  in.  The 
quantity  to  be  handled  is  1,820,000  cu.ft.  per  hour. 

f  in.  =  0.75  of  peripheral  speed; 
i  .00  =  peripheral  head ; 


0.133^  = 


=  66.9V/i.oo  = 
1820000 


ft.  per  second; 


66.9X60X60' 


226          ELEMENTS   OF  HEATING  AND  VENTILATION 

i 


DIMENSIONS    OF    SIROCCO    FAN 


No.  of 
Fan. 

Diam. 
of 
Wheel. 

A 

B 

C 

D 

E 

F 

G 

H 

M 

I 

K 

0 

J 

N 

2* 

IS 

10 

9A 

14 

IS 

14 

13 

91 

13* 

10 

10 

i6| 

61 

10 

3* 

3 

18 

12 

1  1  A 

17 

18 

IS 

10* 

IS* 

12 

12 

19 

7* 

12 

4* 

3* 

21 

14 

I3lT 

20 

21 

18* 

I7l 

12 

18 

14 

13 

21* 

8* 

14 

4 

24 

16 

23 

24 

20* 

I9J 

13* 

19* 

16 

15 

3-g 

24* 

10 

16 

6 

4* 

27 

IS 

I7A 

26 

27 

23 

22 

IS 

21; 

18 

16 

29 

II 

18 

6* 

S 

30 

20 

i8H 

29 

30 

25* 

24; 

I6J   22j 

20 

17 

32 

12* 

20 

7* 

6 

36 

24 

22j| 

35 

36 

30* 

29' 

20i|  26j 

24 

21 

38 

IS 

24 

9 

7 

42 

28 

26A 

41 

42 

35 

33i 

23*   29i 

28 

23 

44 

17* 

28 

10* 

8 

48 

32 

3oA 

47 

48 

39* 

37i 

27 

32 

32 

127 

50 

20 

32 

10* 

9 
10 

8 

36 
40 

37H 

52 

58 

44 
48* 

421 
47; 

31* 
35 

35 
36 

36 

40 

28* 
32 

8 

22* 
25 

36 

40 

12 
12 

II 
12 

66 

72 

44 
48 

64 
70 

66 

72 

S3 

57* 

51; 
SSi 

38* 
42 

39 
43* 

3 

68 

74 

27* 

30 

44- 
48 

13* 
13* 

DIMENSIONS    OF    BUFFALO    FORGE    FAN 


Size  in 
Inches 


30 
35 
40 
45 
SO 
55 
60 
70 
80 
90 

IOO 

no 
120 
130 
140 
150 


Diam. 
Wheel. 

22 
25* 
29 
32* 
36 
39* 
43 
50 
57 
64 
71 
78 
85 
92 
99 
106 


"i 

13* 

IS 

161 

18* 

19! 

22! 

26 

29! 

33* 

37l 

41 

44 


6of 


E 


15*  14 

X 

i*B 

28AJ26 

31*  *8 


F&G 


||l 

18 

20 
22 

24  A 
28* 

32  A 

361 

40  A 

44* 


H 


M 
IS 

1 6 
10 
21; 
23 
25 

28 

30* 

33 

35f 

37* 


56   69i 


17* 
19 

201 
22j 
24 

301 

If 

43* 
471 

lit 


19  A 


INDIRECT  HEATING  227 

This  is  large; 

^  =  36"; 


7-54* 
The  power  to  drive  the  fan  is  given  by 

1 8  20000  X  14.7X144 
Power= 

-—2  -,  0.405 


=2.5  H.P.  with  an  efficiency  of  35  per  cent.    This  would 
require  7.1  H.P. 

It  is  better,  however,  to  use  tables  of  the  makers  for  sizes  and 
dimensions. 

From  the  table,  since  i  in.  is  approximately  ^  oz.,  a  gg-in. 
wheel  at  141  rev.  will  be  required  to  deliver  32,800  cu.ft.  of  air 
per  minute.  This  requires  8.14  H.P.  To  deliver  just  30,000 
cu.ft.  this  fan  will  be  run  at 


The  power  consumed  will  be 


The  pressure  will  be 


If  this  pressure  is  not  sufficient  the  fan  will  have  to  be  run 
faster  and  the  quantity  will  be  changed  from  the  point  of  max- 
imum efficiency,  as  there  will  not  be  the  same  relation  between 


228 


ELEMENTS   OF  HEATING  AND  VENTILATION 


velocity  head  and  friction  head  as  that  at  a  proper  speed  and 
pressure. 

For    a   Sirocco  fan  a  6o-in.  fan   at  134   R.P.M.  would  be 

required,  and  this  would  use  7.48 
H.P.  This  would  be  treated  in 
the  same  manner  as  above  to  get 
exact  conditions. 

The  dimensions  of  the  hous- 
ings of  these  fans  would  be  found 
from  the  tables. 

The  further  application  of 
this  method  of  heating  will  be 
applied  to  a  shop  building  shown 
in  Fig.  162. 

In  this  building  there  are 
11,200  sq.ft.  of  wall  space  of 
i6-in.  concrete,  13,600  sq.ft.  of 
glass,  20,000  sq.ft.  of  concrete 
roof  and  750,000  cu.ft.  of  air. 
There  are  300  men  employed  in 
the  building. 

The  amount  of  air  required 
for  ventilating  would  be 

3OO  X  2000  =  600000 

cu.ft.  per  hour. 


FIG.  162. — Shop  Building. 


This  is  much  less  than  the 
volume  of  the  room,  and  with  as 
much  window  space  as  is  here  used  the  leakage  from  the  windows 
will  keep  the  air  sufficiently  fresh  so  that  a  heating  system 
will  be  used  in  which  the  air  is  recirculated  from  the  shop. 
The  heat  required  is  found  as  follows: 

Temperature  shop,  55°  F.; 
K  for  glass,  0.96; 
K  for  concrete,  0.26; 
K  for  roof,  0.30. 


INDIRECT  HEATING  229 

H  =  (55  —  o)[o.26  X 1 1200+0.3  X  20000+0.96  X 13600] ; 
=  55X21968  =  1208240  B.t.u. 

If  the  air  is  to  be  heated  to  85°  F.,  the  amount  of  air  to  be 
circulated  will  be: 

1208240 

=2014000  cu.ft.  per  hour, 

0.02X30 

or  about  three  changes  of  the  volume  of  the  room. 

In  some  cases  this  air  might  be  carried  through  a  filter  before 
entering  the  fan  again,  thus  cleaning  the  atmosphere,  and  in  case 
of  mill  heating  the  proper  humidity  might  be  obtained  in  this 
way. 

Since  2,000,000  cu.ft.  per  hour  is  a  large  quantity,  it  might 
be  advisable  to  separate  the  system  into  two  parts.  Moreover 
the  crane  run-way  must  be  left  clear,  and  the  only  way  of 
distributing  to  both  sides  if  one  fan  were  used  would  be  to  cross 
over  at  the  end  of  the  building  or  use  an  underground  duct. 
For  simplicity  and  economy  it  is  well  to  place  heaters  near 
the  center  of  the  building. 

In  this  system  quietness  is  not  so  important  as  smallness  of 
pipes,  and  for  that  reason  high  velocities  of  2500  ft.  per  minute 
will  be  used  in  the  pipes,  while  500  ft.  will  be  used  at  ends  of 
branches.  There  will  be  an  opening  in  each  bay,  as  shown  on 
Fig.  162,  for  space  beneath  gallery  and  roof.  The  velocity 
through  the  heater  will  be  2000  ft.  per  minute. 

The  temperature  of  the  air  leaving  is  85°  F.,  which  with 
zero  air  and  5  Ibs.  steam  will  require  four  sections  of  Vento 
heaters.  The  entering  air  is  at  55°,  which  requires  two  sections. 
Hence  the  difference,  or  two  sections,  must  be  used  to  heat  the 
air  from  55°  to  85°. 

At  2000  ft.  the  heat  transmission  for  the  two  sections  is 

2380X4  —  2670X2 
-^—  -  or  2090  B.t.u. 

2 

The  heating  surface  required  will  be 

1208240 

-  =  578  sq.ft. 

20QO 


230          ELEMENTS   OF  HEATING  AND  VENTILATION 

The  amount  per  heater  will  be  289  sq.ft.  and  the  amount  per 
stack  will  be  145  sq.ft.  The  area  required  through  heater  will 
be 

IO07OOO 

=  8.4  sq.ft. 


2000  X  60 

ii  5o-in.  sections  with  5-in.  centers  will  give  this. 

To  cut  down  the  area  required  a  higher  temperature  will  be 
used.  Suppose  five  sections  be  used  in  the  heater;  this  means 
then  that  the  condition  is  that  of  a  5-heater  system  where  the 
air  has  passed  through  two  sections.  The  temperature  of  the 
air  leaving  is  then  120°  F.  and  the  heat  transmission  is 


3 
The  heating  surface  is  then 

1208240 
1803 


=  670  sq.ft. 


or  335  sq.ft.  on  each  side  of  the  building.  This  means  112 
sq.ft.  to  each  stack.  The  air  now  used  will  be 

1208240 
-  —7  -  7  =  030000  cu.ft. 

0.02X(l20-55) 

or  a  little  over  one  change  per  hour.  The  amount  for  each  heater 
is  7750  cu.ft.  per  minute.  The  area  through  the  heater  should 
then  be 


A  Q-sec.  50  in.  high  4!  in.  centers  would  have  the  correct  heating 
area,  but  the  area  for  the  air  passage  is  5.85  sq.ft.  A  lower 
velocity  must  then  be  taken.  Suppose  700  ft.  be  assumed. 


INDIRECT  HEATING  231 

Then  i  sec.  will  give  40°  F.  and  4  sec.  118°  F.     The  heat  per 
sq.ft.  for  the  three  sections  will  be 

1200X4— 1600 

=  1100 

3 

1208240 


This  will  not  give  the  desired  result.     The  first  result  is  the 
best  combination. 

2010000 
Air  by  each  fan  = =  1000000, 

or  16700  cu.ft  per  minute. 

Air  to  each  floor  8350  cu.ft.  per  min.; 
Air  to  each  branch  4175  cu.ft.  per  min.; 
Air  to  each  outlet  1040  cu.ft.  per  min. 


1040 

Area  of  outlet  —   —  =  2  sq.ft. 
500 


1040 
Area  of  last  section  — —  X 144  =  59  sq.in. 


Area  of  2d  section  from  end 

2080 

-  =  —  -x  144  =  118  sq.in. 
2500 


Area  of  3d  section  =  177  sq.in.      #  =  15. 

Area  of  4th  section  =  236  sq.in.     D  =  1 7  \  in. 

Area  of  vertical  riser,  462  sq.in.     D  =  24. 

Area  of  vertical  riser  from  fan  =  Q24  sq.in.  =31X31 


232          ELEMENTS  OF  HEATING  AND  VENTILATION 
Drop  in  pressure  due  to  friction. 

0.02  X  2  S        A22 

ist  section,    h  = a  X?-  =  18  ft.  of  air 

•75          64 

=  0.26  in.  of  water. 


2d  section,     h  =  o.26  in.  X— —  =  0.19  in.  of  water. 


3d  section,     7/  =  o.26  in.  X —  =  0.15  in.  of  water. 


4th  section,    h  =  o.26  in.  X =0.13  in.  of  water. 


o       12 

Riser  ist  to  2d,  0.26 X X  —  =  0.05. 

17-5     25 

O         IO 

Main  riser,  o.26X — X —  =  0.03. 

o 

Loss  in  bends  =  0.1 5  —  -  =9  ft.  air  or  0.13  in.  water. 
04 

Total  loss  in  pressure: 

Last  branch  and  nozzle o .  05  (assumed) 

Bend 0.13 

Last  section 0.26 

2d  section 0.19 

3d  section 0.15 

4th  section 0.13 

Bend o.  13 

2d  floor  riser 0-05 

ist  floor  riser •  0.03 

Bend 0.13 

Fan 0.20 

2  section  heater 0.45 


Total i .  90' 


INDIRECT  HEATING 


233 


This  is  the  total  resisting  pressure.     The  dynamic  pressure  is 

I  GO 

—  =  2.6  ins.    Use  2  oz.     Then  from  the  tables  two   No.  70 
•75 

steel-plate  fans  with  wheels  50  ins.  in  diameter  will  be  required 
when  run  at  557  R.P.M.  and  each  using  16.39  H.P.  These 
each  give  16,011  cu.ft.  The  Sirocco  table  gives  2  No.  6  fans 
with  diameters  36  ins.  at 
538  R.P.M.  and  using  15.0 
H.P.  These  each  give 
15,900  cu.ft.  They  may 
be  speeded  down  to  give 
the  exact  discharge,  as 
was  done  with  the  school- 
house  fan.  If  larger  pipes 
could  be  used  and  the  area 
through  the  heaters  made 
greater  to  cut  the  velocity 
to  one-half  its  value,  the 
resistance  should  be  J  of 
this  or  |  oz.  This  would 
require  two  No.  100  fans 
of  71  ins.  diameter  at  197 
R.P.M.  and  would  use  4.11 
H.P.  giving  16,610  cu.ft. 

The  Sirocco  fan  for 
this  service  would  be  a 
No.  9-54  ins.  diam.  fan  at 
179  R.P.M.  using  4.20  H.P. 
and  giving  17,950  cu.ft. 

In  all  cases  it  is  advisable  to  use  as  low  a  velocity  as  possible, 
but  in  some  cases  the  size  of  pipe  is  the  important  matter. 

In  cases  where  steam  engines  are  employed  and  the  exhaust 
steam  is  used  in  coils,  the  excessive  power  loss  is  not  important, 
as  it  is  changed  into  heat  and  used  in  the  building.  This  same 
is  true  in  a  plant  using  electric  power  when  it  is  made  on 
the  premises  and  the  exhaust  steam  is  used  for  heating. 
It  is  simply  a  matter  of  cost  of  production  of  power,  as  electrical 


FIG.  163. — Small  Factory. 


234 


ELEMENTS  OF  HEATING  AND  VENTILATION 


power  or  thermal  power.     If  i  B.t.u.  of  heat  can  be  produced 

as  heat  in  the  coils  at ct.   while    i   B.t.u.   of   electrical 

50000 


energy  costs 


ct.,  it  is  evident  that  the   power  consumed 


& 


O 


151 


FIG.  164. — Mill  Heating,  Using  Buttress. 

by  the  fan  should  be  reduced  to  as  small  a  quantity  as  possible 
if  an  electric  motor  is  to  drive  it. 

The  following  figures  are  prepared  from  cuts  showing  the 
work  of  the  B.  F.  Sturtevant  Co. 

Fig.  163  illustrates  a  method  of  introducing  air  into  a  small 
factory,  while  Fig.  164  shows  how  underground  ducts  and  but- 
tresses may  be  used  in  mill  buildings.  The  use  of  brick  ducts 


INDIRECT  HEATING 


235 


IF?    LJ 
I 


FIG.  165. — Damper  for  Wall  Duct. 


FIG.  1 66.— Indirect  Heating  of  Theater. 


236          ELEMENTS  OF  HEATING  AND  VENTILATION 

underground  is  important  in  many  cases.  The  problem  is  the 
same  as  with  metal,  the  constant  /  being  increased  as  mentioned 
earlier.  In  Fig.  165  the  form  of  damper  used  in  such  a  plant  is 
given;  such  dampers  must  be  operated  from  the  floor  of  the  room. 
This  arrangement  is  not  as  advantageous  as  one  in  which  the 
air  is  carried  M  the  interior  of  the  building,  as  there  is  loss  of  heat 
through  the  walls!  of  the  flues.  Similar  buttresses  may  be  used 
to  remove  the  foul  air,  although  unless  the  product  of  manufac- 
ture vitiates  the  air  there  are  so  few  occupants  that  this  air 
may  be  recirculated,  using  screens  or  niters  to  remove  dirt. 

Fig.   1 66  illustrates  the  method  of    applying  this  system 
to  a  theater. 


CHAPTER  IX 
FURNACE  HEATING 

As  described  in  Chapter  I,  furnace  heating  is  a  system  in 
which  hot  air  is  introduced  from  a  furnace  into  the  rooms  to  be 
heated.  The  air  may  be  introduced  to  the  heating  tubes  of  the 
furnace  from  the  outside  or  it  may  come  from  the  interior  of  the 
building  through  the  recirculating  duct.  This  latter  method  may 
be  used  in  residences  or  in  buildings  where  there  are  not  so  many 
occupants,  the  leakage  from  the  windows  and  doors  giving 
sufficient  fresh  air.  The  former  method  must  be  employed  in 
schools,  churches  or  audience  rooms  heated  by  furnaces,  on 
account  of  the  large  amount  of  fresh  air  for  ventilation. 

The  first  consideration  in  this  method  of  heating,  as  in  all 
methods,  is  the  necessary  heat  to  care  for  the  losses,  then  the 
amount  for  the  ventilating  air,  and  finally  one  must  consider 
the  temperature  at  which  the  air  must  enter  in  order  to  supply 
the  heat  loss  before  being  reduced  to  the  room  temperature. 

The  method  of  Chapter  V  is  used  to  find  the  heat  losses 
and  then  the  assumed  amount  of  air  for  ventilation  is  used  to 
find  the  temperature  at  which  this  air  must  enter. 

TT 


where  /«  =  temperature  of  entering  air  in  deg.  F.; 
tr  =  temperature  of  room  air  in  deg.  F.  ; 
17  =  heat  loss  per  hour  in  B.t.u.; 
F  =  volume  of  air  per  hour  in  cubic  feet. 

The  air  assumed  as  the  ventilating  air  or  leakage  air  may 
give  so  high  a  value  of  ti  that  the  amount  of  air  must  be  increased. 
This  does  not  necessarily  mean  that  the  air  from  the  outside 

237 


238 


ELEMENTS   OF  HEATING  AND  VENTILATION 


must  be  increased,  but  that  passing  through  the  heating  tube. 
A  large  part  of  this  may  come  from  the  recirculated  air  in  resi- 
dences. 

The  house  of  Chapter  V  will  now  be  examined.  As  men- 
tioned in  Chapter  VIII  an  examination  of  the  air  supply  to  the 
various  rooms  will  show  that  the  leakage  air  assumed  is  too 
small,  as  the  temperatures  are  all  high.  If  130°  F.  is  assumed 
as  a  good  temperature  for  this  air  the  quantity  in  cubic  feet  at 
70°  will  be  that  found  in  the  table  below  which  is  prepared  in 
addition  to  those  of  Chapter  V  for  the  furnace  system  of  heating 
this  house. 


Total  Heat 

for  Various  i 

Vmounts  of 

Heat  Loss, 

Ventilation, 

Outside  Air. 

Room. 

B.t.u.  per 
Hour. 

Cubic  Feet 
per  Hour. 

Full  Outside 

One-half 

No  Outside 

Air. 

Outside  Air. 

Air. 

I 

16810 

14000 

130 

36500 

26600 

16800 

2 

11792 

9600 

130 

25000 

18200 

IlSoo 

3 

1745 

1450 

130 

3800 

2800 

1700 

4 

6890 

5700 

130 

14800 

10800 

7OOO 

5 

8740 

7300 

130 

19000 

13900 

8700 

6 

10635 

8900 

130 

23200 

17000 

10600 

7 

14050 

11700 

130 

30400 

22300 

14000 

8 

8750 

7300 

130 

19000 

13900 

8700 

9 

2170 

1800 

130 

4700 

3300 

2200 

10 

7680 

6400 

130 

16600 

I22OO 

7700 

ii 

8330 

7000 

130 

18200 

13400 

8300 

12 

2840 

2400 

130 

6200 

4600 

2800 

100432 

83^0 

217400 

I  ^OOOO 

IOO"?OO 

ooo 

j.  ^ywww 

±\J^>J^\J\J 

The  column  marked  total  heat  with  full  outside  air  has  been 
computed  by  the  formula: 

H  =  0.02V  (tt-  10)     .     .     ."    .     .   '.     (151) 
while  the  column  for  one-half  outside  air  has  been  found  by 

-/J       .     .     .     .     (152) 


(i53) 


0.02V  \Ti-  —  - 


FURNACE  HEATING  239 

Since 

Heat  loss  =  0.02 F[r«- TV] (154) 

V  in  all  of  the  cases  is  the  volume  at  70°.  The  computa- 
tions are  made  with  a  slide-rule  in  all  work  of  this  nature,  as 
the  original  data  and  the  variation  in  conditions  do  not  warrant 
a  greater  degree  of  accuracy. 

The  table  shows  well  the  cost  of  ventilation.  With  no  fresh 
air  ioo;ooo  B.t.u.  are  required  per  hour.  With  50  per  cent 
efficiency  of  furnace  and  with  coal  of  14,000  B.t.u.  this  means 
14  Ibs.  of  coal  per  hour.  With  the  air  taken  entirely  from  the 
outside,  the  heat  required  amounts  to  217,000  B.t.u.  and  re- 
quires about  31  Ibs.  of  coal  per  hour.  The  leakage  mentioned 
in  the  table  of  Chapter  V  of  30,000  cu.ft.  from  the  outside  is 
about  three-eighths  of  the  amount  necessary  to  keep  the  enter- 
ing temperature  at  130°  F.  and  if  this  came  in  it  would  mean 
the  supply  of  144,000  B.t.u.  per  hour,  or  21  Ibs.  of  coal.  The 
full  amount  of  air  would  care  for  about  45  persons,  while  the  leak- 
age of  Chapter  V  would  care  for  18  persons,  a  number  which 
would  be  too  large  even  for  this  house  for  continuous  use.  Hence 
the  value,  and  necessity  even,  for  inside  circulation  in  residences 
is  quite  evident.  In  most  cases  the  leakage,  in  on  the  windward 
side  and  out  on  the  leeward  side,  is  sufficient  to  care  for  the 
ventilation  of  the  rooms,  and  this  amount  of  leakage  is  likely 
to  occur  though  all  of  the  air  for  the  furnace  is  taken  through 
the  inside  recirculation  duct. 

Having  found  the  amount  of  heat,  the  next 
on  the  location  and  size  of  the  various  pipes,  flues 

The  location  of  registers  is  important.  If  located  in  the  wall  * 
they  may  interfere  with  the  placing  of  furniture  and  are  limited 
in  size  according  to  the  size  of  the  partition,  while  if  placed  in 
the  floor,  although  better  as  far  as  size  and  directness  are  con- 
cerned, they  mean  a  cutting  of  carpets  or  floors,  to  which  some 
householders  object,  and  they  collect  dust  and  dirt.  When 
placed  in  the  floor,  however,  they  offer  a  more  direct  path  and 
for  that  reason  it  is  very  advisable  to  place  them  in  this  manner 
on  the  first  floor,  where  there  is  little  head  causing  flow. 


step  is  to  decide  J    / 
ss  and  registers. 


240          ELEMENTS  OF  HEATING  AND  VENTILATION 

The  head  causing  flow  is  the  difference  in  weight  between 
the  column  of  hot  air  and  cold  air,  and  as  mentioned  in  Chapter 
VIII,  this  head,  expressed  in  feet  of  hot  air,  is, 


i_    _pi\ 
T2    RTj 


LRT2 

~L  '     *    '    '     (  55) 


TI  —  absolute  temperature  of  inlet  air; 
7^2  =  absolute  temperature  of  air  at  bottom  of  heater; 
=  TT  approximately. 

If  this  is  applied  as  before  to  the  various  heights  from 
registers  to  base  of  heater,  say  10,  20  and  30  ft.,  the  following 
heads  result,  for 

^1  =  130;  ^1=590; 

fe  =  60°  F.  (due  to  mixture  of  some  cold  air)  : 


#2  =  2.70; 
Hz  =  4-05- 

The  pipes  leading  to  the  vertical  flues  or  stacks  are  known 
as  leaders.  In  these,  the  velocities  will  vary  with  the  sizes  of 

the  pipe  (fixing  the  hydraulic  radii,  -p  j,  with  the  length  of  the 

run,  the  number  of  bends,  etc.     The  following  problems  will 
give  an  idea  of  the  results  to  be  expected.     (See  p.  198.) 

i  st.  Find  the  velocity  in  the  pipe  to  a  first-floor  register  with 
a  i5-ft.  run  of  i2-in.  pipe  and  a  bend  of  radius  equal  to  the 
diameter. 


2d.  Find  the  velocity  to  be  expected  in  a  14X3!  flue  run- 


FURNACE  HEATING  241 

ning  to  second  floor  with  two  sharp  right-angle  turns  and  10 
ft.  of  lo-in.  pipe. 


V  12  4  12X35 

In  this  way  the  velocity  may  be  found  for  any  given  condi- 
tion, but  in  general  the  velocity  for  the  various  floors  will  be 
assumed.  The  values  given  below  are  those  which  may  be 
expected  in  practice: 

ist  floor,  4.0  to  5  ft.  per  sec.; 
2d  floor,  5.0  to  6.5  ft.  per  sec.; 
3d  floor,  6.0  to  7.5  ft.  per  sec. 

Having  the  velocities  to  the  different  floors,  the  areas  of  pipes 
and  flues  are  found. 

VXc 

-  .......     (156) 


Thus  where  c  =  the  factor  to  care  for  temperature  as  found  in 
the  table  of  p.  209,  for  room^2  of  the  house  considered  in  Chapter 
V,  the  area  will  be 

9600X1.11X144 

Area  =  -  -  ——,  -  =  106  sq.in. 
4X3600 

This  requires  a  pipe  nf  ins.  in  diameter.  A  i2-in.  pipe 
will  be  used. 

The  area  of  the  registers  will  be  fixed  by  the  allowable  velocity 
of  discharge.  This  may  be  taken  as  4  ft.  per  second  on  all 
floors,  giving 


cV  f      . 

Net  area  reg.  =  -  =  -  in  sq.in.     .     .    .     (157) 
14400     100 


242 


ELEMENTS  OF  HEATING  AND  VENTILATION 


Since  the  net  area  is  66  per  cent  of  the  gross  area  of  opening  into 
which  the  register  fits  the  area  of  the  opening  is  given  by 


(158) 


Area  opening  =  —77-  -  =  o.oi  5  Vc. 

0.66X14400 

In  the  case  above  this  equals 

0.015X9600X1.11  =  160  sq.in. 


A  io//Xi6//  register  would  be  required. 

If  vent  stacks  are  used  Hoffman  recommends   that   their 
areas  be  made  0.8  of  the  heat  stack  areas. 

The  pipes  leading  to  the  stacks  are  in  some  cases  made  larger 


FIG.  167. — Furnace  with  Flat 
Bonnet. 


FIG.  168. — Furnace  with  Conical 
Bonnet. 


in  area  than  the  stacks  supplied  by  them  to  cut  down  resistance. 
This  must  be  done  in  cases  of  long  runs,  although  in  short 
runs  it  is  not  necessary. 

Before  applying  these  formulae,  however,  it  is  well  to  plan 
the  location  of  the  heater  and  the  location  of  the  various  flues 
or  stacks. 

Stacks  should  be  run  in  the  inside  partitions,  as  there  would 
be  considerable  heat  loss  if  placed  in  outside  walls.  Circulation 
is  better  cared  for  if  applied  here,  as  the  hot  air  rising  naturally 
starts  the  cold  air  across  the  floor  from  the  other  side  and  thus 
gets  the  air  in  motion.  If  placed  in  an  outer  wall  the  cold  air 
from  the  wall  may  start  a  down  current  of  air  in  the  stack, 
thus  choking  off  the  supply.  The  furnace  method  of  heating 
is  different  from  steam  heating,  in  which  radiators  form  strong 


FURNACE  HEATING 


243 


up  currents   due   to   the   higher   temperature.     The   principal 
objection   to   furnace   heating    is    the    absence    of    a  positive  I  j 
circulating  force. 

The  leaders  or  pipes  leading  across  the  cellar  from  the  heater 
are  taken  from  the  top  of  the  casing  around  the  heater.  This 
.casing  may  have  a  flat  top  as  shown  in  Fig.  167  or  it  may  have 
a  cone  top  or  bonnet  as  shown  in  Fig.  168.  Although  the  flat 
top  receives  the  hot  air  more  directly  from  the  furnace  it  means 
that  there  will  be  more  head  room  needed  and  a  full  right-angle 
turn  will  have  to  be  used.  The  distance  above  the  castings 
to  a  flat  top  should  be  at  least  8  or  9  ins.  and  this  could  be  used 
to  advantage  on  a  slanting  side  cutting  down  the  bend  to  45 
>or  60°  instead  of  a  right  angle.  The  slant  height  of  the  bonnet 


FIG.  169. — Register  Floor  Box. 

should  be  about  3  ins.  greater  than  the  largest  pipe  to  be  taken 
from  it.  To  aid  in  sending  the  air  to  the  edge  with  a  cone  top, 
an  inside  conical  center  is  used  as  dotted  in  Fig.  168.  This 
sends  the  air  to  the  outside.  Sometimes  a  long  leader  is  taken 
from  the  center  of  the  top  so  that  it  may  get  a  better  supply 
to  overcome  the  friction  of  the  great  length  or  the  long  pipes 
may  be  taken  from  the  rear  side  of  the  top,  but  never 
directly  over  the  point  where  the  cold  air  enters  nor  near  the 
edge  of  a  flat  top  where  it  might  start  currents  along  the  cold 
casing.  To  aid  the  circulation  in  long  pipes  or  to  pipes  on  the 
exposed  sides  of  a  building  the  leader  is  sometimes  continued 
inside  of  the  bonnet  with  an  enlarged  hood,  so  that  the  hot  air 
may  be  directed  into  it,  and  in  some  cases  positive  circulation 
is  attained  by  connecting  certain  leaders  to  a  number  of  the  heat- 


244 


ELEMENTS  OF  HEATING  AND  VENTILATION 


ing  tubes  of  the  furnace.  The  furnace  should  be  so  placed  that 
the  runs  for  the  leaders  on  the  exposed  sides,  usually  the  north 
and  west,  are  shorter  than  the  others,  but  the  heater  should  be 
placed  so  as  to  make  all  as  short  as  possible. 

The  leaders  are  carried  to  the  register  boxes,  Fig.  169,  for 
the  floor  registers  of  the  first  story,  or  the  shoes  or  boots,  Fig. 
170,  at  the  bottom  of  the  heat  flues  or  heat  stacks  which  run 
to  higher  floors.  The  boxes  for  the  floor  registers  should  be 


FIG.  170. — Shoes. 


FIG.  171. — Damper. 


made  with  no  projecting  fins  to  obstruct  the  flow  of  air  and  the 
4-in.  collar  at  the  bottom  should  be  connected  with  the  leader 
by  an  elbow  at  least  equal  to  the  diameter  of  the  leader.  The 
register  box  is  about  4^  to  6  ins.  deep  to  allow  the  air  to  reach  the 
ends  of  the  register  face  with  little  obstruction.  The  elbow 
should  fit  the  pitch  of  the  pipe.  The  pitch  should  be  not 
less  than  i  in.  per  foot.  This  pitch  is  advisable  for  starting 
the  circulation,  although  for  a  pipe  running  full  of  a  fluid  with 
a  definite  difference  in  head  between  the  ends  the  velocity  of 


FURNACE  HEATING  245 

the  fluid  is  theoretically  independent  of  the  pitch.  In  furnace 
work,  however,  the  difference  of  head  is  small  and  the  substance 
has  such  a  small  density  that  there  may  be  currents  in  two  direc- 
tions in  the  same  pipe  and  for  these  reasons,  although  the  formulae 
for  fluids  have  to  be  used,  there  is  the  need  of  considering  the 
peculiarities  of  the  substance.  Thus  pipes  are  pitched  as  much 
as  possible  and  circulation  is  aided  thereby. 

The  leaders  are  connected  to  co  lars  about  5  ins.  long,  which 
are  attached  to  the  bonnet  of  the  furnace.  The  tops  of  the  col- 
lars should  all  be  on  the  same  level  so  that  they  will  all  offer 
the  same  resistance  to  flow.  All  leaders  except  one  should  be 
provided  with  tight-fitting  dampers,  Fig.  171,  so  that  the  heat 
may  be  cut  off  when  necessary.  Some  one  leader  should- 
be  arranged  so  that  it  cannot  be  cut  off  in  order  that  there 
may  be  no  danger  of  closing  all  outlets  and  heating  the 
air  within  the  casing  so  much  that  fires  may  occur. 

If  there  is  only  one  outlet,  as  is  the  case  at  times  in  church 
heating,  this  connection  should  be  without  a  valve  or  damper 
of  any  kind. 

The  leaders  for  the  second  floors  or  for  registers  placed  in 
the  walls  are  attached  to  boots  or  shoes,  Fig.  170,  which  form 
the  lower  parts  of  the  flues  or  stacks. 

The  shoe  A  or  B  is  intended  to  be  used  when  the  leader  is 
at  right  angles  to  the  partition,  while  C  and  D  are  used  when 
the  leader  runs  parallel  to  the  partition.  E  and  F  are  employed 
when  elbows  are  used  to  join  the  leader  and  shoe.  Shoe  B 
requires  no  bend  at  the  end  of  the  leader  to  accommodate  the 
pitch  and  therefore  should  offer  small  resistance.  The  slanting 
back  of  A  is  of  little  value. 

The  shoe  shown  at  C  is  used  when  it  is  necessary  to  offset 
for  the  leader.  The  stacks  are  made  of  single  or  double  thick- 
nesses of  tin.  The  ordinary  partitions  are  made  of  3  X4  or  2  X4- 
in.  studs  placed  16  ins.  apart.  These  will  allow  one  to  use 
13X4-  or  i4X4-in.  stacks  as  the  largest  single  stacks  and  in 
that  way  the  amount  of  heat  taken  for  a  single  register  face  is 
limited.  Stacks  are  usually  made  rectangular  in  form  on  account 
of  space  limitation,  but  the  nearer  the  form  approaches  a  circle 


246 


ELEMENTS  OF  HEATING  AND  VENTILATION 


or  square,  the  better  it  is  for  carrying  a  fluid.  The  fric- 
tion of  a  conduit  depends  on  the  reciprocal  of  the  hydraulic 
radius  which  is  the  ratio  of  the  area  of  the  section  to  the  perim- 
eter of  the  sections  and  this  is  larger  for  the  circle  and  square 
(\d)  than  for  any  other  form  of  area.  Stacks  are  some- 
times made  with  double  walls,  to  cut  down  radiation  and 

to  prevent  charring  the  wood 
if  hot.  Some  advise  having  single- 
thickness  stacks  covered  with  as- 
bestos paper.  These  stacks  end  in 
register  boxes,  Fig.  172.  A  repre- 
sents the  ordinary  form  where  the 
box  is  placed  at  the  end  of  the  riser 
or  stack  and  B  showrs  one  which 
does  not  require  the  full  width  of 
the  stack.  The  figure  also  illus- 
trates a  box  which  takes  part  of 
the  supply  of  a  stack,  the  remain- 
ing part  going  to  the  room  above. 
This  method  is  used  at  times,  but 
it  is  not  the  best  way  to  supply 
heat  owing  to  interference.  For 
privacy  it  is  not  well  to  put  two  wall  registers  opposite  each 
other  on  the  same  stack. 

The  box  D  is  one  in  which  a  circular  top  register  is  to  be 
used  while  C  illustrates  a  method  for  first-floor  registers  in  order 
to  increase  the  area  of  flue.  To  increase  the  area  of  the  flue  for 
first-floor  wall  registers,  the  plaster  and  base  board  are  omitted 
at  these  points,  and  in  this  way  an  extra  inch  may  be  obtained. 
By  using  the  box  shown  at  C,  however,  in  which  the  special 
register  casting  fits  over  the  sides  of  the  box  as  shown  in  Fig. 
173,  a  much  greater  area  necessary  for  large  first-floor  rooms 
is  obtained.  The  registers  are  held  in  place  by  the  clips  shown 
on  the  boxes.  The  stacks  are  sometimes  turned  to  enter  floor 
boxes  on  an  upper  floor  and  it  is  then  necessary  to  use  an  elbow, 
A  or  B,  Fig.  174.  When  the  partition  through  which  the  stack 
passes  is  directly  over  the  cellar  partition  an  offset,  C,  Fig.  174,. 


C  D 

FIG.  172. — Register  Boxes. 


FURNACE  HEATING 


247 


is  used  on  which  to  attach  the  boot.     Fig.  175  shows  the  appli- 
cation of  these  various  fittings. 

The  tin  used  for  pipes  and  stacks  is  made  of  soft  sheet  steel 


nnonnnnn 
ccnnnnnnn 
raconnonn 
Uonnnnnno 
nononnnn 


FIG.  173. — Special  First  Floor 
Wall  Register. 


n 


FIG.  174. — Elbows  and 
Offsets. 


FIG.  175. — Stacks,  Shoes,  and  Leaders. 

coated  with  tin.  Originally  it  was  made  of  wrought  iron. 
Tin  is  gauged  by  numbers  or  letters.  The  trade  terms  from 
56  Ibs.  to  100  Ibs.  mean  the  weight  of  a  box  of  100  i4/'X2o" 


248          ELEMENTS  OF  HEATING  AND  VENTILATION 

sheets,  while  between  weights  of  107  Ibs.  and  215  Ibs.  to  the  box 
of  100  i4"X2o"  sheets,  the  tin  is  known  as  I  tin;  1C  being  107 
Ibs.  to  the  box,  IXL,  128  Ibs;  IX,  135  Ibs.;  IXX,  155  Ibs.  up 
to  IXXXXX,  215  Ibs. 

1C,  IX  or  IXX  tin  is  used  for  pipe  work,  the  latter  for  pipes 
over  12  ins.  in  diameter.  The  piping  and  stacks  are  often 
wrapped  in  asbestos  paper  to  make  all  the  joints  tight,  although 
this  does  not  cut  down  the  heat  loss  very  materially.  In  fact 
the  use  of  non-conducting  material  or  air  space  with  double- 
thickness  stacks  is  not  necessary  for  stacks  on  interior  walls, 
as  any  heat  escaping  is  used  to  warm  the  house.  To  cut  down 
loss  in  the  cellar,  some  type  of  air-cell  covering  or  thick  pipe 
covering  might  be  of  value  to  keep  the  cellar  cool.  This  heat 
escaping  in  the  cellar  is  not  wasted,  however,  unless  the  cellar 
is  heated  too  much  for  the  proper  storage  of  vegetables  and  fruits. 
The  heat  from  these  pipes  warms  the  cellar  and  thus  cuts  down 
the  loss  through  the  floor  from  the  first-floor  rooms. 

In  running  the  leaders  from  the  heater,  endeavor  should  be 
made  to  reduce  the  resistance  to  a  minimum  even  though 
special  cutting  must  be  made  on  the  fittings  of  the  piping  to  suit 
the  angles.  Thus  the  dotted  position  for  the  leader  of  Fig.  167, 
although  cheaper  to  make  because  of  the  use  of  standard  elbows, 
is  not  the  one  to  give  the  better  flow  of  heat  which  ^should  be 
the  aim  in  all  designs. 

For  school  heating  it  is  advisable  to  bring  the  air  in  from 
a  wall  register  placed  six  or  eight  feet  from  the  floor  and  to  have 
a  vent  register  near  the  same  point  at  the  floor  level.  In  some 
cases  this  is  not  possible  and  floor  registers  have  to  be  used. 
The  ventilating  stack  is  sometimes  made  effective  in  such 
installations  demanding  ventilation,  by  having  a  furnace  or 
hot  pipe  at  the  base  of  a  stack  which  heats  the  stack  air  and 
causes  it  to  rise.  This  produces  a  draft  which  sucks  impure 
air  from  the  proper  part  of  the  rooms  of  the  lower  story  while 
the  hot  air  is  made  to  pass  over  restricted  areas  at  the  upper 
floors,  causing  an  injector  action  and  sucking  the  air  from  the 
room.  If  the  furnace  gases  could  be  carried  up  through  a  central 
iron  flue  in  a  brick  ventilating  stack,  the  heat  from  the  flue 


FURNACE  HEATING 


249 


would  cause  the  air  around  it  in  the  stack  to  rise,  drawing  in 
air  from  the  various  rooms  on  the  stack  to  replace  it. 

At  times  it  is  necessary  even  with  hot-air  furnaces  to  use 
fans  to  produce  the  necessary  circulation,  Fig.  176.  This  occurs 
in  large  work  only  when  some  of  the  rooms  to  be  heated  are  at 
considerable  distance  from  the  heater.  In  school  work  or  other 
large  buildings,  several  heaters  may  be  placed  at  convenient 
locations,  each  heater  caring  for  a  set  of  adjacent  rooms.  This 
method  requires  several  chimneys,  but  these  are  easily  built 
when  the  necessary  ventilation  flues  are  formed. 


FIG.  176. — Fan  Circulation  with  Twin  Hot-air  Furnaces. 

The  principles  are  now  applied  to  the  house  considered 
earlier  and  the  layout  of  heater  and  piping  of  Fig.  177  is  made 
for  the  cellar,  in  conjunction  with  the  plans  of  the  rooms,  Fig. 
178.  The  heater  is  placed  near  the  north  and  west  side  but 
the  pipes  are  mainly  on  three  sides  of  the  heater.  Hence  the 
room  behind  the  heater  or  the  central  passage  of  the  cellar  would 
have  been  far  better  had  the  use  of  the  cellar  rooms  and  the  loca- 
tion of  the  chimney  permitted  it.  In  many  cases  the  location 
of  the  heater  is  a  compromise  between  what  should  be  and  what 
is  needed. 

The  length  of  the  pipes  to  the  various  rooms  should  be  as 
short  as  possible,  but  here  again  the  demands  of  the  owner  must 


250 


ELEMENTS  OF  HEATING  AND  VENTILATION 


be  considered.      Thus  for  room  5,  the  pipe  could  have  been 
made  shorter  had  the  use  of  room  permitted  the  register  to  be 


FIG.  177. — Pipe  and  Heater  Arrangement. 


2ND  FLOOR  1ST  FLOOR 

FIG.  178. — Arrangement  of  Outlets. 

placed  near  the  partition.     Fig.   178  shows  the  location  and 
size  of  the  registers  and  flues. 


FURNACE  HEATING 


251 


The  application  of  the  foregoing  principles  to  the  house 
gives  the  results  in  the  following  table: 


I 

C4 

Venti- 
lation. 

Leader. 

Stack 

Register. 

Vent  Stacks. 

Vent  Registers. 

Area 

Size. 

Area 

Size. 

Area. 

Size. 

Area 

Size. 

Area 

Size. 

I 

2 

3 
4 
5 
6 

7 
8 

1  9 

10 
ii 

12 

14000 
9600 
1450 
5700 
7300 
8900 
11700 
7300 
1800 
6400 
7000 
2400 

1  80 
123 
19 
73 
93 
114 

100 

63 
17 
57 
60 

23 

15 
13 

5 

10 

ii 

12 

(12)  10 
9 
(5)8 
9 
9 
(6)  10 

233 
160 

24 
95 

122 
148 
(I96) 
122 
(30) 
107 

116 

(40) 

15X16 
10X16 

10X10 
10X14 
10X16 
12X12 

10X12 

10X10 

10X12 
10X12 
10X12 

125 
83 
13 

52 
65 
80 

(76) 
48 

12 
40 
46 

(16) 

2-4X14 
2-4  X   8 

1  88 
128 

19 
76 

98 
118 

157 
98 
24 
86 
93 
32 

2-10X12 
I-IOXI2 

1-10X10 
1-10X10 

2-IoXlO 
2-IOXIO 

1-10X10 

1-10X10 
1-10X10 

1-4X12 
1-4X14 
2-4X10 
2-4X12 
1-4X12 

4X10 
4X12 

(95) 
60 

IS 
52 
57 
(20) 

-4X14 
-4X14 
-4X12 
-4X13 
-4X14 
1-4X14 

The  first-floor  heat  registers  are  all  of  the  floor  form.  The 
register  is  omitted  from  room  3  owing  to  the  small  size.  The 
heat  for  rooms  7  and  12  is  divided  between  two  registers,  that 
in  room  12  being  made  larger  than  necessary  for  this  room. 
It  is  placed  near  the  door  of  room  7  so  that  the  heat  enters 
that  room. 

It  will  be  seen  in  the  table  that  4X14"  is  the  limiting 
size  of  stacks.  In  the  actual  construction  no  vents  were  used 
extending  to  the  attic.  The  table,  however,  is  made  to 
include  these  so  as  to  illustrate  the  method.  In  Fig.  178  the 
position  of  registers  and  stacks  is  shown.  The  remaining 
computation  is  that  for  the  cold-air  supply  and  recirculated  air 
supply. 

Of  the  air  supply  of  83,550  cu.ft.  at  70°  F.  30,000  enters  as 
cold  air  at  o°  as  leakage  and  the  full  80,000  passes  back  as 
recirculated  air  at  70°.  The  area  of  the  circulating  ducts  using 
a  low  velocity  of  4  ft.  per  second  will  be 


5l  sq.ft. 


252          ELEMENTS  OF  HEATING  AND  VENTILATION 
The  register  faces  should  be 

si 


0.66 


=  8J  sq.ft. 


The  house  is  planned  to  have  one  register  under  the  stairs  of 
6  sq.ft.  connected  to  4  sq.ft.  of  flue  and  one  register  of  3!  ft.  in 
the  corner  of  room  i,  connected  to  a  flue  of  2  sq.ft.  The  cold 
air  when  needed  enters  as  shown  in  Fig.  177.  The  area  of 
the  cold-air  opening  was  i\  sq.ft.  This,  however,  is  rarely 
needed. 

The  use  of  the  jib  panel  of  a  stairway  as  the  place  for  the  reg- 
ister of  the  recirculating  flue  is  excellent.  It  is  better  than  one  in 
the  hall  floor  in  that  it  is  not  conspicuous  and  does  not  collect 
dirt,  nor  does  it  form  an  unpleasant  place  over  which  one  must 

walk.  The  return  duct  must  be 
of  ample  size  and  it  must  lead  into 
the  base  of  the  heater  by  easy 
curves. 

In  all  cases  the  air  supply  must 
be  ample  if  the  heater  is  to  per- 
form its  duty.  Had  the  80,000 
cu.ft.  been  introduced  trom  the 
outside,  the  area  required  would 
have  been 


80000X0.87 
4X3600 


=  5  sq.ft. 


This  air  supply  may  be  filtered 
by  passing  it  through  cheesecloth 
or  by  passing  it  over  a  series  of 
baffles  as  shown  in  Fig.  179,  the 


FIG.  179. — Baffle  Screens. 

area  of  the  various  parts  being  sufficient  for  the  passage  of  the 


air. 


Some  designers  proportion  the  cold-air  duct  by  the  total 
area  of  the  leader  pipes.  This  method  can  be  used,  but  it  is 
just  as  well  to  figure  it  from  the  amount  of  air  to  be  handled. 


FURNACE  HEATING  253 

The  cold-air  inlet  should  always  be  placed  on  the  side  toward 
the  prevailing  winds. 

The  size  of  the  fire  pot  is  found  at  this  point,  although  really 
belonging  to  the  next  chapter.  From  the  heat  to  be  developed 
as  found  in  the  first  part  of  this  chapter  the  total  heat  with  the 
leakage  air  to  be  cared  for  is  144,000  B.t.u.  per  hour.  If  the 
efficiency  of  the  furnace  is  taken  at  60  per  cent  and  the  rate  of 
burning  coal  is  4  Ibs.  per  square  foot,  the  area  of  the  grate  is 

144000X144 
=        t 


0.60X14000X4 


This  matter,  with  the  size  of  the  smoke  flue,  will  be  further  con- 
sidered in  the  next  chapter.  In  figuring  the  pipes,  furnaces  and 
other  parts  for  a  room,  some  designers  and  manufacturers  reduce 
the  heat  quantity  to  equivalent  glass  surface  while  others  find 
equivalent  volume  in  cubic  feet. 

Now  Carpenter's  approximate  rule, 

W 

4 

(p.  69)  shows  that  4  sq.ft.  of  wall  is  equivalent  to  i  sq.ft.  of 
glass  and  for  one  change  of  air  per  hour  each  50  cu.ft.  of  volume 
is  equal  to  i  sq.ft.  of  glass.  Hence  if  one-fourth  of  the  wall 
area  in  square  feet  and  one-fiftieth  of  the  volume  in  cubic  feet 
times  the  changes  per  hour  are  added  to  the  glass  area  the  result 
is  called  the  equivalent  glass  area.  In  some  methods  the  ven- 
tilation term  is  omitted  and  the  floor  and  ceiling  are  added  in 
giving  the  equivalent  glass  as  equal  to  the  glass  plus  one-quarter 
the  wall  area  and  one-twentieth  of  the  area  of  the  floor  or 
ceiling  to  care  for  losses  to  basement  or  attic  in  first-floor  or  top- 
floor  rooms.  The  equivalent  is  then  multiplied  by  the  heat  loss 
per  square  foot  of  glass  to  find  the  total  heat  loss.  This  glass  loss 
is  about  70  B.t.u.  per  square  foot  per  hour. 

In  one  of  the  equivalent  cubic  feet  methods  the  actual 


254  ELEMENTS  OF  HEATING  AND  VENTILATION 

cubic  feet  are  increased  by  75  cu.ft.  for  each  square  foot  of 
glass  surface  and  8  cu.ft.  for  each  square  foot  of  wall  space. 
This  rule  shows  that  the  changes  per  hour  are  i^,  and  that  the 
allowance  for  wall  area  is  not  nearly  sufficient. 

In  both  of  these  methods  allowance  is  made  for  exposure, 
10  per  cent  being  added  on  the  north  and  west  sides. 

Certain  manufacturers  list  pipes  and  heaters  to  care  for 
equivalent  cubic  feet  or  square  feet,  and  these  may  be  used  in 
designing.  These  methods  are  all  equivalent  to  the  theoretical 
one  given  in  the  text,  but  they  are  not  as  valuable,  as  the  work 
is  too  empirical. 

The  methods  used  in  calculation  for  any  form  of  building 
are  similar  to  the  above. 

When  distant  rooms  are  to  be  heated-  a  combination  system 
is  sometimes  used  in  which  the  distant  rooms  are  heated  by  hot 
water  furnished  by  a  coil  or  cluster  in  the  fire  box  of  the  furnace, 
as  will  be  shown  later.  The  method  of  determining  the  size 
of  flow  pipes,  radiators  and  various  parts  of  this  system  have 
been  discussed  in  previous  chapters. 


CHAPTER  X 

FURNACES  AND  BOILERS 

THE  ordinary  hot-air  furnace,  Fig.  180  (Graff  Co.'s  Lacka- 
wanna  Furnace)  consists  of  an  ash  pit,  A,  a  fire  pot,  B,  a  radiator 


FIG.  180. — Graff  Lackawanna  Furnace. 

C  and  within  the  radiator  the  combustion  chamber.  The  radiator 
may  be  made  of  sheet  steel  between  cast  heads  as  shown,  or  it 
may  be  of  cast  iron,  Fig.  181  (Graff-Comfort  Furnace).  The 

255 


256 


ELEMENTS  OF  HEATING  AND  VENTILATION 


plan  of  radiator  is  illustrated  in  Fig.  182.  The  gases  enter  the 
dome  over  the  combustion  chamber,  which  contracts  in  the  form 
of  a  dome  and  is  connected  to  the  center  portion  of  the  radiator. 
The  hot  gases  thus  pass  around  the  radiator  to  the  smoke 
outlet.  In  most  cases  there  is  a  by-pass  valve  or  cut-off  plate 
which  on  being  moved  gives  a  free  passage  from  the  fire  pot 


FIG.  181.— Graff  Comfort  Heater. 


to  the  smoke  outlet  to  be  used  on  starting  fires.  The  base  ring 
D  of  the  furnace  is  placed  on  the  brick  foundation  which  in  many 
cases  forms  the  cold-air  pit  to  which  the  air  supply  is  brought 
from  the  atmosphere  or  house.  A  central  pier  is  usually  built 
to  carry  the  weight  of  the  ash  pit,  fire  box  and  radiator.  The 
grates  are  mostly  made  of  triangular-shaped  toothed  bars, 
Fig.  183,  supported  on  their  ends  and  so  arranged  that  by 
turning  one  of  the  bars  of  the  grate,  one-half  of  them  turn, 


FURNACES  AND  BOILERS 

Clean  Out 


257 


Feed 


FIG.  182. — Plan  of  Furnace  Radiator. 


FIG.  183.— Grate  and  Ash  Pit  of  Fuller,  Warren  &  Co. 


258 


ELEMENTS   OF  HEATING  AND   VENTILATION 


cutting  clinkers  and  allowing  clinkers  and  ashes  to  fall.  A  gal- 
vanized-iron  casing  is  now  placed  around  the  furnace  and  is 
carried  up  to  the  bonnet.  This  casing  should  be  of  bright  iron 
to  cut  down  the  radiation  loss  and  in  some  cases  it  is  made  double 
with  an  air  space  for  this  purpose. 

The  air  duct  leading  to  the  pit  beneath  the  furnace  is  made 
of  brick  or  concrete  and  is  covered  by  wood  or  reinforced  con- 
crete, Fig.  184.  In  case  the  concrete  form  is  used  manholes 
should  be  left  for  cleaning  or  examination. 


*  FIG.  1 84.— Cold-air  Ducts. 

The  main  objection  to  the  type  of  furnace  shown  in  Figs, 
1 80,  181,  which  is  probably  the  most  common  form,  is  the 
fact  that  the  heating  surface  is  not  sufficiently  large  for  the  grate 
area.  To  increase  the  heating  surface  in  their  heater,  the  Graff 
Co.  in  their  "  Faultless  Furnace,"  use  a  number  of  air-heating 
flues,  Fig.  185,  which  are  surrounded  by  the  hot  gases  and  are 
exposed  to  the  radiant  heat  and  through  which  the  air  passes. 
The  hot  gases  pass  through  openings  at  the  top  of  these  air-heat- 
ing flues  to  the  exterior  surface  and,  by  means  of  the  baffle 
plates,  have  a  long  path  to  the  smoke  outlet,  giving  up  their 
heat  to  the  walls  of  the  boxes.  The  outside  of  this  hot-^as 


FURNACES  AND  BOILERS 


259 


260 


ELEMENTS   OF  HEATING  AND  VENTILATION 


passage  is  made  of  sheet  iron  and  this  serves  as  the  outer  surface 
of  the  radiator.     The  casing  is  placed  outside  of  this  so  that 


FIG.  1 86. — Kelsey  Warm-air  Generator. 


FIG.  187.— Tubes  in  Radiator. 

this  furnace  has  much  the  same  appearance  as  the  Lackawanna 
furnace  of  this  company. 


FURNACES  AND  BOILERS  261 

The  fins  guiding  the  air  into  the  air-heating  flues  also  add 
heating  surface. 

The  Kelsey  warm-air  generator  or  furnace,  Fig.  186,  shown 
with  a  hot-water  generator  at  the  top  of  the  combustion  chamber, 
is  quite  similar  to  the  Graff  furnace.  In  this  the  air-heating 
flues  or  elements  are  made  corrugated  to  increase  the  heating 
surface.  The  action  of  this  furnace  is  similar  to  that  just 
examined. 

The  same  result  may  be  accomplished  partially  by  putting 
tubes  through  the  hot  gas  space  of  the  radiator,  Fig.  187,  and 
allowing  the  air  to  pass  through  the  tubes  while  the  gases  pass 
around  them.  This  method  should  improve  the  efficiency  of 
the  heater.  This  figure  illustrates  the  method  of  putting  the 
casing  together  and  the  bonnet.  The  three  castings  forming 
the  ash  pit,  fire  pot,  and  dome  of  fire  box  are  clearly  seen.  These 
sections  are  fitted  together  by  the  edge  of  one  casting  fitting 
in  a  groove  in  the  other,  which  joint  is  filled  with  a  stove  cement, 
making  it  tight.  The  same  substance  is  used  in  putting  the 
sections  of  the  other  furnaces  together.  It  is  important  that 
this  work  be  carefully  done,  as  a  leak  of  coal  gas  might  poison 
the  occupants  of  the  house.  The  top  of  the  furnace  is  often 
covered  with  sand  to  cut  down  the  radiation  from  the  top  and 
a  sand  ring  is  placed  at  the  edge  of  flat  tops  to  hold  this. 

Fig.  1 88  is  the  special  Novelty  Furnace  of  the  Abram  Cox 
Stove  Co.  in  which  the  increased  heating  surface  is  obtained  by 
complex  castings  of  considerable  length.  The  method  of  making 
gas-tight  joints  is  illustrated  as  well  as  the  use  of  a  double 
casing.  The  direct  draft  for  cutting  down  the  resistance  is  shown 
near  smoke  outlet  and  the  water  pan  near  the  bottom  at  B.  The 
water  pan  should  be  installed  on  all  hot-air  furnaces  to  humidify 
the  air,  giving  it  the  necessary  amount  of  moisture.  The  pan 
should  be  located  where  it  will  not  be  in  contact  with  the  hot 
air,  as  that  air  could  take  up  so  much  moisture  that  this  would 
be  deposited  on  furniture  and  windows  when  cooled  to  the  room 
temperature.  It  is  usually  placed  near  the  bottom  of  the  fur- 
nace where  the  air  temperature  and  consequently  the  moisture 
content  is  not  high. 


262 


ELEMENTS   OF  HEATING  AND  VENTILATION 


Sectional  heaters  or  boilers,  Fig.   189,  are  used  for  either 
hot  water  or  steam.     They  are  made  of  sections  which  may  be 


FIG.  1 88.— Special  Novelty  Heater. 

t 

increased  in  number  to  form  heaters  of  different  capacities. 
The  middle  sections  are  the  same  in  form  except  for  side  or  top 
outlets,  while  special  shapes  of  sections  form  the  rear  and  front. 
The  sections  are  so  made  that  there  is  a  large  amount  of  surface 


FURNACES  AND  BOILERS 


263 


exposed  to  the  fire.     This  is  done  by  having  considerable  space 
between  the  lower  parts  of  the  sections,  although  at  the  top  the 


FIG.  189.— No.  5-15-6  Ideal  Sectional  Boiler. 

sections  come  so  closely  together  that  three  passages  are  formed 
through  which  the  gases  must  pass  to  the  chimney.  The 
sections  of  the  boiler  shown,  the  Ideal  Sectional  Boiler  of  the 


264 


ELEMENTS  OF  HEATING  AMD  VENTILATION 


American  Radiator  Co.,  are  held  together  by  bolts,  the  sec- 
tions being  connected  by  three  conical-faced  push  nipples. 
The  sections  A,  Fig.  190,  are  supported  by  the  casting  forming 
the  grate  and  ash  pit.  Some  other  boilers,  as  the  American 
of  the  Pierce  Co.,  B,  Fig.  190,  are  made  of  sections  which  are  con- 
nected by  three  manifolds,  attached  to  flanged  nipples  screwed 
in  at  a,  b  and  c.  The  Ideal  Boiler  has  an  outlet  at  the  top  and 
the  bottom  as  shown  in  the  figure  for  steam  or  water  and 
feed.  The  steam  boilers  are  usually  provided  with  damper 
regulators  which  are  attached  as  shown  to  the  damper  and 


o 


FIG.  190. — Sections  of  Boiler. 

ash-pit  door.  They  are  operated  by  the  pressure  in  the  steam 
boiler  and  shut  draft  and  ash-pit  doors  when  the  pressure 
rises,  while  at  low  pressures  both  are  opened.  Fig.  189 
shows  the  equipment  on  one  of  these  used  as  a  steam  boiler. 
Fig.  195  illustrates  the  dimensional  sheet  of  one  type  of  this 
boiler,  the  table  of  which  will  be  of  service  in  laying  out 
plans  before  lettng  contracts.  For  small  installations  small 
circular  boilers  are  used.  Several  of  these  are  illustrated  in 
Fig.  191.  A  represents  the  Pierce  Boiler,  in  which  the  sec- 
tions are  united  by  screwed  nipples.  The  water  leg  on  the 
side  of  the  fire  box  forms  a  good  heating  surface.  The  outlet 
for  steam  (or  water)  is  at  the  top,  while  the  return  enters  at 
the  bottom. 


FURNACES  AND  BOILERS 


265 


266 


ELEMENTS  OF  HEATING  AND  VENTILATION 


The  Spence  water  boiler,  as  shown  at  B,  Fig.  191,  consists 
of  five  cast  circular  sections  attached  to  the  base  section  by  a 
cast  manifold  on  one  side.  The  manifold  is  so  made  that  there 
is  continuous  circulation  from  the  bottom  to  the  top,  in  a  definite 
path  as  shown  by  the  arrows.  C  illustrates  the  Ideal  Junior 
Water  Heater  of  the  American  Radiator  Co-  used  for  heating 


FIG.  192. — Humphrey  Heater. 

water  for  laundry  purposes  or  domestic  service.  This  is  not 
large  and  is  intended  to  be  used  when  a  quantity  of  hot  water 
is  needed  in  the  laundry  or  home.  However,  the  gas  heater 
has  come  into  extensive  use  where  hot  water  is  needed  for  domestic 
service.  There  are  a  number  of  these  heaters  on  the  market. 
The  Humphrey  Gas  Water  Heater  is  shown  in  Fig.  192.  The 
gas  burners  A  are  supplied  through  pipe  B.  The  small  pipe  C 
supplies  gas  to  the  small  pilot  light  D.  The  pilot  light  can  be 


FURNACES  AND  BOILERS 


267 


shut  off  by  the  valve  at  the  top  of  the  line  C  and  the  main  gas 
line  may  be  closed  by  a  cock. 

The  two  water  lines  are  behind  the  gas  line.  The  cold  water 
from  the  city  supply  or  cool  water  from  the  storage  tank  enters 
at  the  bottom  of  the  coils.  The  water  circulates  from  the  tank 
as  soon  as  water  is  not  taken  from  the  faucets  by  an  automatic 

Hot  Water. 


AA' 


FIG.  193. — Rudd  Heater  and  Tank. 

valve  which  allows  cold  city  water  to  enter  when  a  faucet  is 
open.  When  the  water  from  the  tank  reaches  140°  F.,  a  ther- 
mostat cuts  off  the  gas  supply  except  for  the  pilot  light.  As 
soon  as  cold  water  is  used  this  thermostat  turns  on  the  gas 
supply.  The  Rudd  Heater  which  is  somewhat  similar  to  this 
is  also  a  good  one  to  give  an  instantaneous  supply  of  hot 


268 


ELEMENTS  OF  HEATING  AND  VENTILATION 


water.  The  demand  for  gas  is  so  great  in  these  heaters  that 
special  services  are  often  run  for  them.  Fig.  193  illustrates  the 
attachment  of  one  of  these  heaters  to  a  storage  tank  with 
the  thermostat  attached  to  the  gas  supply  at  one  end  of 
the  tank. 

For  small  plants  where  steel  boilers  are  needed  on  account 
of  a  desire  for  high-pressure  steam  a  locomotive  type  of  small 
boiler,  Fig.  194,  may  be  employed.  This  is  the  Acme  Boiler  of 
the  American  Radiator  Co.,  and  they  are  built  from  about  10  to 
100  H.P.  For  large  plants  the  water-tube  or  fire-tube  boilers 
are  used  and  these  are  considered  in  books  on  steam  boilers 
and  do  not  form  a  part  of  this  work.  For  guidance  of  the  student 


FIG.  194. — Locomotive  Type  of  Boiler. 

the  following  tables  of  a  few  standard  furnaces  and  boilers  are 
appended.  Every  engineer  should  have  a  supply  of  catalogues 
giving  dimensions,  sizes  and  capacities  of  various  kinds  of  appa- 
ratus. The  hot-air  furnaces  are  rated  by  the  cubic  feet  of  volume , 
equivalent  cubic  feet  or  equivalent  square  feet  of  glass  which  the 
heater  will  care  for.  The  hot-water  and  steam  boilers  are  rated 
in  square  feet  of  radiation  which  the  boiler  will  supply  with 
heat.  This  includes  the  square  feet  of  surface  in  radiators  and 
piping  combined.  The  numbers  are  the  result  of  tests  and  in  the 
catalogue  of  the  American  Radiator  Company,  they  are  found 
by  taking  four  times  the  steam  produced  by  the  boiler  per 
hour  on  a  test  in  which  the  fire  box  has  to  be  charged  once 


FURNACES  AND  BOILERS 


269 


in  eight  hours.  The  allowance  for  piping  should  be  made 
even  though  the  pipes  be  covered.  The  piping  in  the  ordi- 
nary direct  system  for  steam  amounts  to  about  25  per  cent 
of  the  radiator  surface,  while  in  hot-water  work  the  amount 
is  from  30  to  50  per  cent. 

DIMENSIONS  AND  CAPACITY  OF  SPECIAL  NOVELTY  HEATERS 


Capacity  in 

"Equivalent 

Cubic  Feet" 

Heater  will 

S:_  -.  f.f 

'No. 

Heat,  on  the 
Basis  of  Main- 
taining a  Tem- 
perature of  70° 
Above  Zero  in 
the  Building 

Height  of 
Heater 
Cased 
Complete. 
Inches. 

Diameter 
of  Fire- 
pot, 
Inches. 

Diameter 
of 
Casings, 
Inches. 

Height 
to  Top  of 
Radia- 
tor, 
Inches. 

Diame- 
ter of 
Smoke 
Pipe, 
Inches. 

Weight, 
Less 
Casings, 
Pounds. 

ize  ot 
Cold-air 
Duct 
Re- 
quired, 
Inches. 

when  the  Out- 

side Tempera- 

ture is  Zero.* 

732 

32000 

62 

19 

32 

50 

7 

820 

10X20 

736 

41000 

64 

21 

36 

52 

8 

1060 

12X20 

740 

50000 

65 

23 

40 

53 

8 

1280 

12X26 

744 

6lOOO 

66 

26 

44 

56 

9 

1675 

12X32 

748 

73000 

67 

28 

48 

57 

9 

2125 

14X32 

752 

76000 

68 

28 

52 

58 

9 

2270 

14X33 

756 

105000 

70 

32 

56 

60 

9 

2850 

14X48 

*For  definition  of  "Equivalent  Cubic  Feet"  see  p.  254. 


DIMENSIONS  AND  HEATING  CAPACITY  OF  FULLER,  WARREN  & 
CO.'S  B  SERIES  FURNACES 

(Similar  to  Fig.  180  but  with  steel  radiator). 


Size. 

Diameter 
Firepot, 
Inches. 

Diameter 
Casing. 
Inches. 

Height 
Furnace, 
Inches. 

Recom- 
mended 
Size  of  Air 
Box. 

Diameter 
Smoke 
Pipes. 
Inches. 

Number 
of  Aver- 
age Size 
Hot-air 

Diameter 
of  Single 
Hot-air 
Pipe. 

Pipes. 

Inches. 

B  18-32 

18 

32 

46f 

10X15 

7 

3  to    4 

2O 

B  20-36 

20 

36 

Sol 

10X22 

7 

4  to    5 

22 

B  22-42 

22 

42 

5i* 

12X25 

8 

5  to    7 

26 

B  24-48 

24 

48 

54i 

13X28 

8 

6  to    8 

28 

B  26-53 

26 

53 

56i 

14X32 

8 

7  to    9 

30 

B  28-58 

28 

58 

58! 

14X35 

10 

9  to  ii 

32 

B  31-60 

31 

60 

S9l 

14X45 

10 

II  tO  12 

36 

B  36-65 

35 

65 

61 

16X42 

IO 

12  to  15 

40 

270 


ELEMENTS  OF  HEATING  AND   VENTILATION 


DIMENSIONS  AND  HEATING  CAPACITIES,  GRAFF  FAULTLESS 

HEATER 


Height 

Heat- 

Usual 

Cubic  Feet 

Size. 

Diam. 
Firepot 

Diam. 
Casing. 

Height, 
Casing. 

with 
Cone 
Top 

Grate 
Area, 
Sq.ins. 

No.  of 
Flues. 

ing 
Sur- 
face, 

Cold 
Air 

Capacity. 

Casing. 

Sq.ft. 

Houses 

Halls 

19-48 

19 

48 

48 

66 

283 

9 

131 

12X36 

15000 

25000 

22-54 

22 

54 

54 

69 

380 

10 

152 

14X40 

25000 

45000 

25-60 

25 

60 

60 

70 

491 

ii 

I76 

14X48 

40000 

60000 

30-70 

30 

70 

70 

70 

707 

12 

219 

16X60 

60000 

IOOOOO 

DIMENSIONS  AND  HEATING  CAPACITIES— KELSEY  WARM-AIR 
GENERATORS 


Regular 

Square 

Size 

Genera- 
tor. 

Diameter 
of  Base, 
Inches. 

Height  of 
Castings, 
Inches. 

Height 
Generator. 
Cased  Com- 
plete, 

Diameter 
Grate, 
Inches. 

Area  of 
Grate, 
Square 
Feet. 

Heating 
Surface, 
Square 
Feet. 

Feet 
Heating 
Surface  to 
Each  Square 

Foot  of 

Grate  Area. 

24 

56 

59 

69 

24 

3 

161 

51 

27 

60 

60 

72 

27 

4 

I76 

44 

3° 

64 

64 

76 

30 

5 

211 

43 

Ciihir 

Inside 

Thickness 

Dimen- 

Size 
Genera- 
tor. 

Free  Area 
Square 
Feet. 

Heated 
per 
Minute 

Cubic  Feet 
Air  Heated 
per  Minute 
Gravity. 

of  Brick 
Walls, 
Heater 
Case. 

sions, 
Brick 
Housing 
One 

Size  of 
Smoke 
Pipe. 
Inches. 

Weight  with 
Cast 
Casing. 

ical 

Inches. 

Heater. 

3  Inches. 

24 

4 

2800 

1900 

8 

54X68 

9 

2520 

27 

5 

3500 

2300 

8              57X70 

9 

2975 

30 

6 

4100 

2900 

8             60X72 

9 

3425 

I 

The  ratings  in  the  following  table  for  boilers  are  for  hard 
coal.  With  soft  coal  use  one  size  larger  than  tabular  value. 
Ratings  include  all  pipes,  covered  or  uncovered.  These  amount 
to  about  30  per  cent  of  radiator  surface.  The  width  of  the 
grate  is  equal  to  the  number  of  the  boiler;  15,  22,  28,36  and  48 
represent  the  grate  width.  The  length  is  the  length  of  the 
fire  box. 


FURNACES  AND  BOILERS 


271 


LEADING  DIMENSIONS,  IDEAL  HEATERS  FOR  STEAM  AND 
HOT  WATER 


Num- 
ber and 
Sec- 
tions. 

Length, 
Total. 

Height, 
Total. 

Width, 
Total. 

Water 
Line. 

Firepot 

Out- 
let. 
Ins. 

Smoke 
Pipe. 

Square  Feet 
Capacity. 

Steam 

Water 

Steam 

Water 

Steam. 

Water. 

15-4 

4o| 

fci 

4*1 

38| 

27^ 

38i 

19X18 

2-3 

8 

300 

500 

15-5 

47i 

6r| 

42^ 

38f 

*7l 

381 

19X25 

2-3 

8 

425 

700 

I5-6 

53t 

6ij 

42* 

38! 

27* 

38i 

19X31 

2-3 

8 

550 

900 

22-5 

53i 

67l 

52i 

45i 

36 

45 

25X28 

2-4 

IO 

800 

1300 

22-6 

6oi 

67* 

521 

45i 

36 

45 

25X35 

2-4 

10 

IOOO 

1650 

22-7 

.67* 

67i 

52i 

45i 

36 

45 

25X42 

3-4 

10 

1200 

2000 

22-8 

74i 

67i 

52i 

45i 

36 

45 

25X49 

3-4 

10 

I40O 

2350 

28-5 

60 

75f 

6of 

53^ 

44 

52 

33X32 

2-4 

12 

1300 

2150 

28-6 

68 

75l 

6o| 

53i 

44 

52 

33X40 

2-4 

12 

1625 

2675 

28-7 

76 

75t 

6of 

53l 

44 

52 

33X48 

3-4 

12 

1950 

3200 

28-8 

84 

75i 

6of 

53* 

44 

52 

33X56 

3-4 

12 

2275 

3725 

36-5 

69f 

83 

70 

64 

53i 

60 

41X36 

2-5 

IS 

2IOO 

3450 

36-6 

78f 

83 

70 

64 

53i 

60 

41X45 

2-5        15 

2625 

4325 

36-7 

00 

oo 

83 

70        64 

53i 

60 

41X54 

3-5        15 

3150 

5200 

36-8 

97i 

83 

70 

64 

53i 

60 

41X63 

3~5 

15 

3675 

6050 

36-9 

106^ 

83 

70 

64 

53* 

60 

41X73 

4-5 

15 

42OO 

6925 

48-6 

92 

97 

8i| 

80 

68 

70 

50X53 

2-6 

21 

4750 

7825 

48-7 

102!  i  97 

8if 

80 

68 

70 

50X64 

2-6 

21 

5700 

9400 

48-8 

114 

97 

8if 

80 

68 

70 

50X75 

3-6 

21 

6650 

10975 

48-9 

1241 

97 

8if 

80 

68 

70 

50X86 

3-6 

21 

7600 

!2550 

48-10 

135        97 

8if 

80 

68 

70 

50X90 

3-6 

21 

8550 

14125 

The  dimensions  in  this  and  the  following  table  will  be  found 
to  be  approximately  the  same  for  other  makes  of  sectional  boilers 
and  for  that  reason  no  other  tables  will  be  given. 

In  finding  the  size  of  a  hot-air  furnace  one  method  is  to  find 
the  amount  of  heat  for  the  heat  loss  and  for  the  heating  of 
the  ventilating  air  up  to  70°  and  to  divide  this  by  the 
product  of  the  efficiency  of  the  furnace  and  the  heating  value 
of  the  coal  and  the  result  is  the  amount  of  coal  required 
per  hour.  This  is  then  divided  by  the  rate  of  combustion, 
pounds  of  coal  per  square  foot  per  hour,  to  find  the  area  of  the 
grate. 


272          ELEMENTS  OF  HEATING  AND  VENTILATION 


FIG.  195. — Dimensional  Views  of  Sectional  Boiler. 


DIMENSIONS    OF    IDEAL    BOILERS    OF    THE    AMERICAN 
RADIATOR  CO. 


Size. 

A 

B 

C 

D 

£ 

F 

G 

E 

1 

15"  boilers..  . 

28* 

46A 

13* 

4i| 

34l 

I2i 

i8f 

25 

22"   "  ... 

36! 

S2l 

isi 

47l 

40^ 

14! 

21} 

28| 

28"   "  ... 

44^ 

6of 

i8i 

ssl 

46i 

16 

24 

32 

36"   "  ... 

54* 

69! 

2!H 

63! 

5«A 

i8i 

27f 

36i 

48"   "  ... 

69 

8ii 

27i 

73l 

59i 

ail 

32i 

43 

Size. 

7 

/ 

^ 

^ 

0 

P 

5 

T 

15"  boilers..  . 

r6A 

23! 

8X14 

"I 

61 

8 

i3i 

7i 

22"   "  ... 

i6i 

29! 

8X14 

9^ 

7i 

10 

14! 

8i 

2,S"    "   ... 

I7i 

37* 

9X18 

10 

8 

12 

16 

9i 

36"   "  ... 

i8A 

45T6 

10X20 

ioH 

9l 

15 

i8A 

ioi 

48"   "  ... 

22f 

581 

11X19 

I4H 

io| 

21 

I7f 

I2| 

For  X,  C/",  and  M  see  previous  table. 

If  H= heat  loss  per  hour; 

Vi  =  leakage  air  in  cubic  feet  at  70°  per  hour; 
/r  =  room  temperature; 


FURNACES  AND  BOILERS  273 

t0  =  outside  area; 

//  =  heat  per  pound  of  coal  in  B.t.u.; 
eff.  =  efficiency  of  furnace  =  65  per  cent; 
O  =  rate  of  combustion  =  4  or  5  Ibs.; 
A  =area  of  grate. 

.02Vi(t,-t0) 


This  area  should  be  compared  with  the  area  of  the  manufac- 
turer's heater  for  the  same  volume  of  building.  The  results 
should  be  approximately  the  same. 

For  some  large  buildings  the  area  will  be  found  to  be  greater 
than  the  amount  to  be  obtained  from  the  largest  heater.  In 
that  case  two  or  more  heaters  must  be  used.  These  may  be 
placed  at  convenient  locations  in  the  cellar,  thus  shortening 
runs  and  making  the  heating  more  positive  if  it  is  possible  to 
have  proper  chimneys,  although  in  some  cases  twin  furnaces  or 
batteries  have  to  be  used.  In  this  method  several  furnaces  are 
placed  side  by  side  and  a  common  bonnet  is  used  connecting 
all  casings  (Fig.  176).  This  of  course  has  the  advantage  over 
the  separate  arrangement  of  allowing  one  to  run  a  single  furnace 
at  full  capacity  when  a  small  amount  of  heat  is  needed  in  the 
early  or  late  heating  season. 

The  application  of  this  method  to  the  residence  of  Chap. 
V  gives  the  following  area: 

i  St.  From  heat  required: 

Total  heat  =  144000; 

144000 

Grate  area  =     ,   ^       —  —  —  =  620  sq.in. 
0.60X14000X4 

Diam.  grate  =  28  ins. 
2d.  By  method  of  volume: 

Total  volume  =  27600  cu.ft.;  use  25-60  Graff. 
Diam.  grate  25  ins.  (Graff  table). 


274          ELEMENTS  OF  HEATING  AND  VENTILATION 
3d.  By  method  of  equivalent  volumes: 


Room. 

75  X  Glass. 

8  X  Wall. 

Volume. 

Total  Equivalent 
Volum^ 

I 

Q,IOO 

2,250 

3,no 

14,460 

2 

8,000 

2,700 

2,160 

I2,86o 

3 

2,IOO 

750 

400 

3,250 

4 

2,600 

1,540 

i,390 

5,530 

5 

3,600 

1,550 

1,620 

6,770 

6 

5,850 

620 

2,  IIO 

8,580 

7 

6,4OO 

2,400 

2,9IO 

II,7IO 

8 

3,600 

1,  680 

2,OOO 

7,280 

9 

750 

390 

720 

1,  860 

10 

3^50 

1,520 

I,7OO 

6,370 

ii 

3,150 

1,620 

I,7IO 

6,480 

12 

1,650 

300 

480 

2,43° 

Total  

49,95O 

17,320 

20,310 

87,580 

This  requires  a  No.  752  Special  Novelty  Heater  with  28-in.  fire  pot. 

In  selecting  a  furnace  the  endeavor  should  be  made  to  get 
as  much  heating  surface  per  square  foot  of  grate  surface  as  pos- 
sible. There  are  certain  furnace  books  which  state  that  unless 
the  galvanizing  is  burned  off  of  the  smoke  pipe  the  furnace  has 
not  been  operated  to  its  full  capacity.  This  burning  means 
a  high  temperature  of  the  exhaust  gases  and  hence  a  great  loss 
in  them.  There  should  be  enough  surface  to  remove  the  heat 
before  these  gases  leave  the  furnace.  The  flue  will  be  hot  in  the 
coldest  weather,  but  this  is  no  proof  that  the  furnace  is  working 
properly.  The  furnace  giving  the  lowest  temperature  of  exhaust 
gases,  other  things  being  equal,  is  always  the  best  furnace.  The 
Kelsey  and  Graff  furnaces  give  ratios  of  heating  surface  to  grate 
surface  of  45  :  i,  and  the  student  should  have  this  in  mind  as 
a  possible  ratio.  In  steam-boiler  work  35  to  40  is  the  value 
often  used. 

The  flue  leading  from  the  furnace  to  the  chimney  is  usually 
fixed  by  the  size  of  the  fire  pot  or  the  capacity  of  the  furnace. 
An  area  of  one- twelfth  of  the  grate  for  furnaces  and  one-eighth 
of  the  grate  area  for  small  boilers  may  be  used,  although  the 
method  employed  by  many  manufacturers  is  to  use  a  table 
which  gives  the  B.t.u.  cared  for  by  various  sizes  of  flue. 

The  chimney  should  be  at  least  30  to  40  ft.  high  and  the  chim- 


FURNACES  AND  BOILERS  275 

ney  flue  if  round  should  be  2  ins.  larger  in  diameter  than  the 
smoke  pipe,  while  if  square  the  size  of  the  square  is  i^  ins.  larger 
than  the  diameter  of  the  smoke  pipe  or  flue.  If  the  chimney 
flue  is  rectangular  the  dimensions  b  and  d  should  be  such  that 

bd 

— — — —  =  or  >  J  side  of  square  of  desired  size. 

The  inside  of  the  flue  should  be  as  smooth  as  possible  and 
tight.  It  is  well  to  line  it  with  tile  for  fire  protection,  the  space 
between  tile  and  brick  being  filled  with  mortar.  This  chimney 
can  then  be  built  of  4-in.  brick  work,  while  an  unlined  flue  must 
be  made  of  8-in.  brick  work.  The  top  of  the  chimney  must  pass 
above  the  highest  part  of  the  building.  The  smoke  flue  must 
not  extend  beyond  the  inner  surface  of  the  chimney  flue.  It  is 
well  to  have  a  pocket  at  the  bottom  of  the  chimney  with  a 
clean-out  door  to  remove  soot  when  necessary. 

In  figuring  the  size  of  the  boiler  to  be  used  for  a  steam  or 
hot-water  installation  the  amount  of  heat  required  is  reduced 
to  pounds  of  coal  by  a  method  used  above,  taking  the  efficiency 
at  66  per  cent.  The  rate  of  combustion  may  be  taken  as  5  to  8 
Ibs.  of  coal  per  square  foot  per  hour.  This  gives  the  area  of  the 
grate,  and  from  a  table  the  size  of  boiler  may  be  found. 

Another  way  as  mentioned  above  is  to  compute  the  surface  of 
the  radiation  and  pipes  and  then  select  size  from  a  catalogue. 
These  methods  are  now  applied  to  the  residence  for  a  steam 
boiler  and  after  that  for  a  hot-water  boiler. 

For  the  steam  system  of  the  residence  the  total  amount  of 
radiation  is  624  sq.ft.,  and  the  piping  amounts  to  about  150 
sq.ft.,  giving  a  total  of  774  sq.ft.  This  requires  a  22-in. 
5-section  Ideal  Sectional  Boiler.  Computing  this  from  the  size 
of  the  grate  surface  the  following  results: 

Total  heat  supply  =  188500; 

188500 

Grate  area  =  —     — vy  ,,  vx    =  4  sq.f t 

14000  X. 66X5 

Using  22  ins.  width, 

Length  =  =  26!  ins. 


276          ELEMENTS  OF  HEATING  AND  VENTILATION 

The  grate  surface  of  a  22-5  boiler  is  22"  X  28".  This  method 
gives  the  same  result.  For  the  hot-water  equipment  the  amount 
of  heating  surface  is  1009  sq.ft.  with  150  sq.ft.  of  pipe  surface. 
The  total  surface  is  1159  sq.ft.,  requiring  the  same  size  of 
boiler  as  before. 

The  table  on  page  272  gives  the  leading  dimensions  of  this 
boiler. 

The  flue  of  the  chimney  for  the  boiler  is  now  determined 
from  the  builder's  table  or  else  as  one-eighth  of  the  grate  area. 
The  same  remarks  apply  here  as  to  chimneys  and  flues  of  hot- 
air  furnaces. 

The  flue  in  this  case  is  to  have  an  area  of 

A  =JX4Xi44  =  72  sq.in.    or    d  =  i 


This  is  the  value  given  in  table. 

The  boiler  should  be  set  on  a  foundation  which  forms  the 
bottom  of  the  ash  pit.  This  is  made  of  concrete.  After  the 
boiler  is  connected  and  tested  it  should  be  covered  with  at  least 
two  inches  of  asbestos  or  magnesia  plaster. 

The  furnaces  and  boilers  should  be  provided  with  the  neces- 
_J3ary  gauges,  shovels,  pokers,  cleaners  and  brushes  or  scrapers. 

The  question  of  the  relative  merits  of  the  various  systems 
is  one  which  is  difficult  to  decide,  and  one  about  which  the  various 
manufacturers  are  usually  prejudiced.  As  far  as  efficiency  is  con- 
cerned, if  the  proper  amount  of  heating  surface  is  used,  the  systems 
are  all  equally  good.  If  the  loss  in  the  chimney  gases  amount 
to  35  per  cent,  due  to  the  unburned  gases,  dilution,  hot  gas  or 
any  other  cause,  65  per  cent  of  the  heat  of  the  coal  must 
be  used  in  the  house  somewhere.  From  60  to  65  per  cent  is 
obtained  with  all  furnaces  or  boilers  if  properly  designed,  and 
even  better  results  if  the  fire  is  operated  steadily.  The  great 
trouble  with  most  hot-air  furnace  work  and  the  one  which  is 
the  cause  of  hot  water  and  steam  showing  better  results,  is  the 
fact  that  the  furnace  does  not  contain  sufficient  heating  surface. 
It  is  not  the  fact  that  a  given  furnace  will  heat  a  house  which 
should  count,  but  that  it  will  do  it  without  a  great  loss  of  heat 


FURNACES  AND  BOILERS  277 

to  the  chimney.  The  same  result  would  happen,  although  it 
is  not  so  common,  when  the  boiler  is  much  too  small  for  an 
installation. 

As  far  as  convenience  in  installing  is  concerned  without  the 
use  of  valuable  space  the  hot-air  methods  using  furnace  or  indirect 
radiators  are  better  than  the  direct  systems,  which  take  valuable 
space.  The  indirect  system  is  better  than  the  furnace  system  for 
large  buildings,  as  the  heating  coils  may  be  placed  under  the  stack 
carrying  the  air,  or  air  under  pressure  is  used,  while  the  furnace 
gives  such  a  small  driving  pressure  that  there  is  difficulty  in 
getting  the  proper  flow  on  long  lines. 

The  hot-air  methods  will  supply  air  for  ventilation,  and  this 
air  can  be  brought  in  at  the  proper  humidity.  The  direct-steam 
or  hot-water  system  does  not  permit  of  ventilation,  and  when 
needed  with  this  system,  tempered  air  must  be  brought  in  by 
use  of  a  fan  blower  and  coil. 

The  hot-air  furnace  systems  are  out  of  the  question  for 
large  buildings,  as  the  circulation  is  not  possible.  The  direct 
system  is  suitable  in  that  the  piping  is  easy  to  run  and  does 
not  take  much  space. 

The  indirect  system  of  heating  requires  the  operation  of  a 
steam  engine  or  electric  motor  and  large  air  ducts  and  unless 
ventilation  is  necessary  the  direct  systems  are  easier  and  more 
cheaply  installed.  In  residences  and  office  buildings  where 
there  are  not  many  occupants  in  the  various  rooms,  this  method 
is  quite  extensively  used.  The  method  is  positive  even  to  the 
remotest  parts. 

Steam  systems  are  usually  cheaper  than  hot-water  systems, 
because  less  surface  is  required  owing  to  the  greater  unit  value 
of  the  steam  surface.  The  steam  may  be  raised  more  quickly 
than  the  hot  water,  but  unfortunately  it  drops  more  quickly 
also. 

A  hot-water  system  gives  a  more  uniform  temperature  over 
a  long  period.  It  is  not  subject  to  sudden  changes,  and  the 
radiators  are  at  a  lower  temperature.  It  consumes  time  in  bring- 
ing the  house  to  a  proper  temperature  after  the  house  has  been 
chilled. 


278          ELEMENTS  OF  HEATING  AND  VENTILATION 

The  radiators  in  these  two  systems  take  valuable  space, 
while  if  concealed  they  are  difficult  to  repair. 

As  far  as  cost  of  installation  is  concerned  the  hot-air  fur- 
nace system  is  the  cheapest;  then  follow  direct  steam,  direct 
hot  water,  indirect  steam  and  indirect  hot  water.  The  furnace 
system  for  a  dwelling  house  costs  about  one-half  to  two-thirds 
the  cost  of  a  steam  system. 


CHAPTER  XI 
DISTRICT    HEATING 

District  heating  or  heating  from  a  central  station  has  been 
used  for  a  long  time  in  institutions  where  a  number  of  buildings 
are  within  the  radius  of  several  hundred  feet,  and  this  same 
method  has  been  extended  to  heat  towns  or  portions  of  towns 
when  the  remote  buildings  have  been  several  miles  from  the 
power  house. 

There  are  two  general  methods:  hot  water  and  s:2am.  In 
the  hot-water  system  a  complete  circuit  is  usually  made  with 
a  pump  to  force  the  water  through  the  feed-water  heater  into 
the  supply  main,  from  which  the  water  passes  into  the  buildings 
through  a  service  or  branch  pipe  and  after  passing  through 
the  radiators  it  leaves  through  a  service  and  enters  the  return 
pipe,  passing  back  to  a  discharge  tank  and  thence  to  the  pump. 
The  heater  may  be  an  ordinary  boiler  using  hot  gases  to  heat 
the  water,  or  a  feed-water  heater  using  steam  or  hot  gases  from 
a  boiler  to  heat  the  water.  Any  form  of  heater  may  be  used. 

In  the  steam  system,  live  steam  from  boilers  or  exhaust 
from  engines  passes  through  the  supply  main  and  service  pipes 
to  the  buildings  and  in  some  cases  the  returns  from  the  buildings 
are  carried  back  to  the  power  house,  while  in  other  cases  this 
water  of  condensation  is  sent  to  the  sewer. 

In  the  hot- water  system  there  is  no  reason  why  the  pipe  should 
be  laid  on  a  definite  grade.  It  may  follow  the  contour  of  the 
surface  of  the  ground  through  which  it  passes.  In  this  system 
when  closed  there  is  no  power  consumed  in  raising  water  to  the 
tops  of  tall  buildings,  as  the  down  legs  will  balance  the  weight 
of  the  up  legs.  In  fact  there  is  really  some  motive  power  due 
to  the  greater  weight  of  cold  water  in  the  down  legs.  The  water 
may  be  measured  by  meter  and  if  the  temperatures  of  inlet  and 

279 


280         ELEMENTS  OF  HEATING  AND  VENTILATION 

outlet  are  known  the  heat  used  by  a  building  is  determined. 
This  latter  factor  is  the  difficult  one  to  find  at  the  con- 
sumer's building  in  a  hot-water  district  system  during  the  whole 
season. 

The  hot  water  may  be  stored  in  times  of  peak  load  if  the 
system  uses-  exhaust  steam  to  heat  the  water  and  this  water 
may  be  used  in  time  of  small  steam  load  on  the  engines. 

In  the  steam  system,  the  steam  and  return  mains  must  be 
put  on  a  definite  grade  if  the  mains  are  to  be  dripped  and  all 
drips  and  condensation  are  to  be  returned  to  the  power  house. 
This  grade  may  mean  considerable  cutting  to  accommodate 
the  contour  of  the  ground  surface,  or  if  this  is  not  done  all  low 
spots  must  be  drained  and  a  pump  used  to  return  the  drips  and 
condensation.  These  two  reasons  have  resulted,  in  many  cases, 
of  employing  a  single  pipe  in  steam  systems  allowing  all  drips 
and  condensations  to  pass  into  the  sewer.  To  cut  down  the  loss 
of  heat  in  such  cases,  the  drips  from  the  low  points  of  the  line 
are  taken  into  a  customer's  property  and  passed  through  a  tem- 
pering coil  so  as  to  heat  some  of  the  ventilating  air  of  the  building. 
The  same  method  is  used  with  the  condensation  of  the  building 
and  thus  the  water  is  discharged  into  the  sewer  at  a  very  low 
temperature.  In  this  system  much  of  the  exhaust  steam  at 
peak  load  must  be  wasted  unless  live  steam  is  largely  used  for 
the  heating  plant  at  small  loads  and  thus  the  advantages  of  the 
use  of  the  heating  plant  as  a  by-product  plant  are  not  attained. 
In  many  cases  where  boilers  are  used  for  heating,  the  exhaust  of 
engines  at  certain  times  is  used  to  do  part  of  it,  as  in  an  office 
building,  but  in  a  true  district-heating  system  there  is  generally 
a  waste  of  steam  at  peak  engine  load  when  exhaust  steam  is 
used. 

The  steam  system  in  most. cases  dispenses  with  the  use  of 
the  distributing  pump,  as  5  or  6  Ibs.  back  pressure  will  carry  the 
steam  a  considerable  distance. 

The  pipes  in  a  district  system  are  installed  so  as  to  properly 
drain,  so  that  expansion  is  cared  for  and  so  that  the  heat  losses 
may  be  reduced  to  a  minimum. 

To  properly  drain  the  pipes  a  uniform  grade  must  be  estab- 


DISTRICT  HEATING 


281 


lished,  or  high  and  low  points  are 
suited  to  these.     The 
low  points  are  usually 
placed    at    manholes 
so  that  traps  may  be 
placed  there  which  are    — — — — 
accessible  for  adjust- 
ment   or    repair    for 
steam  systems   or   so  that   drains 
may  lead  to   the   sewer  in   water 
systems.      Drainage  is  important, 
as  corrosion   and    rusting    are  the 
main  troubles  in  district  systems. 
It  is  claimed  by  advocates  of  the 
steam  system  that   the  pipes  will 
not  corrode  as  rapidly  with  steam 
as  they  will  when  hot  water  is  used. 
The  rusting   out    of   pipes   is  one 
important  objection  to  this  system. 

The  expansion  is  cared  for  by 
swinging  ells,  by  slip  expansion 
joints,  by  pipe  bends,  by  corrugated 
pipes  or  by  a  special  contrivance 
known  as  a  variator.  These  are 
shown  in  Fig.  196.  They  are  all 
of  value.  The  slip  expansion  joint 
is  objectionable  in  that  the  leakage 
from  the  packing  is  hard  to  care 
for  and  at  times  the  sleeve  becomes 
incrusted  so  that  it  does  not  slip 
easily.  The  swinging  ells,  although 
efficient  in  caring  for  expansion, 
have  a  large  amount  of  resistance, 
and  this  is  objectionable. 

The  corrugated  pipe  section  is 
one  which  offers  little  resistance 
and  allows  the  expansion  to  take 


fixed  and  the  pipe  grade  is 


FIG.  196. — Arrangements  for 
Expansion. 


282 


ELEMENTS  OF  HEATING  AND  VENTILATION 


place  easily.  The  same  may  be  said  of  the  pipe  bend,  on 
account  of  the  large  radius  of  the  bend. 

The  variator  has  a  flexible  diaphragm  to  make  the  move- 
able  joint  steam  tight.  When  used  it  is  provided  with  outlets 
at  top  and  bottom  so  that  service  pipes  and  drip  pipes  can  be 
run  from  this  point  as  the  main  casting  is  anchored  and  does 
not  move.  The  variator  shown  is  a  single  one  in  which  the  expan- 
sion occurs  in  one  side.  Double 
variators  permit  the  pipes  on 
each  side  to  move  relative  to  the 
casing. 

To  care  for  the  radiation  loss 
several  methods  are  used.  In 
some  cases  pipes  are  covered 
with  pipe  covering,  while  in 
other  cases  the  pipe  is  buried 
in  a  wooden  box  and  surrounded 
by  shavings,  or  the  pipe  may  be 
placed  in  a  wooden  pipe  made 
up  of  thick  staves  joined  to- 
gether. 

The  pipe  covering  is  used 
when  the  pipe  is  carried  in  tun- 
nels, Fig.  197,  or  in  certain  forms 
of  conduits,  Fig.  198.  Tunnels 
are  so  expensive  to  construct 
that  they  are  rarely  used  except 
between  buildings  of  a  manufac- 
turing plant  where  steam  mains 

are  carried  from  a  central  plant  to  a  group  of  buildings,  or 
in  a  district  system  where  a  number  of  branch  mains  are  carried 
from  the  power  house  to  a  point  from  which  the  lines  radiate. 
The  tunnel  should  be  made  sufficiently  large  for  men  to  walk 
through  and  to  care  for  the  pipe  lines.  The  clear  passageway 
outside  of  the  standards  should  be  at  least  24  ins.  wide  and  5^ 
or  6  ft.  high.  The  crowded  or  small  tunnel  may  be  right  for 
the  original  installation  when  the  pipes  and  tunnel  are  coldr 


FIG.  197. — Tunnel. 


DISTRICT  HEATING  283 

although  even  then  work  is  difficult,  but  when  a  broken  or  leaky 
main  needs  repairing,  work  is  almost  impossible  on  account  of 
the  heat.  Brick  arches  are  used  for  the  roofs  of  tunnels,  beams 
may  be  used  with  flat  brick  arches  or  reinforced  concrete  may  be 
employed.  The  walls  should  be  12  ins.  thick.  The  floor  of 
all  tunnels  should  drain  to  one  side  and  the  gutter  should  drain 
to  proper  sumps  or  sewers  so  that  no  water  will  remain  on  the 
floor.  Water  is  not  only  hard  on  workmen,  but  the  dampness 
is  likely  to  cause  the  covering  to  mildew  and  rot. 

The  pipe  supports  are  made  by  fastening  if-  or  2  -in.  pipes 
into  the  floor  and  roof  and  then  using  a  pair  of  strap  irons 
clamped  into  position  by  bolts.     In 
this  way  any  alignment  may  be  had 
with  ease. 

The  arrangement  of  underground 
conduits  as  shown  in  Fig.  198  with 
pipe  covering  around  the  pipe  gives 
a  very  satisfactory  construction.  Split 
tile  or  gutter  tile  are  made  of  regular 
terra  cotta  and  are  manufactured 
with  a  cut  from  the  inside  surface  FIG.  198.— Split-tile  Conduit, 
almost  to  the  outside,  so  that  on 

striking  them  they  break  into  two  parts.  One-half  is  then  placed 
in  the  trench  and  well  rammed  into  position  for  alignment  and 
level,  with  the  joints  between  the  lengths  of  tile  made  up  with 
mortar  of  one  part  cement  and  three  parts  sharp  sand.  The  pipe 
is  supported  at  10-  or  i2-ft.  intervals  in  one  of  several  ways.  A 
simple  method  of  support  is  to  place  a  piece  of  pipe  across  the  tile 
in  grooves  after  cutting  them  in  the  side  of  the  tile  so  that  the 
steam  pipes  are  at  the  proper  level  in  the  conduit.  After  the  cover 
is  put  on  at  this  section  concrete  of  one  part  cement,  three  parts 
sharp  sand  and  six  parts  broken  stone  of  2  ins.  size  is  placed 
around  this  section,  filling  a  hole  about  15  ins.  long  in  the  direction 
of  the  pipe  and  extending  out  about  10  or  12  ins.  and  reaching 
the  full  height  of  the  tile.  This  is  shown  in  Fig.  199.  Another 
method  is  to  use  concrete  sections  at  the  proper  distance 
apart  in  which  rollers  or  rods  as  shown  in  Fig.  199,  are  used 


284 


ELEMENTS  OF  HEATING  AND  VENTILATION 


to  carry  the  pipe.  For  conduit  work,  the  pipe  should  have 
screw  connections,  as  flange  connections  leak.  After  the  pipe 
is  installed  it  should  be  tested  with  water  pressure  to  a 
pressure  a  little  above  that  to  be  carried,  and  if  found  tight,  the 
covering  is  placed  around  the  pipe,  the  top  half  of  the  split  tile 
put  on  and  joints  cemented.  Then  the  ditch  is  back  rilled,  care 
being  taken  to  ram  or  tamp  the  earth.  At  times  the  earth  is 
puddled  with  water  during  rilling  to  make  the  earth  pack  properly. 
This  tile  is  usually  water-tight  if  all  joints  at  sides  and  ends 
are  properly  cemented  together,  but  at  times  it  is  well  to  drain 
the  conduit  by  placing  crushed  stone  beneath  it  and  placing  an 
unglazed  tile  at  the  center  of  the  stone  to  give  a  waterway  for 


FIG.  199. — Supports  for  Pipes  in  Conduits. 

the  seepage.  This  tile  of  course  leads  to  a  sump  or  sewer.  This 
is  necessary  in  some  cases  to  keep  the  water  from  working  into 
the  conduit.  Of  course  as  shown  in  the  figure  any  water  reaching 
the  conduit  would  flow  along  the  bottom  to  the  manhole.  Figs. 
197,  198  illustrate  installations  where  the  return  is  brought  back 
to  the  power-house,  while  Figs.  20x3-203  show  systems  when 
there  is  no  return. 

Manholes  should  be  placed  at  intervals,  especially  at  branches, 
and  by  making  the  floor  at  a  lower  level,  the  seepage  water 
collects  here  and  may  be  removed.  Fig.  200  shows  the  sections 
of  manholes.  The  tops  of  these  should  be  made  as  tight  as 
possible  with  a  double  cover  to  cut  down  radiation  losses. 

At  times  the  insulating  material,  consisting  of  loose  asbestos 
or  magnesia,  is  filled  into  the  conduit  around  the  pipe,  and  in  that 


DISTRICT  HEATING 


285 


case  no  water  should  be  allowed  to  enter.  Figs.  201,  202  and  203 
show  various  methods  of  carrying  single  pipes.  In  Fig.  201  a 
wooden  box  is  made  up  with  air  spaces.  These  spaces  are  filled 
with  some  substance  to  break  up  the  air  currents.  The  pipe  is  sur- 
rounded by  some  filler  to  stop  air  circulation  and  the  whole  box  is 
covered  with  pitch.  In  Fig.  202  the  box  is  made  of  concrete  and 


FIG.  200. — American  District  System. 

in  Fig.  203  the  pipe  is  surrounded  by  a  wooden  covering  and  the 
whole  is  surrounded  by  concrete.  In  the  last  three  methods  the 
pipe  is  carried  by  some  form  of  roller.  Fig.  200  shows  the  method 
used  by  the  American  District  Steam  Co.  The  pipe  or  casing, 
Fig.  204,  is  made  of  wood  staves  4  ins.  thick  locked  together 
by  tongues,  wrapped  with  wire  and  lined  with  tin.  The  pipe  has 
an  air  space  of  i  in.  between  the  tin  and  the  sheet  asbestos  which 
is  placed  around  the  pipe.  The  staves  are  treated  with  creosote 


286 


ELEMENTS  OF  HEATING  AND  VENTILATION 


after  shaping  and  after  banding  with  a  spiral  of  A  in.  galvanized 
wire  embedded  into  the  wood.  A  3^-in.  bell  and  spigot  is  formed 
at  the  end  by  turning  after  the  pipe  is  made.  The  exterior 
is  then  treated  with  asphaltum,  pitch  and  sawdust. 


FIG.  201. — Wooden  Conduit. 


The  American  District  Steam  Co.  install  their  apparatus 
as  shown  in  Fig.  200,  using  manholes  at  all  special  fittings  such 
as  variators  (see  Fig.  196)  or  at  anchor  specials.  These  anchor 


FIG.  202. — Concrete  Conduit. 

specials  are  usually  tees  or  crosses  which  supply  the  service  con- 
nections. The  variators  also  are  points  for  connecting  service 
mains  or  drips,  as  the  main  body  is  always  so  anchored  that  it 


DISTRICT  HEATING 


287 


is  a  fixed  point.  The  variators  care  for  50  ft.  of  pipe  so  that 
double  variators  are  100  ft.  apart  with  an  anchor  special  between 
them.  In  this  way  outlets  may  be  made  at  5o-ft.  intervals. 
The  third  manhole  is  used  to  control  certain  sections  of  the  pipe. 


FIG.  203. — Wooden  Conduit  in  Concrete. 

In  laying  out  a  district  system  the  map  of  the  buildings 
to  be  supplied  by  a  plant  should  be  laid  out  and  then  the  profile 
of  the  line  made,  giving  the  cuts  at  the  various  points.  In  many 
cases  these  lines  may  be  placed  in  alleys  or  small  streets  parallel 
to  the  main  streets,  in  which  the  pavement  is  not  so  expensive 


FIG.  204. — Wooden  Covering. 

and  which  will  not  interfere  with  traffic  during  construction  or 
repairs. 

The  steam  or  water  used  by  the  various  buildings  is  then 
found  and  allowance  is  made  for  future  growth  and  extension, 
and  then  the  pressure  to  be  expected  at  the  various  points 


288         ELEMENTS  OF  HEATING  AND  VENTILATION 

is  assumed.  By  starting  at  the  dead  ends  of  the  mains  and  work- 
ing toward  the  source,  the  amount  of  steam  or  water  and  the 
pressure  drop  on  any  line  are  known.  From  this  the  size  of  the 
pipe  may  be  found  for  the  assumed  pressures. 

There  is  a  heat  loss  from  the  pipe  line  due  to  radiation,  but 
in  pipes  lying  buried  in  conduits  surrounded  by  earth  this  quan- 
tity is  much  smaller  than  in  pipes  carried  in  a  room.  Experiment 
seems  to  indicate  a  formula  for  the  heat  per  hour  in  the  form 


H  = 


.  of  external  pipe  surface. 


(160) 


g 

fc       0.15  Ib. 
g  150  B.T.U. 

| 

£       0.10  Ib. 
tf  100  B.T.U. 

OS 

1 

*       0.05  Ib. 
°.    50  B.T.U. 

3 

/ 

. 

/ 

/ 

/ 

/ 

/ 

/ 

• 

- 

^ 

^ 

• 

^—  — 

100°                    150°                    200°                    250°                    300°                    351 
Temp.of  -Fluid  in  J?ipe 

FIG.  205. — Curve  for  Values  of  R. 

R  depends  on  the  steam  temperature  and  is  given  by  the  curve 
shown  in  Fig.  205.  This  curve  has  been  constructed  from 
various  experimental  results.  It  is  given  in  pounds  of  steam 
condensed  per  square  foot  per  hour  or  in  B.t.u.  per  hour. 
The  value  of  0.03  Ibs.  per  hr.  is  used  for  water  and  0.05  for  5 
Ibs.  steam.  The  constant  R  may  vary  considerably,  increasing 
as  the  covering  becomes  old  or  water-soaked. 


DISTRICT  HEATING  289 

Some  authors  consider  a  loss  due  to  friction,  but  this  is  not 
a  loss,  as  the  heat  produced  by  this  friction  remains  in  the  steam 
and  although  the  pressure  may  drop  there  is  no  diminution 
of  heat  outside  of  radiation. 

This  method  of  assuming  pressures  will  not  give  the  best 
size  necessarily,  unless  the  assumed  pressure  drop  from  the  plant 
to  the  end  of  the  line  is  the  maximum  possible  amount.  In 
that  case  the  pipe  is  the  best  size,  but  when  the  pressure  can  be 
changed  a  smaller  pipe  with  more  drop  might  be  more  economical. 
This  problem  of  economical  size  of  pipe  divides  itself  into  two 
problems,  one  for  water  and  one  for  steam. 

In  the  case  of  the  hot-water  system  it  is  well  to  determine 
the  cost  of  installing  a  certain  size  of  main  and  then  the  cost 
of  pumping  the  water  through  the  main  and  the  heat  loss  from 
it.  After  this  is  done  a  larger  pipe  is  taken  and  in  this  the  cost 
of  pumping  will  be  less,  due  to  the  lower  velocity,  but  the  instal- 
lation will  cost  more  and  there  will  be  a  greater  radiation 
loss.  If  the  sum  of  the  cost  of  pumping,  of  radiation  and  of 
interest,  depreciation  and  taxes  be  less  for  the  large  pipe  than 
for  the  smaller  one,  the  large  pipe  should  be  used.  If,  however, 
the  interest,  taxes  and  insurance,  radiation  and  pumping  cost 
more  than  the  sum  of  these  quantities  for  the  small  pipe,  the 
latter  should  be  used  in  preference  to  the  larger  pipe,  and  more- 
over it  would  pay  to  investigate  a  still  smaller  pipe.  In  this 
way  one  size  is  found  which  gives  the  most  economical  result. 
As  an  example  suppose  100,000  Ibs.  of  water  is  to  be  carried 
per  hour  to  a  building  3000  ft.  from  the  power  house  at  170° 
and  returned  at  140°  F.  The  size  of  the  main  is  required. 

i  st.  Suppose  the  pressure  fall  is  fixed  at  10  Ibs.  per  square 
inch^and  this  can  and  should  be  used.  This  permits  of  one 
answer  only,  and  assuming  a  4-lb.  drop  in  the  building,  6  Ibs.  may 

be  used;  6  Ibs.  per  square  inch  is  equivalent  to  -r—  -—  =  14.1 

OI.Oo 

ft.  of  water  at  155°  F.  (at  the  mean  temperature). 

100000 

=°'45  CU'ft  Per  Sec' 


6oX6oX6i.o8 


290         ELEMENTS   OF  HEATING  AND  VENTILATION 

The  formula  to  be  used  to  determine  the  quantity  depends 
on  that  used  to  determine  the  friction  head.  The  formulae 
mentioned  in  Chapter  VII  are  not  considered,  as  the  loss  in 
district  systems  is  so  great  that  more  accurate  methods  must 
be  employed.  The  approximate  formula  of  Chapter  VII  was 
sufficient,  as  the  runs  were  short  in  that  work.  The  formula 
from  the  work  of  Williams  and  Haven  as  given  by  I.  N.  Evans  is 

pl-85 

A  =  0.00035*  -p^     ......     (161) 

while  the  formula 


which  has  been  used  for  so  many  years,  has  a  constant  term  f 
which  depends  on  the  v  and  d.  The  tabular  values  of  /  which 
have  been  used  indicate  approximately 


Using  this  the  formula  becomes 

01*876 

/*=  0.0004/^25"  ............     (164) 


2,1-875  Ql-875  Ql-875 

-^  =  0.0004   /\  1-875^5  = 

W 


For  the  problem 

.0006X6000X0.451'875  \ 


DISTRICT  HEATING  291 

2d.  Suppose  the  pressure  is  not  limited  and  it  is  desired  to 
know  whether  a  6-in.  or  8-in.  pipe  would  be  better  than  a  7  in., 
supposing  i  H.P.  hr.  is  worth  i  J  cts.  to  this  company. 

O.A.Z 

Velocity  in  6-in.  line  =  -  —  =  2.2  ft.  per  second; 
Velocity  in  7-in.  line  =      ,    =i-7  ft.  per  second; 

Velocity  in  8-in.  line  =  -    —  =  1.3  ft.  per  second; 
°-3474 

Loss  in  6-in.  line  =  -  -  i^y^~  X2.21<875  =  25.2  ft.; 

0.0004X6000 
Loss  in  7-in.  lme  =     0>583i.25      Xi.71>875  =  i2.7  ft; 


Loss  in  8-in.  1^  = 

Friction  horse-power: 

,  .     r       25.2X61.08X45 
6-m.  line,  —  --  —  =  1.26; 
550 

12.7X61.08X45 
7-in.  line,  -  -  =0.61  ; 

0  .      r        6.5X61.08X045 

8-in.  line,  —  -  -  ^^=0.32. 

Oo 

Total  horse-power  to  drive  pump,  assuming  a  50  per  cent 
overall  efficiency,  is  as  follows: 

6-in.  line,  2.52; 
7-in.  line,  1.22; 
8-in.  line,  0.64. 


292          ELEMENTS  OF  HEATING  AND  VENTILATION 

Cost  of  power,  using  200  heating  days  at  an  average  of  1  5  hrs, 
at  full  capacity  : 

6-in.  line  =  2.52X200X15X4  =$113.  50; 
7-in.  line  =1.22X45.00  =     54.90; 

8-in.  line  =  .64X45.  oo  =     33.80. 

Radiation  loss: 

6  ins.,  0.03X1.734X6000  =  312  Ibs.  of  steam; 

7  ins.,  0.03X1.996x6000  =  359  Ibs.  of  steam; 

8  ins.,  0.03X2.255X6000  =  406  Ibs.  of  steam. 

With  heat  worth  35  cts.  per  1,000  Ibs.  of  steam  the  cost  of  the 
radiation  is 


7  ins.,359Xi^Xl5Xo.35=  376.50;         ' 

406X200X15 

8  ms.,  -  --  Xo.35  =  426.00. 

The  cost  of  excavation  and  back  filling  for  the  pipe  will  cost  20 
to  30  cts.  a  cubic  yard,  but  this  item  will  not  vary  much,  if  at 
all,  for  the  different  sizes  of  pipes. 

The  list  prices  per  foot  of  the  pipes  and  covering   are  as 
follows: 

For  Pipe  For  Wood  Casing 

6  ins.,  $1.88  $1.94 

7  ins.,    2.35  2.16 

8  ins.,    2.82  2.44 

Assume  discount  as  70-10-10  on  pipe,  50-20  on  casing. 

Cost  of  casing: 

6  ins.  =  $1.94  X  6000X40  =  $4660.00; 
7ins.=  2.16X6000X40=  5180.00; 
Sins.  =  244X6000X40=  5860.00; 


DISTEICT  HEATING  293 

Cost  of  pipe: 

6ins.=  1.88X6000X0.243=12740.00; 
yins.=  2.35X6000X0.243=  3420.00; 
8ins.=  2.82X6000X0.243=  4115.00. 

If  interest  amounts  to  5  per  cent,  taxes  to  if  per  cent,  and 
depreciation  to  4.6  per  cent  (if  the  life  is  taken  at  fifteen  years), 
the  yearly  cost  of  the  investment  will  be: 

6  ins.  =  7400.00X11.1  =  $821.40; 

7  ins.  =8600.00X11.1  =     954.60; 

8  ins.  =9975.00X11.1  =   1107.22. 

The  cost  of  installation  will  be  taken  to  be  the  same  for  each 
line,  as  will  practically  be  the  case,  or  it  might  be  considered 
to  be  included  as  a  per  cent  of  the  cost  of  the  pipe  and  casing 
and  figured  in  as  part  of  investment  just  computed.  Yearly 
cost  then  becomes: 


For  6  ins. 

For  7  ins. 

For  8  ins. 

Interest 

$821.40 

$954.60 

$1107.  22 

Radiation 

327-50 

376.50 

426.OO 

Power 

II3-50 

54-90 

33-80 

Total  cost    $1272.40          $1386.00          $1567.02 

This  shows  that  the  smalles.  pipe  is  best.  The  yearly  cost 
should  now  be  worked  out  for  a  5~in.  pipe  and  the  result  would 
show  a  slight  decrease  in  the  cost  ($1242.61).  The  use  of  a 
4-in.  pipe  would  increase  the  cost  of  power  so  much  that  the 
total  cost  would  be  increased.  The  difference  between  the  yearly 
cost  of  the  5  and  6  in.  is  so  slight  that  it  would  be  well  to  use  the 
6  in.,  since  if  more  water  were  needed  this  would  care  for  it  with 
less  cost  of  power  and  the  other  items  would  be  the  same.  For 
that  reason  it  would  be  cheaper  to  operate  than  the  5  in.  except 
under  the  conditions  of  the  problem. 

For  steam  pipe  there  is  not  much  power  consumed,  and  if 
the  pressure  can  be  taken  to  a  high  point  it  may  pay  to  use  high- 
pressure  steam,  since  this  steam  is  more  dense.  The  main 


294         ELEMENTS  OF  HEATING  AND  VENTILATION 

consideration  in  steam-pipe  work  is  whether  or  not  the  small 
pipe  with  a  higher  temperature  difference  will  radiate  so  much 
heat  that  its  cost  added  to  the  yearly  cost  on  the  investment 
will  be  more  or  less  than  on  a  larger  pipe  with  low-pressure  steam, 
in  which  the  cost  of  installation  is  greater,  but  the  heat  loss  is 
less.  If  the  computation  is  made  it  will  be  found  that  the 
yearly  cost  is  less  on  the  small  pipe  carrying  high-pressure  steam. 
If  possible  live  steam  should  be  used  in  the  transmission  main. 
When  exhaust  steam  is  to  be  used,  large  pipes  have  to  be 
employed  to  accommodate  the  low-density  steam.  The  method 
of  calculation  is  similar  to  that  used  before.  The  items  con- 
sidered are  the  cost  per  year  for  investment  and  loss  of  heat 
at  different  pressures,  using  the  various  sizes  of  pipes  resulting 
from  the  use  of  the  formula  for  size  in  terms  of  the  drop,  steam 
pressure  and  length  (see  p.  139).  These  systems  are  applied 
as  shown  in  Figs.  206,  207,  the  first  being  for  a  town  while  the 
second  is  for  an  institution.  Each  of  these  is  used  in  the  same 
manner  by  assuming  pressure  drops  and  quantities  from  which 
the  diameters  are  found,  and  then  an  economic  study  is  made 
with  a  change  in  certain  of  the  conditions,  the  idea  being  to 
make  the  operating  cost  and  fixed  charges  as  small  as  possible. 

The  costs  are  usually _figured  per  1000  Ibs.  of  steam,  per 
1,000,000  B.t.u.  or  per  square  foot  of  radiation.  The  charges 
are  about  60  cts.  per  1000  Ibs.  of  steam  and  35  cts.  per  square 
foot  of  steam  radiation  per  season  and  20  cts.  per  square  foot 
of  hot-water  radiation. 

Gifford  states  that  the  annual  charge  for  heat  should  be 
divided  monthly  in  the  following  proportion: 

October 3  per  cent 

November 12 

December 18        " 

January 21 

February 19 

March 13 

April 8        " 

May 3        " 


DISTRICT  HEATING 


FIG.  206.— District  Heating  of  a  City.     (From  Catalogue  of  American  District 

Heating  Co.) 


296          ELEMENTS  OF  HEATING  AND  VENTILATION 


The  following  might  also  be  used  in  northern  climates,  where 
March  is  a  hard  month: 

October 5  per  cent 

November 10  " 

December 15  ' ' 

January 20  " 

February 20  ' ' 

March 15 

April 10 

May 5  " 

100  per  cent 


HEATING  MAINS 

RENSSELAER  POLYTECHNIC 

INSTITUTE 


FIG.  207. — District  Heating  of  an  Institution. 

The  value  of  district  systems  is  due  to  the  fact  that  a  uniform 
heat  is  always  available  and  there  is  no  dirt  or  expense  for  main- 
taining or  caring  for  the  furnace,  ashes  and  coal.  The  expense 
may  be  higher  than  the  cost  of  coal,  but  should  not  exceed  the 
cost  plus  the  cost  of  operating  the  furnace.  The  absence  of 
dust  from  coal  and  ashes  has  undoubtedly  a  money  value  which, 
although  it  is  not  possible  to  fix,  nevertheless  should  be  con- 
sidered in  estimating  the  value  of  this  method  of  heating. 

This  system  also  gives  a  cleaner  town  in  that  the  numerous 
smoking  chimneys  are  taken  away  from  the  location  of  the 
high-grade  property. 


DISTRICT   HEATING 


297 


In  maintaining  mains  care  must  be  taken  to  stop  all  leaks 
at  any  place,  for  very  small  openings  are  great  sources  of  loss. 
A  J-in.  hole,  for  instance,  at  5  Ibs.  steam  pressure,  would  dis- 
charge about  36,000  Ibs.  of  steam  per  month,  using  over  two 
tons  of  coal. 

The  pipe  should  be  full- weight  pipe  (specially  selected  to  see 
that  all  is  uniform  and  of  proper  weight),  and  the  fittings  should 
be  extra  heavy.  All  breaks  are  guarded  against,  as  it  is  very 
expensive  to  repair  pipes  installed  in  the  usual  manner.  In 
designing  tunnels  it  is  well  to  place  a  number  of  inclined 
openings  leading  to  the  ground  level  at  intervals  for  the  intro- 
duction of  new  pipes  when  necessary. 


FIG.  208.— Oscillating  Water  Meter. 

When  pipes  and  conduits  are  placed  in  streets  the  back  fill 
must  be  well  rammed  and  puddled  to  avoid  subsequent  settling, 
and  on  top  of  this  fill  a  good  concrete  base  should  be  put  over 
the  hole  to  support  the  pavement. 

The  meters  used  for  steam  condensation  should  be  of  the 
oscillating  bucket  type,  Fig.  208,  so  that  no  water  will  leak  at 
times  of  small  discharge.  The  trouble  with  many  meters  is  the 
fact  that  they  allow  a  small  rate  of  flow  to  remain  unrecorded 
and  for  that  reason  the  type  above  is  of  value.  To  regulate  the 
flow  of  water  into  buildings  in  the  hot-water  system  it  has 
been  suggested  to  insert  standard  orifices  in  the  service  con- 


298         ELEMENTS   OF  HEATING  AND   VENTILATION 

nections.  These  are  made  smaller  near  the  station,  where  the 
difference  of  pressure  between  main  and  return  is  greater  than 
at  the  end.  These  smaller  orifices  prevent  a  large  quantity 
from  passing  into  the  services  near  the  station,  which  would 
mean  a  higher  temperature  on  the  return  than  should  exist  at 
this  building.  It  would  indicate  that  the  water  was  not  doing 
its  proper  work,  as  its  return  temperature  was  too  high.  By 
observing  the  return  temperature  from  a  building  the  correct- 
ness of  the  orifice  may  be  known.  If  low,  the  orifice  is  too  small; 
if  high,  the  orifice  is  too  large. 

There  should  be  constant  inspection  of  all  manholes  for  the 
evidences  of  leakage  from  expansion  joints,  valves,  conductors, 
and  to  see  if  traps  are  clean.  These  should  be  blown  out  and 
cleaned  at  regular  intervals. 

One  form  of  district  heating  is  that  used  for  car  heating 
on  railroad  systems.  The  heat  is  supplied  from  the  locomotive. 
A  i -in.  extra-heavy  pipe  is  taken  from  the  dome  through  a  stop 
valve  and  a  pressure  regulator,  the  outlet  of  which  is  i  J  and  after 
passing  the  T  for  the  gauge,  the  line  enlarges  to  i|  ins.  It  is 
connected  to  i|-in.  covered  pipes  under  the  tender  and  cars 
by  means  of  special  steam  hose  couplers.  Each  coupler  is  pro- 
vided with  a  trap  which  opens  to  drain  the  line  as  soon  as 
steam  is  cut  from  it. 

The  pressure  regulator  is  a  spring-controlled  reducing  pres- 
sure valve  of  such  a  construction  that  it  will  operate  properly 
on  the  moving  locomotive. 

The  ij-in.  train  pipe  has  a  ij-in.  branch  under  the  center 
of  each  car  and  this  is  split  into  two  i-in.  branches,  each  one 
running  to  a  i-in.  angle  valve  under  a  seat  near  the  center  of 
each  side.  The  line  on  each  side  enlarges  to  2  ins.  and  a  loop 
is  taken  along  the  side  of  the  car,  care  being  exercised  to  use  a 
right-angle  section  at  one  end  to  care  for  expansion,  as  was  done 
in  the  corner  coil  of  Fig.  63.  The  condensation  in  this  line 
is  then  carried  through  a  trap  and  discharged  from  the  system 
beneath  the  car.  This  trap  is  made  on  the  same  principle  as 
was  used  in  the  thermograde  motor  valve,  Fig.  79.  As  soon 
as  steam  strikes  it  the  valve  closes.  There  is  usually  a  trap- 


DISTRICT  HEATING  299 

which  opens  as  soon  as  the  pressure  is  cut  off,  to  ensure  that  all 
water  is  drawn  off,  thus  preventing  freezing. 

Each  car  is  equipped  with  a  train  pipe  valve  at  the  center 
of  the  car  or  at  the  end.  These  valves  are  used  to  close  off  the 
train  line  at  the  last  car.  They  are  provided  with  traps  to 
relieve  the  line  of  water. 

The  direct  steam-heating  system  is  valuable  in  that  it  is 
rapid,  effective,  and  when  cut  out  there  is  no  danger  of  freezing. 
The  objection  is  that  there  is  no  storage  and  as  soon  as  steam 
is  cut  off  the  car  begins  to  cool.  For  storage  and  for  a  less 
intense  heat  hot  water  is  used.  This  is  heated  in  a  coil  placed 
in  a  fire  pot  of  a  heater,  or  steam  from  a  train  line  is  introduced 
into  a  small  pipe  within  the  coil  and  heats  the  water.  This 
avoids  the  cracking  noises  which  occur  with  steam  lines  at  times. 
By  using  brine  the  liquid  is  prevented  from  freezing.  At  times 
for  storage  terra  cotta  bricks  are  surrounded  by  a  large  pipe 
and  these  are  heated  by  the  steam.  The  tile  retains  the  heat 
for  some  time. 


CHAPTER  XII 


TEMPERATURE  CONTROL  AND  DRYING  BY  AIR 

THE  control  of  temperature  is  more  or  less  important  for  the 
comfort  of  those  occupying  the  rooms  and  for  the  economical 
operation  of  a  plant.  The  great  trouble  with  various  systems 
for  this  purpose  is  the  disarrangement  of  parts  due  to  the 
delicacy  of  the  apparatus  and  to  the  maltreatment  which  they 
receive  from  tnose  who  do  not  understand  the  adjustment  of 
them.  When  they  cease  to  operate  properly  the  radiator  valves 

cannot  be  opened  or  closed 
and  hence  the  occupants  of  a 
room  may  be  driven  out  by 
the  cold  or  heat  without 
power  to  correct  the  evil. 

There  are  several  simple 
as  well  as  some  complicated 
systems  applied  to  all  methods 
of  heating. 

The  Johnson  system  of 
temperature  control  consists 
of  a  thermostat  which  con- 
trols the  admission  of  air  from 
a  compressed-air  supply  into 
a  case  above  a  diaphragm  at 
the  top  of  the  valve,  Fig. 
209.  This  admission  of  air 
closes  the  valve.  The  air  is 
compressed  by  electric  motors  or  small  water  motors, 

At  a  given  pressure  of  14  or  15  Ibs.  in  the  storage  tank  the 
motors  are  shut  off.     The  air  is  then  carried  to  the  thermostats 

300 


FIG.  209. — Section  of  Diaphragm  Valve. 


TEMPERATURE  CONTROL  AND   DRYING  BY  AIR       301 


in  small  pipes  and  from  these  it  is  conducted  through  other 
small  pipes  to  the  valves.  The  pipes  are  small  in  diameter  and 
are  usually  concealed  in  the  plaster.  The  air  used  is  screened 
when  entering  the  apparatus  to  pre- 
vent foreign  particles  entering  the 
system. 

The  thermostat  is  really  a  valve 
controlling  the  admission  of  air  under 
pressure  into  the  pipe  leading  to  the 
radiator  valve,  or  permitting  the  air 
to  escape  the  valve  line.  The  ther- 
mostat, Fig.  2io,is  carried  on  the  plate 
A,  which  is  attached  to  the  wall  and 
the  brass  block  B,  which  forms  the 
end  of  the  supply  pipe  C  and  the  valve 
pipe  or  motor  pipe  D.  The  upper  of 
the  two  pin  valves  EE  is  used  to  shut 
off  the  air  if  the  thermostat  is  taken 
off,  while  the  lower  one  regulates  the 
flow  to  the  valve  motor.  From  the 
upper  valve  E  the  air  is  led  by  a 
crooked  passage  to  the  air  valve  F. 
This  valve  is  closed  in  the  figure  and 
if  there  is  any  excess  air  in  D  it,  can 
escape  around  the  spindle  G.  When 
the  spindle  is  moved  out  the  disc  F 
opens  the  pipe  C  but  closes  the  an- 
nular space  around  G  so  that  the  air 
cannot  escape,  and  hence  it  passes 
into  D. 

The  rubber  diaphragm  K  rests  against  a  disc  S,  forming  an 
air  motor  at  /.  By  means  of  a  side  tube  air  is  brought  to  the 
valve  L  from  C.  The  valve  L  is  adjustable,  so  that  the  amount 
of  air  admitted  into  the  space  /  may  be  fixed.  M  is  the  outlet 
to  this  space,  closed  by  the  valve  N.  N  is  fastened  to  the  lid, 
which  is  controlled  by  a  bent  piece  of  metal  0.  This  piece  is 
fastened  rigidly  to  the  block  R  at  one  end,  but  the  other  end 


FIG.  210. — Mechanism  of 
Johnson  Thermostat. 


302 


ELEMENTS  OF  HEATING  AND  VENTILATION 


is  free  to  move  and  operate  the  seat  N.  The  strip  is  composed 
of  strips  of  steel  and  brass  and  bends  as  its  temperature  changes, 
due  to  a  difference  in  the  co- 
efficients of  expansion  of  the  two 
metals.  The  strip  will  move  to 
the  right  with  a  fall  in  tempera- 
ture and  this  will  close  the 
valve  N,  causing  the  pressure 
in  /  to  increase  until  it  is  suffi- 
ciently great  to  move  the  piston 
5  and  the  lever  T,  thus  moving  F 
and  /  to  right  and  closing  the  | 


FIG.  211. — Johnson  Regulator. 

opening  from  C,  the  springs  causing  the  motion  of  F  to  be  rapid 
when  it  occurs.     The  steam  valve  now  opens  as  air  leaks  from 


TEMPERATURE   CONTROL  AND  DRYING  BY  AIR       303 


D  and  after  the  room  becomes  hot  O  moves  to  the  left;  air  leaks 
from  M  and  L,  S  moves  to  the  right,  moving  H,  G,  and  F  to  the 
left.  This  allows  air  to  enter  D  and  shuts  off  the  valves  on  the 
radiator.  The  turning  of  the  screw  at  U  operates  on  the  spring 


X  and  so  fixes  the  temperature  at  which  0  will  open  the  valve  N. 
This  system  as  here  described  is  applied  to  any  number  of  ther- 
mostats. A  compressed-air  main  is  connected  to  all  of  the  ther- 
mostats and  these  connect  the  air  to  a  group  of  radiators  in  a 
room.  The  same  system  may  be  applied  to  regulate  dampers  or 
coils  in  indirect  heating,  as  will  be  described  in  the  next  system. 


304         ELEMENTS  OF  HEATING  AND  VENTILATION 


TEMPERATURE  CONTROL  AND  DRYING  BY  AIR   305 


The  external  appearance  of  the  thermostat  is  shown  in  Fig 
211.  The  hole  at  the  bottom  is  for  the  key  adjustment  for  the 
temperature  at  which  action  takes  place. 

The  Powers  system,  as  applied  to  a  plant  using  radiators 
for  the  heat  loss  and  tempered  air  for  ventilation  so  that  the  air 
for  all  rooms  is  at  the  same  temperature,  is  given  in  detail 
in  Fig.  212.  It  consists  of  motor-driven  air  compressor  A  and 
storage  tank  B  connected  by  pipes  to  a  series  of  thermostats 
C,  and  the  thermostats  are  then  connected  by  pipes  to  the 
motor  valves  G,  G  and  G  and  the  damper  operator  M.  The  ther- 


FIG.  214. — Powers  Thermostat. 

mostat  allows  air  to  enter  the  casing  at  the  top  of  the  valves 
G  when  the  temperature  is  high  and  this  air  presses  against  a 
diaphragm  attached  to  the  valve  stem,  closing  the  valve,  as 
described  before.  The  thermostat  on  the  side  of  the  tempered 
air  duct  is  heated  by  the  metal  of  the  case  and  operates  the 
relays  H,  by  which  the  valves  on  the  various  coils  are  thrown 
into  action  in  succession,  the  action  of  the  air  when  thrown  on 
by  the  hot  thermostat  immediately  opening  the  damper  7  by- 
passing the  coil  and  then  shutting  down  the  sections. 

Fig.  213  illustrates  a  single-duct  system  of  indirect  heating. 
The  fan  B  draws  air  through  the  tempering  coil  A,  sending  part 
of  it  through  the  main  coil  C  and  part  beneath  the  coil  into 
the  tempered  air  chamber  D.  The  thermostat  E  keeps  the  tern- 


306 


ELEMENTS   OF  HEATING  AND  VENTILATION 


perature  at  the  right  point  by  acting  on  the  by-pass  damper 
through  the  diaphragm  motor  and  by  acting  on  the  coils  A 
through  the  diaphragm  valves. 


FIG.  215. — Powers  Damper  Regulator. 

The  thermostats  G  in  the  rooms  act  on  the  diaphragm  motors 
H  and  operate  the  mixing  dampers,  cutting  off  the  hot  air  when 


TEMPERATURE   CONTROL  AND   DRYING  BY  AIR       307 

more  tempered  air  is  needed.     Each  room  will  have  a  diaphragm 
motor  acting  on  the  mixing  chambei  dampers  for  its  line. 

The  motor  part  of  the  thermostat  consists  of  a  hollow  cor- 
rugated vessel  filled  with  a  volatile  fluid.  The  frame,  Fig.  214, 
of  the  apparatus  is  covered  with  a  casing  to  protect  the  motor 
parts.  The  pointer  is  attached  to  a  screw  which  so  moves  the 
frame  that  a  higher  temperature  is  required  for  the  volatile 
fluid  to  produce  sufficient  pressure  to  operate  the  two 
valves. 


FIG.  216. 
Honeywell  Thermostat. 


FIG.  217. 
Honeywell  Solenoid  Regulator. 


Fig.  215  illustrates  a  method  of  using  this  corrugated  vessel 
to  produce  the  pressure  to  operate  a  diaphragm  regulator.  The 
metal  casing,  12  ins.  diameter,  has  a  corrugated  partition  within 
it,  the  space  on  one  side  containing  a  volatile  liquid.  When 
this  heats  to  a  definite  temperature  some  of  the  liquid  volatilizes 
and  compresses  the  air  on  the  other  side  of  the  diaphragm  and 
this  acts  on  the  water  seal  on  top  of  the  rubber  diaphragm  of 
the  motor  below  and  forces  the  lever  down.  In  this  way  boiler 
draft  or  furnace  draft  may  be  regulated.  The  temperature 


308 


ELEMENTS   OF  HEATING  AND  VENTILATION 


around  the  vessel  fixes  the  amount  of  volatilization  and  thus 
the  position  of  the  lever.  For  controlling  heaters  or  furnaces 
the  Honeywell  and  the  Minneapolis  systems  may  also  be  used. 

The  Honeywell  temperature  regulator  consists  of  a  ther- 
mostat, Fig.  216,  in  which  the  relative  expansion  of  two  dissimilar 


FIG.  218. — Honeywell  Regulator. 


metals  causes  a  strip  to  touch  one  of  the  contact  points,  the  tem- 
perature at  which  the  change  from  one  to  the  other  occurs 
depending  on  the  position  of  the  pointer  at  the  bottom.  This 
thermostat  operates  a  solenoid,  Figs.  217,  218,  on  the  damper 
motor.  If  the  temperature  is  high  one  point  touches  and  the 
current  causes  the  solenoid  to  lift  the  pawl,  and  a  weight  on  a 
chain,  Fig.  218,  will  cause  the  wheel  to  rotate,  closing  the  draft 


TEMPERATURE  CONTROL  AND  DRYING  BY  AIR   309 

and  opening  the  check.  The  driving  weight  in  this  system  has 
to  be  pulled  up  at  intervals.  This  system  is  governed  by  one 
thermostat  which  is  placed  in  the  living  room  or  one  of  the  rooms 
which  will  have  a  fair  average  temperature.  The  system  is 
simple  and  not  expensive  to  maintain  or  control. 


FIG.  219. — Minneapolis  Regulator. 

In  the  Minneapolis  heat  regulator  the  thermostat,  Fig.  221, 
releases  a  pawl  on  a  clock  which  then  revolves  a  driving 
wheel  one-half  revolution.  The  clock  mechanism,  Fig.  220,  is 
such  that  the  pawl  is  controlled  by  one  point  of  the  two  contact 
points  during  one-half  of  the  revolution  while  the  other  one  con- 
trols the  other.  Thus,  in  Fig.  219,  the  position  of  the  clock 
motor  corresponds  to  the  high  temperature  contact  as  the  check 
damper  is  open  and  the  draft  is  closed  on  a  hot-air  furnace. 


310 


ELEMENTS  OF  HEATING  AND  VENTILATION 


If  the  room  gets  chilled  the  thermostat.  Fig.  221,  touches  on  the 
other  point  and  the  cranks  are  moved  through  one-half  of  a  rev- 
olution. These  last  two  systems  are  applied  with  one  thermo- 
stat for  the  heater  at  some  central  point. 

In  residences  the  doors  are  mostly  open  during  the  day,  and 
hence  for  such  this  single  thermostat  is  satisfactory.  Such 
apparatus  is  of  value  for  night  heating  where  perishable  objects 


FIG.  220. — Minneapolis  Thermostat  and  Motor  Works. 

are  in  rooms.  Fig.  222  illustrates  the  application  of  the 
sylphon  bellows  A  to  a  thermostatic  control  of  temperature  in 
a  tank.  The  bellows  A  is  connected  by  a  tube  B  to  the  closed 
tube  C,  the  whole  system  containing  a  volatile  hydrocarbon. 
When  the  temperature  is  low  in  the  tank  the  weight  D  opens 
the  valve  and  permits  the  steam  to  enter  the  heating  coils. 
Then  as  the  temperature  rises  the  vapor  pressure  from  the  liquid 
in  C  increases  and  pushes  down  on  the  valve,  shutting  off  the 


TEMPERATURE  CONTROL  AND  DRYING  BY  AIR       311 

steam   supply.      By  moving   the  weight  various  temperatures 
may  be  obtained  in  C. 

Drying.  The  use  of  air  for  drying  such  things  as  bricks, 
lumber,  woven  goods  or  any  other  article,  is  one  which  warrants 
considerable  attention. 


FIG.  221. 
Minneapolis  Thermostat. 


FIG.  222. 
Sylphon  Thermostat  Regulator. 


If  air  is  heated  its  capacity  for  moisture  increases  because 
the  weight  of  a  cubic  foot  of  moisture  is  greater  at  a  higher 
temperature.  Each  cubic  foot  can  be  occupied  by  air  and 
moisture,  each  constituent  sustaining  part  of  the  atmospheric 
pressure.  If,  for  instance,  air  saturated  with  moisture  at  60° 
F.  is  heated  to  120°  F.,  this  air  can  hold  more  moisture  because 
moisture  at  120°  F.  occupies  less  space  than  that  at  60°  F.,  as 
it  is  under  a  greater  pressure  of  saturation.  Moisture  at  60° 
is  under  0.20  Ib.  pressure  and  weighs  5.8  grains  per  cubic  foot, 


312         ELEMENTS   OF  HEATING  AND  VENTILATION 

while  at  120°  F.  the  pressure  is  1.69  Ibs.  and  the  weight  is  34.5 
grains  per  cubic  foot.  This  means  then  that  in  time  the  air 
could  absorb  more  than  five  times  the  original  amount  of  mois- 
ture and  carry  it  away  from  the  article  from  which  it  absorbed 
the  moisture. 

It  must  be  remembered  that  this  evaporation  of  water 
requires  heat,  and  although  the  hot  air  can  take  it  up  this  act 
will  cool  the  air  unless  there  is  a  certain  amount  of  heat  supplied 
from  some  source.  This  cooling  action  reduces  the  temperature 
of  the  air  and  with  it  its  capacity  for  moisture.  It  is  to  be  remem- 
bered that  moisture  will  always  enter  any  space  until  there  is 
enough  present  in  that  space  to  saturate  it  at  the  given  tem- 
perature. It  is  absolutely  independent  of  the  presence  of  the 
other  substances  in  the  space.  Moisture  when  present  will  exert 
the  pressure  corresponding  to  its  temperature.  The  cooling 
action  is  the  feature  of  air  conditioning  used  in  summer  weather. 
To  illustrate  these  principles — suppose  that  bricks  at  a  tem- 
perature of  80°  weigh  when  wet  600  Ibs.  and  that  water  is  20 
per  cent  of  this  weight.  The  problem  is  to  find  how  much  air 
is  required  to  dry  this  if  the  air  is  heated  to  190°  by  exhaust 
steam  in  a  coil  when  taken  from  the  atmosphere  in  which  the 
dry-  and  the  wet-bulb  readings  are  70°  and  65°  respectively. 

From  Fig.  19,  for  air  at  70°  with  a  5°  drop  for  the  wet  bulb 
the  relative  humidity  is  77  per  cent  and  the  moisture  content 
is  6.4  grains  per  cubic  foot. 

If  now  the  air  and  its  moisture  are  cooled  to  t°  F.  when  the 
necessary  heat  is  given  up  to  warm  the  clay  and  its  water  and 
to  evaporate  the  water,  the  heat  thus  removed  per  cubic  foot 
entering  is 

Mcp(i<)o-t)+mc-p3(igo-t),      ....     (165) 

where   M  =  mass  of  i  cubic  foot  of  entering  air; 
Cp  =  specific  heat  of  air; 

w  =  mass  of  moisture  in  i  cu.ft.  of  entering  air; 
cps  =  specific  heat  of  steam ; 
t  =  temperature  of  mixture. 


TEMPERATURE   CONTROL  AND   DRYING  BY  AIR       313 
Now 

M= 


pt  =  barometric  pressure  ; 

pm  =  pressure  from  moisture  or  vapor  tension 

=  steam    pressure    at    7o°Xrel.    humidity     (approxi- 
mately). 


m  =   .4  grans,  0.0009     .  at  70°,  or    . 

=  0.0007  at   190°. 
The  heat  removed  from  the  brick  per  cubic  foot  of  air  is 

M'c(t-6o)+nM'(t-6o)+nM'r.    .     .    ,     .     (167)' 

M'  =  weight  of  bricks  per  cubic  foot  of  hot  air; 
c  =  specific  heat  of  material  ; 
w  =  per  cent  of  weight  which  is  water; 
r  =  heat  of  vaporization. 

The  moisture  nM  '  should  be  sufficient  to  saturate  the  air  at  the 
temperature  t.  This  air  will  not  occupy  the  original  volume, 
as  the  temperature  is  increased  and  the  pressure  is  decreased. 
Both  of  these  actions  cause  the  volume  of  the  air  to  increase. 
If  the  quantity  of  air  is  too  great  the  discharged  air  will  not  be 
saturated,  while  if  the  quantity  is  driven  through  at  a  low  rate 
it  will  become  saturated  and  this  will  continue  until  all  the 
moisture  is  removed.  The  following  equations  must  therefore 
hold  when  the  leaving  air  is  saturated. 

—  t)-}-mcps(igo  —  t)  =  M'c(l  —  6o) 

+nM'(t-6o)+nM'r.     .     (168) 


(P*  ~Pm 
nM  =77  —  .    w  f-       —  ^mi—m.       .     .     .     (169) 


pmt  —  vapor  tension  for  saturation  at  temperature  t\ 
mt  =  weight  of  moisture  per  cubic  foot. 

In  these  two  equations  M'  and  /  are  unknown,  and  by  trial 
the  resulting  values  can  be  found.     The  best  method  is  to  assume 


314          ELEMENTS  OF  HEATING  AND  VENTILATION 

t  and  solve  for  Mf  in  each  equation.  When  t  is  so  assumed  that 
the  two  values  of  M'  are  the  same  the  value  will  be  the  correct 
ones. 

M  =  144(14^7  -0.77X0.363) 

650X53.37 
^  =  0.239; 

cPS  =  o.S'} 
0  =  0.2; 
assume 

/  =  i5o; 
0.06X0.239X40+0.0007X0.5X40 

£Jlf'X  1007.2; 


M'  =         =  .  00247  lb-; 

237 


.7  -Q-77  Xo.363)(6io) 

T—  -^7^  —  r  -  0.01032—0.0007 

(14.7-3-  7  1  5)  (S3o) 


If  now  the  temperature  be  made  smaller,  Mf  from  the  first  equa- 
tions will  be  larger  and  that  from  the  second  will  be  smaller. 
Suppose  100°  is  used;  this  gives  as  the  two  values  of  M'\ 

M'  =  0.0058; 
JW'  =  0.0123. 

A  smaller  value  will  give  the  correct  amount.  Suppose  85°  is 
tried;  the  values  are: 

Mf  =  0.00705; 
M'  =  0.0061. 
For  90°  F.: 

,¥'  =  0.00668; 
M  '=0.00790. 

By  sketching  the  curves  assumed  to  be  straight  lines  between 
the  last  two  values  as  shown  in  Fig.  223,  the  values  of  M  and 
t  at  the  points  of  intersection  are  found  to  be  £  =  87.0°  and 
Af'=o.oo69~respectively.  This  shows  that  the  air  at  190°  F. 


TEMPERATURE  CONTROL  AND  DRYING  BY  AIR       315 


is  cooled  to  87°  F.  by  the  drying  action  and  that  each  cubic 
foot  of  air  will  dry  0.0069  lb.  °f  brick  'material  and  will  leave 
at  87°  F.  The  total  quantity  for  air  required  will  then  be 


cubic  feet  air  = 


600 
0.0069 


=  87,000  cu.ft. 


Of  course  if  this  remains  here  after  the  moisture  is  driven  out 
the  brick  will  warm  up  and  probably  leave  at  190°  F.  This  will 
change  the  problem  somewhat,  in  that  the  amount  of  air  will 


/M«.005 


M  0.004 


t!15 


FIG.  223.  —  Method  of  Finding  Values  of  /  and  M'. 


have  to  be  increased, 
put  in  the  form: 

Mcp(igo  — 


The  equation  first  used  might  have  been 


—  f)  = 

Mfc(igo  -  60)  +nM'(t  -  60)  +nM'r     (i  70) 


Problems  similar  to  this  may  be  handled  for  drying  any  kind 
of  substance.  A  -similar  method  may  be  used  to  investigate 
the  exhaust  gases  from  a  boiler  or  from  kilns  to  find  whether  or 
not  this  gas  will  be  sufficient  to  dry  the  material  from  the  clay 
presses.  The  heat  and  moisture  content  of  the  gases  in  the  hot 
and  cold  condition  are  considered  in  connection  with  the  heat 
to  be  added  and  the  moisture  to  be  removed  from  the  wet 
material. 


INDEX 


Absolute  humidity,  20 
Air,  20 

allowance,  23 
,  changes  per  hour,  23 
cooling,  43 
duct,  257 
,  flow  of,  187 
,  free,  20 
line,  145 

per  hour  per  person,  23 
,  properties  of,  38 

space,  58 
,  tempered,  12,  13 

valve,  101,  145 
,  vitiated,  21 
Allen,  in 

automatic  air  valve,  101 
American  District  System,  285 
Radiator  Co.,  74,  in 
Anchors,  136 
Anemometer,  204 
Angle  valve,  92 
Arch,  51 

Area  flues,  176,  207,  208,  231 
Area  pipes,  86,  138,  141,  163,  207,  208 
Argon,  20 
Asbestos,  146 
Auto  valves,  96,  98 

B 

Barrus,  146 
Base  ring,  256 
Bends,  281 
Billings,  26 
Blast  area,  220 
Boiler,  2 

,  locomotive,  268 

,  sectional,  262 
sizes,  271-2 
size  determinations,  274-5 


Boltzman,  106 
Bonnet,  242,  243,  259 
Book  tile,  62 
Boots,  i,  244 
Bottomley,  105 
Bottom  support,  75 
Boxes,  178 

for  registers,  243-6 
Box  radiators,  76 
Branch,  3,  155 
Bricks,  58 

,  Haverstraw,  58 

,  hollow,  58 

British  thermal  unit,  45 
Buffalo  Forge  Co.,  117 

coils,  86,  115-117 
,  size,  185 
,  loss  in,  215 
By-pass  plate,  256 


C,  values  of,  49 

Calculations,  boiler  size,  289 

coefficient  K,  53 
,  direct  heating,  148 
,  district  system,  289 
,  fans,  223 
,  flue  size,  210 
,  furnace  heating,  249,  274 
,  furnace  size,  273 
,  heat,  118 

,  hot- water  system,  169 
,  indirect  heating,  171 
,  mill  heating,  227 
,  natural  draft,  178 
,  pipe  size,  139 
,  plenum  system,  183-228 

Calorie,  45 

Carbon  dioxide,  20 

apparatus,  24 
bottle,  25 

317 


318 


INDEX 


Carbon  dioxide,  exhaled  per  person,  22 
,  permissible  amount  21 

Car  heating,  298 

Carpenter,  R.  C.,  69,  in,  139 

Carpenter's  rule,  69,  253 

Carrier,  W.  H.,  32 

Carrier's  air  washer,  39 

Casing,  i,  257 

Ceiling,  flush,  60 
plates,  135 
values  of  K,  65 

Cellar  plan  for  direct  heating,  150 
for  hot-air  furnace,  250 
for  hot  water,  170 
for  indirect  heating,  177 

Changes  of  air  per  hour,  23 

Chases,  144 

Chezy's  formula,  142 

Chimneys,  274,  276 

Circulation,  sluggish,  129 

City,  district  heating  of,  295 

Clapboards,  58 

Coefficient  of  transmission,  48 
»  C,  49 
,d,  51 

i  e>  5i 

K,  64-65 
Coils,  86,  88 

corner,  85 
main,  174 
miter,  92 
resistance,  9 
size,  185 
tempering,  174 
Cold-air  duct,  252 
pit,  256 

supply,  238,  253 
Collars,  245 

Combustion  chamber,  255 
Complete  circuit  system,  129,  157 
Concealed  work,  145 
Concrete,  value  of  K,  64  \ 
Conduction,  46 

constant,  47 
Conduits,  282-4 

,  loss  from,  288 
Connections,  2,  132 

,  branches,  155,  137 
,  radiators,  132,  145 
Constant  of  conduction,  47 

of  transformation,  45 
Convection,  46 
Cooling  air,  43 
Cork,  146 


Corner  coils,  85 

valves,  96 

Corrugated  pipes,  281 
Cost  of  installing,  293 
of  operation,  293 
Covering,  287 

,  block,  148 
,  pipe,  146 
,  plaster,  148 
,  saving  from,  148 
,  sectional,  148 
,  value  of,  147 

Cox,  Abram,  Stove  Co.,  261 
Cubic  feet  per  sq.ft.  radiation,  131,  159 
Curves,  cooling  air,  43 

,  equivalent  pipes,  200 

,  friction  factors,  196 

,  heating  value  of  coils,  112-116 

,  method  of  solving  equations, 

315 

,  moisture  in  air,  29-32,  37 
,  pressure  in  fans,  219 
,  relative  humidity,  29-32,  37 
,  temperature  from  coils,    12-116 
,  values  of  heat  loss  from  con- 
duits, 289 
Cut-off  plate,  256 

D 

Dalby,  106 
Damper,  13,  178,  234 

,  when  omitted,  245 
Design,  district  mains,  288 
,  direct  heating,  148 
,  hot-water  heating,  169 
,  indirect  heating,  171,  227,  183- 

228 
Determination  of  K,  1 10 

,  fan  size,  223 
,  pipe  size,  139 

Development  of  building,  134-151 
Dew  point,  26 

apparatus,  26 
Direct  heating,  127 
Direct-indirect  heating,  8 

radiator,  76,  7 
Direct  radiation,  i,  4,  127 
Distributing  main,  2,  129 
Distributors,  O.  S.,  158 
District  heating,  279 

,  value  of,  296 
Dome,  i 

Double  ducts,  13 
Down  takes,  75 


INDEX 


319 


Drip  pots,  143 

Drop,  pressure,  193 

Drying,  309 

Ducts,  12,  178 

,  single  system,  14,  173,  214 

,  double  system,  13,  174,  210,  213 

Dulong,  105 

Dynamic  pressure,  191 


Eccentric  fittings,  154 

Effect  of  exposure,  68 

of  intermittent  heat,  68 

Elbows,  247 

,  resistance,  140 

Electric  heating,  8 
meter,  206 
radiators,  9 

Eliminator,  40 

,  glass  surface,  253 

Equivalent,  lengths,  197 
,  pipes,  197 
,  temperatures,  71 
,  volume,  253 

Evans,  290 

Evaporation  requires  heat,  310 

Excelsior  indirect  radiator,  90 

Expansion  apparatus,  281 
joints,  138,  281 
of  pipes,  138 
tank,  165 

Exposure  factor,  68 


Factory  heating,  233 
Fan  blowers,  6,  8 
Fans,  6,  8,  216 

,  dimensions,  221 

,  power  for,  221 

,  power  capacity  and  speed,  223 

,  pressure  from,  217 

,  tables  for,  225,  226 

with  furnace,  249 
Ferrel,  28 
Filters,  41 
Fire  pot,  i,  255 
Fire  proof  floor,  69 
Flat  arch,  61 
Floors,  59 
Floor  box,  243 
plate,  135 

,  slow  burning,  60 

,  reinforced  concrete,  60 


Floor  tile  arch,  61 
,  values  of  K,  65 

and  ceiling  vent,  10 
Flow  of  air,  187 
of  steam,  141 
of  water,  290 
,  main,  2,  153-4 

Flue  area,  175,  207,  208,  210,  231 
radiator,  76 
smoke,  274-6 
velocities,  210 
Flues,  240 

Forced  circulation,  171 
Free  air,  20 
French  windows,  1 23 
Friction  coefficient,  195 
factor,  195-6 
loss,  192 
loss,  table,  208 
Fuller,  Warren  &  Co., 
Furnace,  hot-air,  i,  255 
heating,  i,  237 
position,  250 
,  size,  determination,  273 
,  size  of,  253,  269,  270 
,  with  fan,  249 
Furred,  58 
Furring  strips,  58 


Gauge  metal,  179 
Generator,  Honeywell,  166 
Gib  panel,  80,  252 
Gifford,  294 

Glass  area,  equivalent,  253 
Glower,  luminous  radiator,  9 
Goverment  tile,  62 
Graff  Co.,  255-7 
Grashof,  49,  51 

H 

Hair  felt,  146 
Hammering,  128 
Hangers,  136 
Haven,  290 
Head,  loss  of,  190 

,  total,  197        . 
Heater,  2 

,  loss  of  pressure  in,  214 

,  main,  174 

,  positivflo,  88 

,  sectional,  262 

,  tempering,  174 

,  Vento,  89 


320 


INDEX 


Heat  for  ventilation  air,  69 
from  lights,  70 
from  motors,  70 
from  persons,  70 
Heating  direct  steam,  127 
district,  279 
furnace,  237 
hot  water,  153 
indirect,  171 

surface  per  cubic  foot,  131, 159 
surface   required   for  natural 

draft  stacks,  176 
systems,  merits  of,  276 
Heat  loss,  45 

with  covered  pipes,  147 
through  walls,  47,  69 
stacks,  i 
transmission    through    radiators, 

105 

Helium,  20 
Hoffman,  242 
Honeywell  Co.,  163 

generator,  166 
temperature  regulator, 

306 

valves,  164 

Horse-power  for  blowing,  208 
Hot-air  furnace,  i,  255-262 

heating,  237 
Hot- water  heating,  153 
radiators,  75 
House  plans,  122 
Housing,  217,  218 
Humidifiers,  39 
Humidity,  26 

,  absolute,  20 
,  relative,  20 

Humphrey  gas  heater,  267 
Hydraulic  radius,  142 
Hydrodeik,  30 
ygrometer,  26 


> 


1  Junior  heater,  265 
Indirect  heaters,  transmission,  in 
heating,  171 

,  calculations,  171,  183, 

228,  178 
radiators,  90-92 
systems,  5 

Inside  circulation,  239 
Intermittent  heat  factor,  68 
Isometric  drawing,  132 


Jenkins  Bros,  valves,  94 
Johnson's  system,  300 


K 


Kelsey  Co.,  259 
Kinealy,  67 
Krypton,  20 


Lambrecht  polymeter,  31 

Lath,  58 

Law,  Stefan  Boltzman,  106 

,  Stewart  Kirchhoff,  106 
Leader,  i,  240,  243 
Leakage,  n 

air,  46 

Leg,  detachable,  81 
loops,  8 1 
section,  75 
,  vertical,  130 

Libra  automatic  air  valve,  102 
List  price,  86 

Lock  and  shield  radiator  valve,  96 
Loops,  74 

Loss  from  conduits,  288 
ducts,  232 
water  pipes,  290 
of  head,  190,  192 
of  heat,  45 
of  pressure,  214 
Luminous  radiator,  9 
Lunge,  26 

M 

Magnesia,  146 
Main,  127,  128 
Manholes,  284 
Masonry,  values  of  K,  64 
Massachusetts  fan  coils,  86 

fans,  216 
Measurements,  radiators,  83 

,  Vento  heaters,  90 
Metal  gauge,  179 
Metargon,  20 
Meter,  electric,  206 

,  oscillating,  297 

,  Venturi,  204 
Mill  heating,  233 

or  slow-burning  construction,  60 
Mills  system,  129 
Mineral  wool,  146  1 
Minneapolis  temperature  regulator,  307 


INDEX 


321 


Miter  coil,  92 

Modulation  valve,  96,  98 

Moisture,  26 

Monash  value,  100 

Monthly  percentage  of  heat,  294 

Motor  discharge  valve,  99 

N 

Natural  draft  circulation,  171 
Neon,  20 
Newton,  105 
Nicholson,  106 
Nipples,  hexagon,  89 

,  push,  264 
Nitrogen,  20 
Norwall  automatic  air  valve,  103 

packless  valve,  92 
Numbers,  designating,  119 


Offset  fittings,  154 
Offsets,  247 
Orifice,  standard,  202 
O.  S.  connector  or  distributors,  158 
Outlets.  163,  168 
,  size,  132 

Overhead  system,  129  , 

Oxygen,  20 
Ozonator,  14 
Ozone,  14-19 


Packless  valves,  92 
Partial  pressure,  28 
Partitions,  63 

,  values  of  K,  65 
Paschen,  105 
Paul  system,  145 
Perfection  pin  radiator,  92 
Peripheral  speed,  217-220 
Personal  amount  of  air,  23 

exhalation  of  CO2,  22 
Petavel,  105 
Petit,  105 
Pettenkofer,  21 

Pettersson's  CO2  apparatus,  24 
Phenolphthalein,  26 
Pierce  Co.,  264 
Piezometers,  190 
Pipe  coils,  84 

coil  radiators,  82 

,  concealed,  144 

covering,  146 


Pipe,  double  system,  128 
,  exposed,  144 
,  full  weight,  297 
,  list  price,  86 
,  single  system,  127 
,  size  of  hot- water,  159 
,  sizes,  86 
,  wrought  iron,  86 
Pitch  of  hot-air  pipes,  244 
of  steam  pipes,  143 
Pitot  pressure,  191 

tubes,  191 
Plate  warmers,  81 
Plenum,  8,  171 
Pockets,  128,  144 
Polymeter,  31 
Positivflo  heater,  88 
Power  for  fans,  221 
Powers  system,  302 
Pressed  steel  radiator,  82 
Pressure  in  fans,  217 

dynamic,  191,  217 
loss  of,  191-3 
measures  of,  188 
partial,  28 
Pitot,  191 
saturation,  29 
static,  191,  217 
velocity,  191,  217 

Properties  of  dry  and  saturated  air,  38 
Psychrometer,  27 

R 

Radiation,  46 

from  conduits,  288 
Radiator,  i,  73,  255 
,  circular,  80 

connections,  132,  145 
,  corner,  80 

designation,  135 

dimensions,  83 
,  dining  room,  81 
,  electric,  9 

foot  ups,  82 
,  furnace,  255 
,  heat  transmission,  105,  159 

heights,  80,  83 
,  hot- water,  153 
,  low,  80 

outlets,  132,  163,  1 68 
,  pantry,  81 

pedestal,  82 
,  pipe  coils,  82 
,  pressed  steel,  82 


322 


INDEX 


Radiator  selection,  80,  132 
,  size  required,  131 
table,  149 

tapping,  132,  163-8 
,  test  of,  no 
,  values  of  K, no 
,  wall,  81 
,  window,  80 
Radifier,  100 
Rate  of  transmission,  47 
Recirculating  duct,  237 
Reducers,  144 
Register,  i 

Register  box,  243,  246 
faces,  179,  209 
location,  329 
,  special,  247 
Reheater,  1 2 

Reinforced  cinder  concrete  floor,  60 
Relative  humidity,  20,  26 
Resistance,  valves  and  elbows,  140 
Return,  3 

for  different  buildings,  130 
,  size  of,  142 
Reitschel,  H.,  47,  49 
Right  and  left  nipples,   73 
Risers,  i,  2,  127,  128 

,  arrangement  of,  134 
control,  135 
designation,  135 
table,  149 

Rococo  wall  radiator,  81 
Rosetti,  105 
Rudd  gas  heater,  268 


Sand  ring,  259 
Saturation,  20 

pressure,  29 
School  building,  180 
heating,  248 
Screens,  252 
Sealed  return,  130 
Sections  of  boiler,  264 
Sheathing  boards,  58 
Shingles,  58 
Shoes,  i,  244 
Sickels,  139 
Single-duct  system,  14 
-flow  system,  153! 
-pipe  system,  127 
Size  of  flues,  179 

furnace,  253 
mains,  138,  141,  163 


Size  of  pipes,  hot- water,  159 

supply  and  return,  187 

Vento  heater,  186 
Skew  backs,  61 
Sleepers,  60 
Sleeves,  136 
Sling  psychrometer,  27 
Slow-burning  construction,  60 
Smoke  flue,  274-276 

outlet,  256 

Sodium  carbonate,  26 
Spangler,  119 
Spence  boiler,  265 
Stacks,  i,  5,  8,  240 
Stateroom  type  electric  radiator,  9 
Static  pressure,  191 
Steam  flow,  141 

pipes,  pitch  of,  143 
Stefan,  105 

Stefan-Boltzman  Law,  106 
Sterling  Radiator,  92 
Stove  cement,  259 
Studs,  58 
Sturtevant,  B.  F.  &  Co.,  86 

coils,  86 

Supports,  282-4 
Swinging  ells,  137,  281 
Sylphon,  94 

air  and  vacuum  valves,  104 
air  valve,  103 
packless  radiator  valve,  94 
vent  valves,  104 


Tables,  air  per  person, 

,  properties,  38 
i  velocity,  209 
,  boilers,  271-2 

,  Buffalo  Forge  Co.  heater,  185 
,  capacity  pipes,  138 
,  coefficients,  64,  65 
,  conversion  factors,  45-6 
,  covering  loss,  147 
,  cubic  feet  per  square  foot  heat- 
ing surface,  131,  159 
,  equivalent  pipes,  208 

temperature,  72 
,  expansion  of  pipes,  138 

tanks,  165 

,  exposure  allowance,  68 
,  fans,  225-6 
,  friction  factor,  196-7 
,  loss,  208 


INDEX 


323 


Tables,  furnace  heating,  238,  251 
,  size,  269-70 

,  gauge  thickness,  179 
,  heat  changes,  294-6 
,  heaters,  186,  187 
heat  given  out,  70 

transmission  coefficient,  64, 

65 

,  house  heating,  120-1 
,  indirect  heating,  178 
,  loss  pressure  in  heaters,  215 
,  pipe  sizes,  air,  207 

,  steam,  86,  138,  141 
,  water,  163 
,  pressure,  207 
,  properties  of  air,  38 
,  radiator  list,  149,  170 
,  radiators,  81,  83 
,  riser  list,  149,  170 
,  room  temperature,  66-7 
,  school  building,  181 
,  size,  iron,  179 

,  pipes,  86, 138, 141, 163,  207 
,  risers,  135 
,  tin,  247 

,  tappings,  132,  163,  1 68 
,  temperature  effect,  209 

rooms,  66-7 
,  tin  sizes,  247 
,  Vento  heater,  186 
,  velocity,  20,  209 
.  water  weight,  143,  161 
Tank,  expansion,  165 
Tappings,  radiator,  163-8 
Temperature  allowance  for  height,  68 
atmosphere,  66 
control,  300 
,  effect  of,  198 
,  entrance,  172 
,  equivalent,  71 
,  inlet,  237 
,  maximum,  on  hot  water, 

166 

outlet  from  heater,  112 
rooms,  66 

Tempered  air,  12,  13 
Test  of  radiator,  no 
Theatre  heating,  235 
Thermal  units,  45 
Thermmograde  system.  96 
Thermostat,  300,  303,  308,  312 
Thermostatic  motor,  13 
Thickness  of  flues,  179 
Thomas,  206 


Tiles,  hollow,  58 

Tin,  size  of,  247 

Tongued  and  grooved  boards,  58 

Top  guide,  75 

Total  head,  197 

Transformation  fact  rs,  45 

Transmission,  rate  of,  47 

coefficient,  48 

of  heat  through  radiators, 

105 

Traps,  use  of  for  buildings  on  same  re- 
turn, 130 
Tunnel,  282 
Two  ducts,  13 
Two-pipe  system,  128 


Vacuum  system  of  heating,  1 29 

of  ventilation,  8,  171 
valves,  103-4 
Valves,  92 

,  air,  101,  102 
,  corner,  96 
,  lock  and  shield,  96 
,  Monash,  108 
,  motor  discharge,  99 
,  positions  of,  144 
,  0-  O.  water,  95 
,  resistances,  140 
,  sylphon  packless,  94 
Vapor  tension,  36 
Variators,  281 
Velocities,  209,  210 
Velocity,  effect  on  transmission,  107 
for  natural  draft,  175 
in  ducts,  183 
in  hot  water-pipes,  159 
pressure,  191 
Vent  flue,  173 

stack,  i,  242 
Vent  values,  104 
Ventilation  for  schools,  181 
,  heat  for,  69 
,  method  of,  1 1 
Vents,  92 
Vento  heater,  89,  90 

,  measurements,  90 
,  size,  1 86 
Venturi  meter,  204 
Vitiated  air,  21 
Volume  equivalent,  253 
Voussoirs,  61 


324 


INDEX 


W 

Wall,  58 

section,  52,  57 
,  type  electric  neater,  9 
,  values  of  K,  64 
,  wooden,  59 
Warren,  Webster  &  Co.,  40,  43 

washer,  40 
valves,  98-9 
Washers,  39 
Water  line,  127 
pan,  261 
vapor,  20 


Water,  weight  of,  143,  161 

Weber,  105 

Wet-  and  dry-bulb  hygrometer,  27 

Williams,  290 

Window  constants,  64-5 

,  French,  123 
Wood  floor,  54 
walls,  59 

,  value  of  K,  65 


Xenon,  20 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 


AN  INITIAL  FINE  OF  25  CENTS 

WILL  BE  ASSESSED  FOR  FAILURE  TO  RETURN 
THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
WILL  INCREASE  TO  5O  CENTS  ON  THE  FOURTH 
DAY  AND  TO  $1.OO  ON  THE  SEVENTH  DAY 
OVERDUE. 


AUG  11  1943 


LD  21-100m.-7,'39(402s) 


YC    12845 


THE  UNIVERSITY  OF  CALIFORNIA  LIBRARY