The Flow Of Gases In Furnaces

184

APPENDIX VI

TABLE 4

CHIMNEY DRAFT (Lange)
BG(l+atQ)

700-fn

700+tn

tgi-

du—do

0.008 to 0.010,

in which F0 = area of bore of chimney at top in square meters;
B — kilograms of coal burned per hour;
G = kilograms of flue gases per kilogram of coal;
a = 1-^273 = 0.00367;
to = temperature of gases at base of chimney;
7 = 1.293 = weight of a cubic meter of air at 0° and 760 mm;
5=ratio between the weight of flue gases and air;
do = diameter of bore of chimney at top;
t? =3.1416 for a circle;
3.3137 for an octagon;
4.00 for a square;
Z = length of flue in meters;
a=flue coefficient 0.03 to 0.14 (usually 0.04);
Hr—height of chimney above grates in meters;
z=mm of water or kilograms per square meter;
71 = weight of flue gases per cubic meter at 0° and 760 mm;
du = diameter of bore of chimney at base in meters
tm—average temperature of flue gases;
p= kilo grams of coal burned per second;
Q=waste gases per kilogram of coal, cubic meters;
un=velocity of gas flow, meters per second (from 3 to 15).