62 APPLICATION OF THE LAWS OF HYDRAULICS
reason that these furnaces must be so constructed as to prevent the
least possibility of free air getting in on the hearth.
These are chamber furnaces, and the height from the hearth to
the roof may be great. The best furnaces are constructed with a
high arch; the space immediately below it serves as a combustion
chamber, and is very effective in promoting an intimate mixture
of the combustible gases and the air; the combustion of the gas,
therefore, takes place with very nearly the theoretical air supply.
These furnaces are operated with the doors constantly or very
frequently opened. Therefore the height of the charging opening
is the most important dimension and fixes the working quality of
the furnace. This height must be less than the height ht as
indicated by Yesmann's formula.
The Sud-Kama works show an example of a plate-heating
furnace upon the hearth of which there is no inflow of air and
with which, accordingly, they have succeeded in solving the
difficulty of utilizing the waste heat from the furnace in a boiler.
The data for its computation are as follows: the coal consump-
tion per second for one chamber is 0 kg 023. The quantity of gas
per second for theoretical combustion is
Q0 = 4.01X0.023 = 0 m3 092 per second,
Qiooo = 0 m3 429 per second.
The width of the charging opening is 0 m 85.
The height calculated for this opening (according to Yesmann)
ht = hiQQQ, is 0 m 216 and the effective value is 225 mm.
It may be seen by this that the working opening, which is
closed by a door, has a height very well proportioned to the volume
of the gases circulating in the heating chamber. It is for this
reason that the opening of this door, which is operated by a pedal,
does not cause an inrush of cold air into the furnace, as occurs
in furnaces of other systems, for example, in the gas-fired furnace
of the type used at the Alapayewsky works.
The following are the data for these furnaces: the quantity of
wood consumed per compartment or heating chamber per second
is 0 kg 0185. The volume of gas per furnace at 0°, Q0 = 0 m3 082;
at 1000°, Qiooo^O m3 382.
The height of the working door, computed according to the
theory of the inverted weir feiooo = 0 m 164. Nevertheless, the
charging opening is 400 mm in height. This explains why the