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Full text of "The Flow Of Gases In Furnaces"

70

APPLICATION OF THE  LAWS OF HYDRAULICS

Furnace No. 20 ....... fc>  74

21 ....... tt> 58

23 ....... tt> 22

24 ....... k>  70

25

The following example shows the influence of the density of the
medium which the jet of gas penetrates. For Furnace No. 20
the depth H = 1 150 mm at 74.

Determining the depth of the jet at a temperature ti = Q,
there will be obtained

= sin2aX

273+0

- = 864 mm.

-1850-0
Therefore the flame or stream of hot gases does not touch the
hearth, and the distance by which it falls short of so doing is
1150-864 = 286 mm.
Therefore, in these five furnaces, each of 30 tonnes capacity,
selected at random, such a velocity and an inclination have been
given to the gas and the air in the heads that the flame settles to
the hearth when the other portions of the furnace are at a com-
paratively low temperature.
It is evident that perfect repairing of the hearth is assured in
this manner, but that it is not an advantageous arrangement in
the regular working of the furnace. A similar investigation deals
with the circulation of the hot gases in the long furnaces used in
American plants, where the flues in the heads have a very slight
slope and where the velocities are very low for the air and very
high for the gas.
This data has been taken from Professor Pavlow's table for
two 60-tonne furnaces, Nos. 35 and 36.
Making the same assumptions as in the case of the 30-tonne
furnaces, the volume of air at 1000 will be 23 m3 54.per second
and the gas at the same temperature will be 16 m3 88 per
second.
Making the calculations for the temperature U at which it
becomes possible to make bottom in these furnaces, the results
are as follows: