The Flow Of Gases In Furnaces

232 APPENDIX VII
The brick will weigh about 1800 kg per cubic meter; therefore
the volume occupied will be
Reversal Period
20 Minutes 30 Minutes
1200 Seconds 1800 Seconds
For gas:
20 min. period, 26,667-^1800, cu m...... 14.32
30 min. period, 40,000^1800, cu m............ 22.23
For air:
20 min. period, 63,800-^1800, cu m...... 35.45
30 min. period, 95,680-^1800, cu m............ 53.13
Increase in temp, in checkerwork, degrees Gas Air
Gas: 1200-600=................... 600
Air: 1200-300=...................... 900
Average temp, in checkerwork, degrees:
Gas: (1200+600)^2 =.............. 900
Air: (1200+300) -5-2 =................. 750
Average time in checkerwork, seconds:
At 100° increase in temp, per second. 6 9
At 200° increase in temp, per second. 3 4.5
Gas: Aver, volume per sec, at 900°, m3,
1.75X(l+ai) =................ 7.53
Air: Aver, volume per sec. at 750°, m3,
3.273X (l+at) =....................... 12.28
With 200° per second increase in temp.,
the volume required for the passes will
be, cu m.
Gas: 7.53X3 =................ 22.59
j Air: 12.28X4.5=.................... 55.26
I
With a temperature rise of 100° per second the volume required
for the passes will be double the above.
Fig. 153 shows that with the usual period between reversals
there will be no economy in increasing the thickness of the checker
brick over 2.5 in (63 mm), which is a standard shape.
The volume occupied by the checker brickwork will be the
sum of the brick volume added to the pass volume, and requires
no explanation. With a different producer gas and a different
air proportion there would be a corresponding change in, the
amount of heat interchange required and in the volumes required
for the brickwork and for the passes.
The height of the checkerwork should be made as great as