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Full text of "The Flow Of Gases In Furnaces"

DESIGN OF OPEN-HEARTH FURNACES
TABLE 16—Continued

263


	Gas on Gas
	Air on Air
	Gas on Waste Gas
	Air on Waste Gas

Weight of checker brick required to store up heat   in waste gas (100° change in brick temperature 70% effective):
 15-minute cycle: Gas [1 791 000 ~(100XO 25)] -7-0 7 =
	
	
	102,350kg
	

Air: [3,164,000 -r (100X0.25)] -v-0.7 =
	
	
	
	180,800kg

20-minute cycle: Gas: [2,388,000 -5- (100X 0.25)] -s-0.7 =
	
	
	136,460kg
	

Air: [4 219 000 -r (100X0.25)] -^0.7 =
	
	
	
	241,100kg

25-minute cycle: Gas [2 985 000 — (100X0 25)] -5-07 =
	
	
	170,600kg
	

Air: [4 974 000 -r (100X 0 25)] -5-0.7 =
	
	
	
	284,300kg


	
	
	
	

Any change in the base assumptions made will alter these
values in a corresponding manner. The change in temperature
of the gas, air and waste gases will vary the quantity of heat
available. The cyclic change in temperature may be varied;
this will change the volume of brick required to store up the heat,
and the surface required for heat interchange. The heat-storage
capacity must be sufficient to supply the desired preheat, as well
as the loss through the chamber walls, when on air or gas. Too
much checker adds to the first cost; too small a checker increases
the operating cost. The conditions will be changed by the use of
other fuels, as well as by changes in the ratio of the air supply.