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Full text of "The Flow Of Gases In Furnaces"

DESIGN OF OPEN-HEARTH FURNACES

277

The gas and air necks, the cinder pockets and the uptakes are
next in order. The efficiency of the cinder pocket depends upon
the change in the direction of the flow, as well as upon the reduc-
tion in the velocity of flow. The width of the pockets fixes the
taper of the necks. Both pockets will be made the same width,
say, 2 m 00 (6.56 ft) with a space of 1 m 250 (4.10 ft) between
them. The gas neck will be 3 m 00 (9.84 ft) wide where it leaves
the chamber, tapering to 2 m 00 in a distance of about 3 m 750
(12.3 ft). The air neck will taper from a width of 5 m 00 (16.47 ft)
to 2 m 00 (6.56 ft) in the same distance. These figures have been
fixed arbitrarily and the assumption made that the same or
greater areas will exist than above the checkerwork.


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

Air and gas necks:
	
	
	
	

The frictional resistance will be
	
	
	
	

based on the following:
	
	
	
	

Z/= length of neck    . .
	3 m  750
	4m 000
	
	

S= perimeter average. .  .   .
	9 m 000
	11 m 000
	
	

SL = surface ................
	33.75
	44.00
	
	

co = area in square meters
	5m2   00
	7m2   00
	
	

OJL/ ~f- CO = . .                .                  .                   ....
	6.75
	6 28
	
	

Qt — volume of gases flowing . .
	28m3   75
	45m3   99
	35m3   66
	52m3   08

vt = Qt -:- co = m per sec
	5m    75
	6m    57
	7m    13
	7m    44

Aj = kg per m3 gas ..........
	0.208
	0.239
	0.192
	0.192

7= frictional resistance in kg per
	
	
	
	

0.016X6 75X5.75X0.208 =
	0 kg 129
	
	
	

0 016X6 28X6 57X0 239 =
	
	0 kg 144
	
	

0 016X6 75X6 57X0 192 =
	
	
	0 kg 147
	

0 016X6 28X7 44X0 192 =
	
	
	
	0 kg 144

The gas velocity in the necks is
	
	
	
	

slightly less than in the cham-
	
	
	
	

ber above  the  checkerwork
	
	
	
	

and is assumed the same as in
	
	
	
	

the cinder pockets.   The pres-
	
	
	
	

sure in kilograms per m2 re-
	
	
	
	

quired to impress these veloci-
	
	
	
	

ties on the waste gases will be :
	
	
	
	

5=Aj(w/2-7-20) —kg per m2= . . .
	0.354
	0.525
	0.495
	0.543