The Flow Of Gases In Furnaces

THE THEORY OF JETS

71

Furnace No. 35
Furnace No. 36

Area of ffas ports
0 m2 7300
0 m2 3935

Velocity of cas at port .....
23 m 11 per sec
4!2 m 90 per sec

Area of air ports ......... ..... • .
2 rn2 70
3 m2 75

Velocity of air at port ................
8 rn 72 per sec
6 m 28 per sec

Slope of gas port ....................
6°
12°

Air port
17°
26°

H = depth of jet = difference in level between sill of gas port and the tapping hole ....................
0 m 92
1 m 00

Average velocity of the mixture by parallelogram ...
llm 80 per ,sec.
20 m 50 per SP *

Average slope of mixture by parallelogram ......................
9° 30'
14° 30'

ti at which the mixture commences to lick hearth .....
1531°
646°

These computations would show that the making of the bottom
in Furnace No. 35 would be difficult, and it is hard to believe that
the design published is correct. (1>

As regards Furnace No. 36, it will be comparatively easy to
make the bottom, and the flame will not be deflected from the
surface of the bath. In the operation of this furnace (No. 36) its
ports will be burned and worn away, their area will be increased
and the velocity of the gas will be accordingly reduced. How
much may the port bo worn away without interfering to an
appreciable extent with the repairing of the bottom?

The formula (F), on page 64, provides the solution of this
problem.

The bottom may be made in a satisfactory manner wheiv
^=1400°; the corresponding value of v may be deduced:

,' v2 sin2 14.5° 273 + 1400

2X9.81

from which v = Q m 20 per second.

X

1850-1400

(1) A great deal of empiricism exists in the arrangement of the heads of
these furnaces, and in many cases the furnaces as they go into operation
differ widely from the drawings. In some plants no two furnaces have
identical heads.