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Full text of "The Flow Of Gases In Furnaces"

MUFFLE FURNACE FOR TEMPERING

173

vertical muffle for continuous service, constructed according to
the designs of the author, was in use at the PoutilofI works (Petro-
grad). In the arsenal the daily interruption of the work resulted
in the rapid wearing out of the muffle, and after a run of two
months it was decided to remove the cast-iron muffle and operate
the furnace with a perforated brick hearth through which waste
gases could pass off. The furnace was reconstructed in this
manner, without a muffle, and upon being placed in operation
worked perfectly, heating very uniformly and fulfilling perfectly
all the demands for annealing and tempering which were made
upon it.

/•sv

FIG. 135.—Cross-section through
Firebox.

FIG. 136.—Cross-section through
Waste Gas Ports.

The following shows the computations which were made:
The volume of the heating chamber, according to the design,
was 3 m3 30;   the temperature of the gas was to be 1000°, the
combustion being neutral, that is to say, without excess air.
The instantaneous  calorific intensity was computed as 2000°,
giving a drop in temperature of the gases of 200° per second, the"
time which the gases remain in the heating chamber being

2000-1000

200

- = 5 seconds.