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Full text of "The Flow Of Gases In Furnaces"

DESIGN OF OPEN-HEARTH FURNACES               215

The wide variety of rules for the proportioning of the regen-
erators affords an ample opportunity for choice, and in part
explains the variation in volume of checkerwork used by different
designers. Empirical rules, basing the proportioning of a part
by a direct ratio with the capacity of the furnace are very easy
to apply, and require very little thought in their use. In addition
they save time, as it only takes a few minutes to arrive at the
regenerator volume required. Unfortunately, this is not the case
when logical methods are employed.

HORIZONTAL  OR VERTICAL PASSAGES
Regenerators may be built with the gas passages arranged
horizontally or vertically. Where head room is limited a hori-
zontal pass regenerator, at first sight, appears to possess certain
advantages, but a consideration of the behavior of heated gases
when cooling and of cold gases when being heated, will show that a
horizontal regenerator or recuperator introduces a considerable
amount of friction in the path of the gases, necessitating an initial
pressure for introducing the air and gas and a strong suction to
remove the waste gases.
At Steelton, Pa., it was found necessary to use a blower
with horizontal regenerators. The writer recently had occasion
to investigate the action of some horizontal regenerators. It was
found that the products of combustion were flowing mainly through
the upper passes and their heat was conveyed to the lower passes
by conduction through the brickwork. The air supply flowed
through the entire height of the checker. The Motional resistance
was excessive. These regenerators, however, contained an
enormous weight of brick for the amount of work to be done by
them, and for that reason gave very little difficulty in operation.
A basic principle of regenerator design is: the gas passages
should be vertical; the cooling gas should pass downward through
the checkerwork; the gas being heated should pass upward through
the checkerwork. When the gases circulate in this manner they
have a tendency to subdivide themselves between the different
passes proportionally to the local heating and cooling of the brick-
work, with the result that the cooling and heating of the gases will
be practically uniform. A few years ago A. E. Maccoun made a
series of temperature observations on a Cowper hot-blast stove at