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Full text of "The Flow Of Gases In Furnaces"

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frequently unnecessary for this purpose. Therefore all of those
furnaces which are provided with working openings or doors
operate without " draft.77 This fact will be established.

Consider any reverberatory furnace (Fig. 13) when in operation.
The doors are never hermetically tight to the walls, and a flame
or sting escapes from the interstices at the top of the door. If a

FIG. 13.

lighted torch is held close to the upper part of the door its flame
will incline away from the crack. On the contrary, if the. torch
is held close against the crack at the lower part of the door, it will
be noticed that the flame will be drawn into the furnace. It can
be stated, therefore, that immediately below the roof of the
furnace the pressure of the hot gases inside the furnaces is higher
than the atmospheric pressure at that level; whereas, at the level
corresponding to the lower
part of the furnace the pressure
of the hot gases is less than
the atmospheric pressure, that
is to say, negative with regard
to the pressure at the roof of
the furnace.


If two openings are made
in the walls of this furnace
(Fig. 14), one at the level of
the sole, the other at the level                      FIG. 14.

of the roof, the phenomena
will be the same.    By the lower opening the external air will be