The Salt Lake herald. [volume] (Salt Lake City [Utah]) 1870-1909, 1900-02-27

which were used as cooling agents were
themselves liquefied or sOlidified with
more or less difficulty. II is not neceS-
sary. however. that a substance should
be in the liquid or solid form to pro-
duce cooling effect. a gas may be
made to cool itself.
Heat Changes In Compression and
Expansion.
Everybody who has ever pumped up
a bicycle tire with a hand pump knows
that the compressed air is hot. The
work done upon the air by the pump
ing increases it's store of heat and
raises its temperature. If the air thus
compressed is allowed to escape into
the atmosphere, it has to push away
the outside air, doing work upon it,
and is cooled in the process. Moreover.
II the compressed air has been allowed
to cool to the ordinary atmospheric
temperature before it is released, the
Issuing jet Of expanding air will be
felt 10 be distinctly cold. This is the
action upon which the mOdren re
generative method" is based.
The Regenerative Method.
This method is used on a consider
able scale, chiefly by three experiment.
ers. Ltnde in Germany, Hampsin in
England and Tripler in America. As
Triplers operations seem to be the
most extensive, as well as the most in
teresting TO US for other reasons, his
method viii be described 50 far as it
is publicly known. II is almost absurd
ly simple. There is an air compressor
operated by steam power, coils in
which the compressed air is cooled to
the temperature of the water running
over them, and a .liquefieT," as it is
called from rrbfah Vfpufd al G~a ny,
by the gallon when the plant is in
operation.
The air is compressed three times,
with cooling between; first, to about
sixty pounds above the atmospheric
+ pressure, then TO about 400 pounds, and
/ last to $500 pounds to the square inch.
/ The dust is filtered from the air before
( It enters the compressor and there IS
/ another separation at the highest pres
sure to take out the last traces Of for
/ eign matter. The air at $500 pounds
l pressure and at the temperature Of the
: cooling tanks then passes to the lique-
/ fiers. Of which there are two. Just
/ what the construction of the liquefiers
/ is is not publicly known. Their es-
| sential parts are a long coil of copper
I tube surrounded by a cylinder which
/ is thoroughly wrapped in insulating
/ material. The compressed air passes
l through the copper IuDe ana IS released
| at the end by means of a needle valve.
/ said to be Of some particularly advant-
| ageous design. At thu point it eX-
I pands to about the atmospheric pres
/ sure. and is very greatly cooled in the
/ process. This expanded and cooled air
1 then passes backward over the coils OF
/ pipe and escapes, cooling the COM
/ pressed air within, which, in its turn.
/ expands at the valve and is still
/ further cooled. The process is, there
] fore, progressive and cumulative IN It's
/ cooling effect. and the lowering of tenn
/ peratUre at the release point soon be
! comes so great that part of the air
/ liquefies and collects in the lower end
/ Of the Iiquefiers, from which it can be
drawn off like so much water by open
/ ing a tap.
/ Not the least wonderful thing about II
/ is that this liquid air, at a temperature
/ far below any of which we can have
an adequate conception, Is handled II
/ apparently the most careless fashion
without injury, poured about like
/ water. and transported hundreds Of
: miles in open buckets.
/ NOte-The study of Liquid Air VII
! be concluded next Tuesday.