ARTIFICIAL ICE AND COLD AIR MACHINES.
Historical Sketch--The First Ice Machine--Its Subsequent
Development--Progress in the Use of Machines--The Principles
Involved in their Construction--Diversity of Application--Recent
Discoveries.
The artificial production of cold has engaged attention from remote
ages. The application of spontaneous evaporation in Eastern countries
was the earliest method employed to produce ice.
America has the honor of being the home of the inventors who first
achieved success in making artificial ice by modern methods. Jacob
Perkins, in 1834, and Professor Twinning, of New Haven, Conn., in 1850,
each procured British patents. The former did not procure a patent in
this country, but Professor Twinning secured one in 1853. Two years
later, he had a machine in operation at Cleveland, Ohio, which produced
1,600 pounds of ice in twenty-four hours’ run. This was a favorable
result from a pioneer machine of an estimated capacity of 2,000 pounds
in this time.
Much credit is due these early inventors, who introduced a type
of machine which is now extensively employed, and is known as the
compression system.
In 1851, Dr. John Gorrie, of New Orleans, La., patented a machine
for producing ice, by compressing and expanding atmospheric air.
This machine was also the pioneer of its class. It gave rise to what
are known as air machines, used in England and on the Continent, and
extensively employed for facilitating the transportation of fresh beef
and mutton on the ocean.
In 1848, Ferdinand Carré, of France, contrived an original process for
employing aqua ammonia. In 1865 he patented an ice machine, and at the
French International Exposition, in 1867, daily produced six tons of
ice. This has proved to be a notable invention, the present absorption
system being based upon it and extensively used.
Efforts have been directed to expediting the spontaneous evaporation of
water; a reduction of pressure being effected by a vacuum pump, and the
vapors removed by a suitable absorbing medium. The utilization of cold
obtained by the evaporation of other liquids, more volatile than water,
have received attention.
There have been discovered a number of freezing mixtures, some of which
produce wonderfully low temperatures. The addition of salt to broken
ice is the best known of these; it is commonly employed in making ice
creams and ices, and is of great commercial importance as applied to
refrigerator cars and cold storage houses.
Of all these methods the compression, absorption and air machines, and
the freezing mixture of ice and salt, have entered into commercial
uses in this country. The details of the latter method are referred
to in Chapter VI. Regarding the others, some account of the principal
operations involved, and of the natural phenomena upon which they are
based, will be given.
PRINCIPLES OF ICE MACHINES.--It has been observed of gases, that by
compressing them to a fraction of their original volume, heat was
produced. If the compression was great, most gases were liquified by
it. A few gases were found which would not liquify, and were designated
as permanent. By relieving the pressure, gases will resume their
original bulk, and the heat of compression is gathered up or reabsorbed
by them.
There is, naturally, a constant tendency toward the preservation of
an equilibrium of temperature among the atoms of any body, and also
between different bodies. This exchange is carried on upon a grand
scale, in the economy of nature. Where the difference in degree is
small the exchange is effected slowly, but where it is great the
initial transfers proceed rapidly and with vigor.
By means of efficient insulation we can cut off, in a great measure, a
room, or a part of a room, from the influence of the outer, or general
exchanges of temperature. By this means we are able to bring this
natural law into service, by controlling the exchanges of temperature
of the objects we place in such rooms.
By the union of heat with a fluid, the latter is converted into a
vapor, and the abstraction of heat from a gas converts it into a
liquid. When a fluid or a gas is at the temperature at which a change
in its condition is effected, the continued application or withdrawal
of heat does not increase or diminish this temperature. This heat is
termed latent, or hidden. The temperature at which ebullition takes
place varies greatly with different liquids. Water boils at 212° F.,
while ammonia boils at 32° F. Some substances act as absorbents. Water
will absorb about seven hundred times its bulk of ammonia gas when they
are brought in contact.
In manufacturing low temperatures, by the Compression and Absorption
systems, a liquifiable gas is used as the vehicle by which to
impart cold to, and carry off heat from, the body to be cooled.
Anhydrous-ammonia (ammonia from which all water has been removed) is
usually employed. In the Compression machines, this gas is subjected to
a pressure, averaging one hundred and fifty pounds per square inch, in
a compression cylinder against a piston, which is operated by a steam
engine. The heated gas is carried to a set of condenser coils, which
are cooled by a water bath; here the gas is liquified by the reduction
of temperature and the pressure. By this process it is made to part
with the heat of compression, and its latent heat of vaporization, as
well. The liquid ammonia is collected in a storage tank, and is then
ready for refrigeration duty.
From this point the Compression and Absorption systems are practically
identical. The liquid ammonia is allowed to escape through a valve with
a minute opening, into what are termed the expansion coils. As the
ammonia enters it is freed from about three-fourths of the pressure at
which it has been held, and begins to boil and vaporize. As heat is
necessary to accomplish this, everything within reach of its influence
is placed under tribute. As the gas parted with about five hundred and
seventy heat units per pound at the condenser, its capacity for heat is
now very large.
The expansion coils may be placed in a loft of a cold storage room
in the same position in which ice is placed for this duty. If they
are submerged in a brine solution, the brine is cooled, and may be
circulated in galvanized iron gutters suspended from the ceiling of the
storage rooms.
After circulating through the expansion coils, the gas is drawn out and
forced again into the compression cylinder by a pump which renders the
system a continuous one.
IN MAKING ARTIFICIAL ICE, the expansion tubes may be submerged directly
in the water which is to be frozen; the ice forms in huge cakes on the
tubes, and is sawed into small cakes by a circular saw, when removed.
This is termed the plate system.
In the can plan, a large tank holds the expansion tubes, and, suspended
from its upper side, are numerous iron cans; a brine solution
completely fills the tank, and, being chilled by the tubes, it
gradually freezes the water which has been placed in the cans for this
purpose.
IN THE ABSORPTION SYSTEM, aqua ammonia is placed in a retort containing
a coil of steam pipes. A mixed vapor of water and ammonia is driven
off, until sufficient pressure is developed in the retort to force the
vapor through a small pipe into a condensing tank. Here the gas is
cooled and liquified, and also rectified, or freed from water, making
it anhydrous. The liquid passes into a receiving tank, and is then used
for refrigerator work.
This duty is performed in the same manner as described for the
compression machine. From the expansion coils the gas is returned to a
tank called the absorber, where the water left behind at the condenser
has also been sent; here they are reunited, and then pumped again into
the retort, to begin the round anew.
IN THE AIR MACHINES, this gas is compressed in a cylinder against
a piston, which is driven by a steam engine. The compressed air is
cooled by water jets sprayed in the compression cylinder, and also in a
cooling tank which has a water bath passed over it at the same time.
The condensed moisture is deposited in the cooling tank and in drying
tubes, which are exposed to the spent air which has done refrigeration
duty, and is still cool enough to further lower the temperature of the
compressed air. After being dried, the air is expanded, producing an
intense cold. This air can be circulated in tubes, or used for cooling
brine, as in the methods already mentioned, or the air can be expanded
directly into the storage rooms or ice tanks.
A LARGE PLANT FOR THE STORAGE OF FRUIT is situated at Waldo, Fla.,
and is controlled by the American ice and cold storage company. It is
illustrated in Fig. 88. A perfectly dry, cool atmosphere is maintained,
and a temperature so uniform as to demand only one degree of variation.
The temperature at which the rooms have to be kept varies from 33°
to 45° F., depending on the character of the fruit which is to be
stored. The higher temperatures are preferable, if sufficiently low to
preserve the fruit. Retarding houses for keeping oranges or the more
delicate fruits, can usually be more successfully managed by the use
of refrigerating machinery, as it is not always possible to maintain a
sufficiently even and low temperature by means of ice.
[Illustration: FIG. 88. A FRUIT RETARDING HOUSE IN FLORIDA, WHICH USES
REFRIGERATING MACHINERY.]
THE LATEST INVENTIONS.--All these ice-making and cold air machines
are more or less expensive and complicated. It is natural, therefore,
that inventors should be constantly seeking some plan, idea or method,
for securing a low temperature at less cost for the plant involved.
The expense of the existing systems also prevents their use, except
on a large scale; hence inventors are striving to find not only a
method of producing cold at low cost, but one that can be adapted for
use in houses, offices, stores, shops, cars, etc., on a more or less
limited scale. Several devices for this purpose have already been
patented. Some of them promise good results, though at this writing
none seem to be thoroughly perfected. One of these devices employs a
gas jet, or lamp light, the heat from which, acting on a kettle filled
with chemical compound, produces a low temperature for a small house
refrigerator, while the same principle is claimed to be applicable on a
larger scale.
THE USES OF ARTIFICIAL REFRIGERATION are numerous. For cooling and
ventilating buildings, aiding in some lines of manufactures, and in
chemical works, it has proved its usefulness. In all hot climates it is
extensively employed for making ice. In breweries it is applied very
extensively, and is practically indispensable.
The handling of fresh meat, in the modern method, is directly dependent
upon artificial refrigeration, and in no other direction are its
benefits more marked or widespread. The cattle on our Western plains
have become the daily food of those living at the antipodes. In ten
years, from 1880 to 1891, the imports of fresh beef and mutton into
Great Britain increased from 400 to nearly 3,300,000 carcasses. During
the same period the exports of beef alone from the United States
advanced from 50,500 tons to 101,500 tons.
Not only are meats carried in refrigerator vessels from America and
the antipodes to England, but within a year Australian milk has been
shipped in frozen blocks in such quantities as to be retailed in the
streets of London for four cents per quart. Butter, cheese, eggs,
fruits and other perishable products, are likewise transported enormous
distances by rail or water, without injury to the quality, and at a low
cost for freight.
It is also worthy of mention that refrigeration is now employed by
the engineer, in substructure work in soils abounding in quicksands.
A solid wall of earth is frozen and maintained in such soils, within
which excavating and construction can proceed with ease and safety.
That many other uses for refrigeration will be developed goes without
question. The students and inventors who are engaged on the problems
involved in the production of artificial cold, claim that before many
years all modern houses will be supplied with a refrigerating outfit
in the garret to supply cold air to any of the rooms in summer, by
gravity, as hot air is carried by flues from the furnace in winter.
The universal application of a practical device for this purpose, will
yield a rich reward for the successful inventor.