CHAPTER VII.

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.

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.