For further reports of tests, see Trans. A. S. M. E., vol. xi, for trials of a De in Vergne refrigerating plant.
Ammonia Condensers, which perform the work of condensing and liquefying the ammonia as it is discharged from the compressors. have the coils in which the condensation of the gas takes place immersed in a deep tank of water, and the heated gas enters the coils at the top of the tank, while the condensing water enters the tank at the bottom and overflows at the top. In this forth, which is known as the submerged system, the hot gas front the machine first meets the warm water at the top of the tank, and as it passes toward the bottom of the coils gradually gives off its heat to the surrounding water, until it reaches the cool water at the bottom, where it becomes liquefied, and passes into the receiver. In an air-condenser the coils are not submerged, but water is trickled over the pipes, and both air and water absorb the heat of compression, and thus serve to condense and liquefy the gas. Efforts have been made in the direction of concentrating all the air in a high condensing pressure system in one place, where it may be discharged through a valve, and a fair measure of success has been attained. This is of great value, as the presence of air trapped at various parts of the appa ratus has frequently required the evacuation of the whole system.
A cling Cmnprpssur is shown at Fig. 2. It is self-contained and horizontal, with the steam-engine that furnishes power for iL on the same bed-frame, the piston-rods of both gas-cylinder and steam-cylinder being in a direct line front center to center. The wrists con necting the driving-rods with the cross-head and with the wrist-pins on the outside of the fly wheels. avoid the wear and tear inevitable from the ordinary crank and fly-wheel system. By a special arrangement, consisting of a chamber formed in the at and a pipe or pipes leading from it to the suction side of the gas-cylinder, the pressure on dm Mulling-box around the piston-rod, as it collies out of the gns-cylinder, is equalized with the back pressure from the expansion-coils, which pressure usually ranges from 15 to 25 lbs. to the sq. it). Another device dispenses with the use of water as a means of cooling the piston-rod, this being done by a constant flow of oil through an oil-ehamber built on the gland of the stuffing-box itself. A third improvement made by the inventor (John Ring. of St. Louis) of the above machine, and embodied in his ice-making system, is based upon the fact that the ammonia goes through the expansion-coils, in actual work, so rapidly that at the outlet it still has in it the capacity of further absorption of heat.
After leaving the coils the gaseous ammonia goes to one or more receivers, where a further compression is produced by simply arranging the outlet-pipes so that their area will be slightly less than that of the inlet-pipes. When
expanded into other coils beyond the receiver, the gas can be utilized to cool the distilled water in ice-making, and additional rooms in refrigeration.
Gold Storage. — For storing perishable goods at temperatures above or below the freezing-point, and making ice in connection with the same, a useful combination is formed in the plant produced by an English Cold Storage Co., and called " Hill's Refrigerating Apparatus and Dry-Cold Air-Chamber." The apparatus consists of : (a) An ammonia-boiler, separator, and condenser with connec tions, for producing the cold. (b) A refrigerator or cold chamber, with non-conducting walls, the roof of which is formed by a tank containing a non-congealable liquid which can be reduced to any required temperature down to 70' F. below the freezing-point. The working involves no risk. A slow-combustion stove is required containing a coil for the rapid genera tion of steam, which is used to convey heat to the ammonia-boiler. Steam can be raised by the use of coke, gas, spirit, or oil; or, if a steam-boiler already exists, then steam may, of course, be taken from it.
The cold is produced as follows: (a) By the distillation of ammonia-gas from water in which it is held in solution. (b) By the conversion of dehydrated gas by automatic pressure into liquid anhydrous ammonia. (c) By the automatic evaporation (under control) of the liquid anhydrous ammonia. (d) By reabsorption of the gaseous ammonia in the water in which it was originally held in solution.
By the third stage of the operation (c) the latent heat is extracted from the bulk of the liquid anhydrous ammonia and the sensible heat from the cold-storage bath. Intense cold is thus produced in and stored up by the said bath to the desired degree of temperature (either above or below freezing). The tank containing the cold-bath forms the ceiling of the cold chamber. and, being cf the same temperature as the bath, abstracts the heat from the air in the chamber, and as the coldest air falls to the bottom of the room, the warmer air, rising to fill its place, is in its turn cooled, and, falling, a constant circulation is automatically kept up ; at the same time, the air is dried by freezing out the moisture ordinarily contained in it—a feature which presents advantages when dealing with the storage of perishable articles of food. The cold-bath liquor and ammonia, the only chemicals used in the process, suffer prac tically no waste, and neither of them come in contact with the contents of the cold-chamber. Any degree of dry cold can be obtained ; and a reserve of cold can be stored up and given out automatically as required.
A valuable paper and discussion on refrigerating and iee-making machinery and appliances appear in _time.
Inst. of Mech. Engrs.. May. 188G.