REFRIGERATION. 794 REFRIGERATION. The size of the refrigerating plant varies, of course, «ith the size of the store which it has to keep cold. The refrigerating processes most useJ for cooling stores are the cold-air, the compres- sion, and the absorption processes. Wlien the cold- air j)rocess is employed the air is as a rule admit- ted to the store, and after it has done its duty is conducted back to the compressor for recomjires- siou. Wlu-n compression or absorption systems are used the refrigeration is eflected in one of three ways: (1) By cooling a non-congealable brine and then pumping it through a system of pipes in the store; (2) bj' causing a current of air generated by means of a fan or otherwise to impinge against surfaces reduced to a low tem- ])erature by the expansion of the refrigerating agent itself; (3) by expanding the gas direct through pipes placed in the chambers. The agent employed in the brine cu'Ciilaliny system consists of a solution of chloride of sodium (common salt), chloride of calcium, or chloride of mag- nesium, or any other suitable solution capable of standing very low temperatures ithout congeal- ing. To extract the heat from the brine the method most commonly employed consists in pass- ing it through a tank fitted with suitable coils of pi])es through which the chilled liquefied ether, carbonic acid, ammonia, or other agent expands and forms gas. The cooled brine from this tank is then pumped through a system of circulating pi])es in the refrigerating chamber. In the direct exj/finsioii Sjistciji the pipes in which the ether, carbonic acid, or ammonia expands and makes gas arc located directly in the refrigerating chamber. In the cold-air bifist si/stcm. the expansion coils are placed in .a separate chamber and the cold air from that chamber is blown by fans into the re- frigerating chamber, sometimes being washed by passing tlirough a shower of cold brine and then dried by passing through a mass of calcium chlo- ride or other hygroscopic material. The construction of rcfrirjcrating chambers varies with their purpose and the arrangement of piping adopted, but they are always tightly closed rooms with thick walls carefully insulated to pre- vent escape of cold and entrance of heat. Speak- ing generally, cold-storage rooms or chambers are maintained at a temperature of about 34° F., chilling rooms at about 30" F., and freezing rooms "at anything from 0° F. to 10° F. The proper methods of storing and the temperatures for the cold storage of various articles, as meats, fish, butter, cheese, milk, eggs, fruits, and vegeta- bles, are intricate problems, which different au- thorities solve in different ways; their full dis- cussion can be attempted only in special treatises. IMarixe Refrioeration. Marine refrigeration embraces generally the operation of cold stores and ice-making plants on shipboard. These are merely modifications of the plants used on land to adapt tlicm to the special conditions which pre- vail on .shipboard. These conditions are chiefly limited space and the necessity of using a refrig- erating ag<'nt which is not deleterious to persons or property. To meet the last condition, cold-air and carbonic-acid machines offer advantages which have caused them to be very largely adopted. Fig. 4 shows a car.bonic-acid compression ma- chine designed for use on shipboard. The main point to be noted is the compactness of the ar- rangement. Fig. 5 is a plan of a cnld-storage room on a large passenger steamer. The following is a description of the refrigerating rooms on the steamers Campania and Lucania which are fitted to carry cargoes of meat: The cargo holds of the steamships Campania and Luciania are refriger- ated with machines of the Kilbourn type. The meat-carrving chambers in each of these vessels Fig. 4. MARI.NE TYPE OF CARBONlC-AClD COMPI{Ee.'*ION BEFBIGEHATIXG MACHINE. consist of tluee chambers situated forward on the orlop or lower deck, and having a total cai)acity of 20,000 cubic feet, which renders them able to carry 2700 quarters of beef. The chambers are very carefully insulated, the walls consisting, first, of a double thickness of tongued and grooved boards having a layer of waterproof paper between them ; next, a two-inch ■Mana[incf ffoom "••Ice makirtof Tcmli Fig. ABEANGEMENT OF HEFBIGERATING PLANT ON LARGE PASSENGER BTKAMER. layer of good quality hair felt and another double thickness of tongued and grooved boards, with a similar layer of paper between them; and finally an inch air space, between the latter and the inner or iron deck, the whole being well varnished. The brine-cooling pipes, which are of hea-j' two- inch galvanized tube with malleable cast return bends, are placed on the ceiling between the deck- beams, thus economizing head room, and the rails for the meat-hooks are IVs-inch galvanized round iron, firmh' clipped to the beams supporting the decks. The meat-hooks which are placed upon the latter, for carrying the quarters of beef, are of steel galvanized. Thermometer tiibes from the upper deck are provided to each chamber, so that the temperature may be ascertained in any part of the chamber when desired. Ice-Making. One of the most important appli- cations of refrigeration is the manufacture of artificial iee. There are several methods of ice
