HEFBIGERATION. 791 REFRIGERATION. ■to the compression process, however much they may diflfer in more or less important details, must consist of these main parts, as shown by the diagram Fig. 1 : ( 1 ) A compressor. A, in which the gas is compressed in some convenient and suitable manner; (2) a condensing side or condenser. B, in which the gas circulates through ■vrater-cooled pipes or coils or their equivalent and liquefaction takes place; (3) an expansion side, C. consisting of pipes or coils or other space wherein the gas can reexpand and perform its work of cooling or refrigerating by abstracting heat from the surrounding objects. In Fig. 1 D is a regulating valve, E is the low-pressure gauge, and F the high-pressure gauge. Only those liquids are capable of being used as refrigerating agents which possess vapors capa- ble of being liquefied under pressure at ordinary temperatures. There are several such liquids, but those most used in refrigeration are anhydrous Wafer Supply Oil Cooler extracting the heat from the gas during com- pression by the simple device of injecting into the compressor at each stroke a certain quantity of a special quality oil. Fig. 2 shows diagram- mat ically a De j!l Vergne refrigerating plant with all machinery in place. It consists of two sets of apparatus, one set being that required to compress, condense, and expand the ammonia gas and the other set being that required for hand- ling the scaling and cooling otl. Following first the path taken by the ammonia in order to pro- duce the refrigerating effect, there is the compres- sion cylinder, which is of the double-acting type, and the steam-engine cylinder, which is horizon- tal. The pipe through which the gas is drawn or sucked from the evaporating coils into the compression cylinder is also shown. The gas is discharged by the action of the compressor through the pipe into the pressure tank. From the pressure tank the gas, which still retains the Exhaust Steam Fig. 2. diagram sectio.v of a eefeigeuatiso plant on ammosia compbessios ctctem. I ammonia, ether, methyl chloride, sulphurous acid, and carbonic acid. The first compression refrigerating machine was invented by Jacob Perkins in 1834. Subsequent improvements were made bv Professor Twining in 1850, by James Harrison in 1856. bv Charles Tcllier a few years later, and bv Van der Weyde. Pictet,- and Wmd- hausen at still later dates. The modem refrig- erating agent which is most used is anhydrous ammoSia, which boils at 40= F. There are numerous ammonia refrigerating machines in use, but they differ from each other only m de- tails the general construction being the same m all As an illustration of the general compres- sion process and of the machinery and apparatus emploved in conducting it a refrigerating plant on the De La Vergne ammonia compression sys- tem may be described. Its characteristic feature consists in the patented system for preven ing the occurrence of any leakage of gas takmg pjace past the stuffing bos, piston, and valves, and of heat due to compression, passes upward through the pii)e into the bottom or lower pipe of the condenser, wherein by the cooling action of the cold water running "over the pipes the heated cas is first cooled and then liquefied. The am- monia in this liquid condition is then led by the small liquid pipes through the liquid header into the storage tank, whence it flows through into the lower part of the separator, which is constantlv maintained at least three-quarters full Bv reason of the pressure to which it is now subjected, the liquid ammonia is forced to the expansion cock or valve, through which it is injected into the evaporating or expansion coil which is situated in the room or chamber to be rcfrigerate<l or cooled. The ammonia gas resulting from the expansion and evaporation of the liquid ammonia in the evaporating or expansion coil, having absorbed or taken up the heat from the surrounding atmos- phere passes away back into the compression
