THE COMPRESSION SYSTEM
FIG. 82.—DIAGRAMMATIC VIEW OF A COMPRESSION MACHINE
One more type of refrigerating machine remains to be described and that is the compression type. This was invented by Jacob Perkins in 1834, but was not developed into a commercial machine until 1850. This machine is the most important of them all. In some respects it is like the absorption process, but in place of adding direct heat a compressing machine is employed. Figure 82 illustrates the system diagrammatically. At A is the compressor which compresses ammonia gas. The gas which is heated by the compressor is then cooled and liquefied in the condenser B. Thence it passes into a brine tank C, where it expands and absorbs heat. From this point it is drawn back into the compressor, thus completing the cycle. In other words, the ammonia must absorb as much heat from the brine as is taken out of it at the condenser.