Refrigeration systems are cyclic processes that employ
refrigerants to absorb heat from one place and move it
to another. Mainly, a refrigeration system consists of a
condenser, an evaporator, a compressor, and an expansion
valve. Fig. 15 shows the schematic of an ammonia
refrigeration cycle which uses three ammonia temperature
levels—18.3, 2.1, and 9.3 1C.