The compressor is the heart of the AC system and also the costliest. It increases the pressure and temperature of the refrigerant gas coming from the evaporator coils by compressing it.
Compressors come in various types.
The most widely used is the simple reciprocating type with a cylinder and piston arrangement. For capacities more than 120 TR, centrifugal compressors are used. The more recent additions have been the rotary and screw compressors that are more efficient than the others. The condenser liquefies the refrigerant gas by a heat exchange process. The capillary tube or the expansion valve pressurizes the liquid refrigerant and meters its flow to the evaporator.