Refrigeration is a thermodynamic cycle. Chillers use refrigeration to extract heat from the process circulation fluid and then ultimately reject it to the atmosphere. This system uses a chemical compound called a refrigerant. There are many types of refrigerants and applications depending on the temperatures required, but they all work on the basic principle of compression and phase-change of the refrigerant from a liquid to a gas and back to a liquid. This process of heating and cooling the refrigerant and changing it from a gas to a liquid and back again is the refrigeration cycle. Changing the physical state of a compound (for example, from gas to liquid) is an extremely efficient means to absorb or expel energy.
The refrigeration cycle in a chiller consists of four key components: compressor, condenser, expansion valve, and evaporator as illustrated below.
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