Evaporators are heat exchangers that transfer heat from the process fluid into the refrigerant causing a phase change, evaporation. In an evaporator, the refrigerant enters as a low-pressure liquid/vapor mixture and exits as a low-pressure gas. The change of state from liquid to gas occurs at a constant temperature and absorbs energy. A chiller’s evaporator achieves superheated refrigerant vapor. Superheat is when all the liquid refrigerant has evaporated, and the gas temperature increases above its saturation temperature. The process fluid enters as a hot liquid and exits at a lower temperature after transferring energy to the refrigerant.
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