An air conditioning refrigeration system consists of a compressor, a condenser, an expansion valve and an evaporator. The operation process is as follows: The refrigerant boils at a pressure temperature lower than the temperature of the object or fluid being cooled. The compressor constantly pumps the vapor generated in the evaporator, compresses it to the condensing pressure, and then sends it to the condenser, where it is cooled and condensed into a liquid under the pressure. When the refrigerant is cooled and condensed, the heat released is transferred to the cooling medium (usually the air used by the air conditioner in the room). The condensing temperature corresponding to the condensing pressure must be higher than the temperature of the cooling medium. The condensed liquid enters the evaporator through an expansion valve or other throttling element.

In the whole cycle process, the compressor plays the role of compression and transport of refrigerant vapor and causes the low pressure in the evaporator, the high pressure in the condenser, is the heart of the whole system; The throttle valve has the function of throttling and reducing the pressure of the refrigerant and regulating the refrigerant flow into the evaporator; The evaporator is a device that outputs cold capacity. The refrigerant absorbs the heat of the cooled object in the evaporator, so as to achieve the purpose of producing cold capacity. Condenser is a device that outputs heat. The heat absorbed from the evaporator and the heat converted by the work consumed by the compressor are taken away by the cooling medium in the condenser.