After the liquid refrigerant absorbs heat by cooling objects in the evaporator, vaporized into low temperature low pressure steam, steam compressor suction, compressed into high temperature and high pressure discharged into the condenser, the condenser to a cooling medium (water or air) heat, condensing high-pressure liquid, through the throttle valve throttle for low temperature and low pressure refrigerant enter again the evaporator absorbs heat of vaporization, achieve the purpose of refrigeration cycle. In this way, refrigerant in the system through evaporation, compression, condensation, throttling four basic processes to complete a refrigeration cycle.

In the refrigeration system, the evaporator, condenser, compressor and throttle valve are the four essential parts of the refrigeration system, in which the evaporator is the equipment to transport the cooling capacity. The refrigerant absorbs the heat of the cooled object in it to achieve refrigeration. The compressor is the heart that acts as a suction, compressor, and refrigerant vapor. The condenser is a device that emits heat and passes the heat absorbed by the evaporator together with the heat transferred from the compressor's work to the cooling medium. The throttling valve acts as a throttling action to the refrigerant, and simultaneously controls and regulates the amount of refrigerant liquid flowing into the evaporator, and divides the system into two parts, the high pressure side and the low pressure side. The actual refrigeration system, in addition to the above four parts, there are often some auxiliary equipment, such as solenoid valves, dispensers, dryers, heat collector, fusible plug, pressure controller and other components, they are in order to improve the economic operation, reliability and safety setting.