The air-cooled screw chiller is named air-cooled screw chiller because of its key component-the compressor adopts a screw type. The state of the unit from the evaporator is a gas refrigerant; after adiabatic compression by the compressor, it becomes a high temperature and high pressure state. The compressed gas refrigerant is cooled and condensed at equal pressure in the condenser, and then changes into a liquid refrigerant after condensation, and then expands to a low pressure through a throttle valve and becomes a gas-liquid mixture. Among them, the liquid refrigerant under low temperature and low pressure absorbs the heat of the substance to be cooled in the evaporator and becomes a gaseous refrigerant again. The gaseous refrigerant re-enters the compressor through the pipeline to start a new cycle. These are the four processes of the refrigeration cycle. It is also the main working principle of the screw chiller.