The principle and process of screw chillers are divided into air-cooled and water-cooled types. The screw type chiller is named after its key component - the compressor, which uses a screw type. The unit is powered by a gas refrigerant in the state of the evaporator; After adiabatic compression by the compressor, it becomes a high temperature and high pressure state. The compressed gas refrigerant is cooled and condensed under equal pressure in the condenser, and then transformed into liquid refrigerant after condensation. It is then expanded to low pressure through a throttle valve and becomes a gas-liquid mixture. The liquid refrigerant under low temperature and pressure absorbs the heat of the cooled substance in the evaporator and transforms back into a gaseous refrigerant. The gaseous refrigerant enters the compressor again through the pipeline and starts a new cycle. These are the four processes of the refrigeration cycle and the main working principle of screw chillers.