The evaporator is mainly composed of heating chamber and evaporation chamber. The heating chamber is mainly responsible for providing the evaporation heat to the liquid to make the liquid boil and vaporize. The evaporation chamber is mainly responsible for the complete separation of gas and liquid. Evaporator is one of the four important parts of refrigeration. The low-temperature condensed liquid exchanges heat with the outside air through the evaporator, vaporizes and absorbs heat to achieve the refrigeration effect. Main working steps of evaporator: 1. The liquid refrigerant enters through the feeding port, and the heating steam heats the heating tube bundle inside the heating chamber. Because the heating area of the coarser tube in the middle of the heating chamber is not as large as that of the heating tube bundle, the vaporized refrigerant of the heating tube bundle rises into the evaporation chamber. 2. The liquid refrigerant in the central circulation pipe drops and continues to circulate. (the cross-sectional area of the central circulation pipe is about 40% - 100% of the total cross-sectional area of the heating tube bundle, which also directly affects the efficiency of the evaporator). The application of the evaporator in the fresh air heat exchange unit and fan coil is mainly to provide cold water in the refrigeration process and the heated refrigerant in the heating process. 3. Its application in the ground source heat pump system is opposite to that in the condenser. In the heating process of the ground source heat pump unit, the evaporator belongs to the equipment on the ground source side, which heats the circulating water on the ground source side, and then transfers the hot water to the condenser through the heat exchange of the unit, which discharges the heat in the hot water. 4. In the refrigeration process of the unit, the evaporator belongs to the terminal equipment. The condenser at the ground source side condenses the water at the ground source side and supplies the evaporator with external heat absorption, so as to achieve the effect of external refrigeration.