Thermal expansion valve

Thermal expansion valve Thermal expansion valves are commonly used in Freon refrigeration systems. Through the function of the temperature sensing mechanism, they automatically change with the temperature change of the refrigerant at the outlet of the evaporator to achieve the purpose of adjusting the amount of refrigerant supply. Most thermal expansion valves set the superheat to 5 ~ 6 ℃ before leaving the factory. The structure of the valve guarantees that when the superheat increases by 2 ℃, the valve will be in the fully open position. When the superheat is about 2 ℃, the expansion valve will Is off. The adjustment spring for controlling the degree of superheat has an adjustment range of 3 to 6 ° C. In general, the higher the superheat set by the thermal expansion valve, the lower the heat absorption capacity of the evaporator, because increasing the superheat takes up a considerable part of the heat transfer surface at the tail of the evaporator, so that the saturated steam is superheated here. It occupies a part of the heat transfer area of ​​the evaporator, so that the area of ​​refrigerant vaporization and heat absorption is relatively reduced, that is to say, the surface of the evaporator is not fully utilized. However, if the degree of superheat is too low, the refrigerant liquid may be brought into the compressor, which may cause an adverse phenomenon of liquid shock. Therefore, the regulation of superheat should be appropriate, not only to ensure that enough refrigerant enters the evaporator, but also to prevent liquid refrigerant from entering the compressor. The thermal expansion valve is mainly composed of a valve body, a temperature sensing bag and a capillary tube. There are two types of thermal expansion valve: internal balance type and external balance type according to the different diaphragm balance methods.

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