Working Principle and function of thermal expansion valve in refrigeration system

Working Principle：

The temperature-sensing bag is filled with refrigerant and placed on the outlet pipe of evaporator. The upper part of the temperature-sensing bag and the diaphragm are connected through a capillary tube to feel the temperature of refrigerant at the outlet of evaporator, the pressure under the diaphragm is felt at the evaporator inlet. If the air conditioning load increases and the hydraulic refrigerant evaporates in the evaporator ahead of time, the refrigerant temperature at the outlet of the evaporator will increase, the pressure on the diaphragm will increase, pushing the valve stem will increase the opening of the expansion valve, when the refrigerant flow into the evaporator increases, the refrigerant capacity increases, and if the air conditioning load decreases, the refrigerant temperature at the outlet of the evaporator decreases, and the valve opening decreases by the same principle, thereby controlling the flow of refrigerant.

Thermal expansion valves have two main functions:

• Throttling: the high-temperature and high-pressure liquid refrigerant is throttled through the throttle hole of the expansion valve and becomes a low-temperature and low-pressure atomized hydraulic refrigerant, creating conditions for refrigerant evaporation.

• Regulating flow: the expansion valve automatically adjusts the flow of refrigerant into the evaporator according to the temperature signal received by the temperature sensing package or the gas tank head to adapt to the changing needs of the refrigeration load.