The thermal expansion valve of cold storage equipment is a kind of expansion valve that can automatically adjust the opening degree of the outlet according to the change of the superheat degree of the return gas of the evaporator; it is a temperature regulated throttle. The thermostatic expansion valve can adjust automatically according to the change of the heat load of the evaporator, which is convenient to use, safe and reliable. There are many kinds of thermostatic expansion valve with the same structure, which can be divided into membrane type and bellows type according to the structure of the transmission parts, and internal balance type and external balance type according to the use conditions.

Inner balance membrane thermal expansion valve is often used in small freon refrigeration system, which is mainly composed of valve body, transmission rod, valve core, regulating rod, diaphragm, capillary, temperature sensing package and other components.

The top of the expansion valve is an induction power mechanism, which is composed of an air box, a corrugated film, a capillary tube and a temperature sensing package. The temperature sensing bag is filled with Freon or other boiling point liquid. During installation, fasten the temperature sensing package on the air return pipe at the outlet of the evaporator to sense the temperature change of the air return. The function of capillary is to transfer the pressure change caused by the temperature change in the temperature sensing bag to the corrugated film in the valve top gas box. With the change of the pressure, the corrugated film can deform up and down 2 ~ 3mm. The displacement of the corrugated film pushes the transmission rod which is distributed to the valve needle seat to adjust the opening of the valve port. The lower part of the valve needle seat is an adjusting part, which is composed of a spring, a spring seat and an adjusting rod. The function of the regulating mechanism is to adjust the opening superheat of the expansion valve by adjusting the spring force.

External balance membrane thermal expansion valve
      The structure of the external balance type thermal expansion valve is basically the same as that of the internal balance type. The main difference is that the valve body of the external balance type thermal expansion valve has a balance pipe connected with the outlet of the evaporator, so the refrigerant pressure acting on the bottom of the corrugated film is not the refrigerant pressure at the inlet of the evaporator, but the refrigerant pressure at the outlet of the evaporator connected through the balance pipe. External balance type thermal expansion valve is mainly used for throttling liquid supply of evaporator with large flow resistance.