Working principle and function of cold storage expansion valve

Working principle and function of cold storage expansion valve

The expansion valve of a cold storage is a very important equipment accessory in the refrigeration system of a cold storage structure.

The expansion valve restrains the liquid refrigerant at medium temperature and high pressure into low-temperature and low-pressure wet vapor (i.e. mist) through the expansion valve, and then allows the refrigerant to absorb heat in the evaporator of the cold storage equipment to achieve refrigeration effect.

The expansion valve mainly controls the valve flow rate through the change in superheat at the end of the evaporator to prevent underutilization of the evaporator area and knocking of the cylinder.The expansion valve is mainly used in the refrigeration system of a cold storage to reduce the refrigerant from the condensation pressure to the evaporation pressure and proportionally control the refrigerant flow rate.

The operational performance of the entire cold storage refrigeration system will be affected by the quality of the expansion valve.

The expansion valve is mainly used to throttle and control the refrigerant and flow rate in the cold storage system.
   

Throttling effect is to regulate the flow of high-temperature and high-pressure liquid refrigerant through the throttle hole of the expansion valve, and then create conditions for the evaporation of the refrigerant through a low-temperature and low-pressure mist like hydraulic refrigerant.

Control the flow rate of refrigerant in the cold storage system: After the liquid refrigerant enters the evaporator, it evaporates into a gaseous state and absorbs heat, directly reducing the air temperature in the cold storage.

The expansion valve controls the flow of refrigerant in the system to ensure that the refrigerant at the outlet of the evaporator is completely in a gaseous state. If the refrigerant flow rate is too high, there will be liquid refrigerant at the outlet of the evaporator, which may flow into the compressor and cause liquid hammer; If the refrigerant flow rate is too small, it evaporates prematurely, causing refrigeration.

The cold storage expansion valve consists of three main parts: valve body, temperature sensing package, and balance pipe.

The refrigerant injected into the temperature sensing package is in a state of gas-liquid equilibrium saturation, which is not in communication with the refrigerant in the refrigeration system. It is mainly installed and connected to the outlet pipe of the evaporator, in close contact with the pipe to sense the temperature of the superheated steam at the outlet of the evaporator.

Because the refrigerant inside the temperature sensing bag is saturated, it can transfer the pressure of the saturated state to the valve body according to the temperature.

One end of the balance tube is connected to the outlet of the evaporator, at a certain distance from the temperature sensing bulb, and directly connected to the valve body through a capillary tube. The main function is to transfer the actual pressure at the outlet of the evaporator to the valve body. There are two diaphragms inside the expansion valve, which move upwards under pressure, reducing the refrigerant flow through the expansion valve and maintaining balance dynamically.

Shanghai KUB Refrigeration Equipment Co., Ltd.

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