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What is the function of the electronic expansion valve in the central air conditioning?

May 31,2023

Central air conditioning systems are essential for creating comfortable indoor environments in homes, offices, and other buildings. One of the critical components of central air conditioning is the Electronic Expansion Valve, which helps regulate the flow and temperature of refrigerant entering the evaporator coil. In this article, we will discuss the functions of the electronic expansion valve in more detail.


Function 1: Flow Control

The primary function of the electronic expansion valve is to control the flow of refrigerant into the evaporator coil. The electronic expansion valve does this by sensing the superheat of the refrigerant at the outlet of the evaporator and adjusting the valve opening accordingly. The superheat is the difference between the actual temperature of the refrigerant and its saturation temperature at the current pressure. If the superheat is too high, it means there is not enough refrigerant entering the evaporator, and the electronic expansion valve will open further to allow more refrigerant to enter. Conversely, if the superheat is too low, it means too much refrigerant is entering the evaporator, and the electronic expansion valve will close slightly to reduce refrigerant flow.

Function 2: Superheat and Liquid Level Control

The electronic expansion valve also has a function to control the superheat of the refrigerant leaving the evaporator and the liquid level inside the evaporator. This ensures that the heat transfer area of the evaporator is fully utilized and prevents any damage to the compressor due to overheating during suction or liquid hammer. The superheat control function ensures that the refrigerant exiting the evaporator is at the optimum temperature for efficient heat exchange, while the liquid level control function prevents the compressor from being damaged by liquid slugging.

Function 3: Throttling and Pressure-reducing Effect

Another function of the electronic expansion valve is to throttle the refrigerant and reduce its pressure. The electronic expansion valve can convert the high-temperature, high-pressure refrigerant and liquid into low-temperature, low-pressure refrigerant liquid, producing a small amount of flash gas to reduce pressure. This effect is similar to external heat absorption and helps cool the indoor environment.


In conclusion, the electronic expansion valve is a critical component of central air conditioning systems. Its main functions include controlling the flow of refrigerant into the evaporator coil, regulating the superheat and liquid level to ensure efficient heat exchange, and reducing pressure to facilitate cooling. Proper maintenance of the electronic expansion valve can help extend the lifespan of the central air conditioning system and improve its energy efficiency. If you have any questions about the electronic expansion valve or any other components of your central air conditioning system, feel free to contact us for assistance.

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