A complete explanation of the working principle of the refrigeration machine expansion valve: helping to optimize the performance of the refrigeration system
In the refrigeration system, the expansion valve of the chiller plays a vital role. It is like a “traffic policeman” in the refrigeration cycle, accurately controlling the flow and pressure of the refrigerant, directly affecting the performance and efficiency of the entire refrigeration system. A deep understanding of the working principle of the chiller expansion valve has far-reaching significance for optimizing the refrigeration system, improving the refrigeration effect and reducing energy consumption.
Basic structure of the chiller expansion valve
The chiller expansion valve is usually composed of main components such as valve body, temperature sensing package, capillary, valve needle, spring, etc. The valve body is the outer shell of the entire expansion valve, and there is a flow channel inside, in which the refrigerant flows. The temperature sensing package is installed on the pipe at the outlet of the evaporator, and it is connected to the top of the diaphragm of the expansion valve through a capillary. The valve needle is connected to the diaphragm and controls the opening of the valve under the drive of the diaphragm. The spring provides a reverse force, which is balanced with the pressure above the diaphragm, and jointly determines the opening degree of the valve.
Detailed explanation of the working principle
The decompression process of the refrigerant
When the high-temperature and high-pressure refrigerant liquid flows out of the condenser, it first enters the chiller expansion valve. One of the main functions of the expansion valve is to reduce the pressure of the refrigerant. Due to the sudden narrowing of the flow channel inside the expansion valve, the refrigerant will encounter greater resistance when passing through, and according to the principles of fluid mechanics, the pressure will drop sharply. This causes the refrigerant to change from a high-pressure liquid to a low-pressure liquid, creating conditions for the subsequent evaporation process in the evaporator.
Flow control mechanism
The temperature sensing package is a key component for the expansion valve of the refrigeration machine to achieve flow control. The temperature sensing package is filled with the same medium as the system refrigerant. When the refrigerant temperature at the outlet of the evaporator changes, the medium temperature in the temperature sensing package also changes. The change in temperature will cause the pressure of the medium in the temperature sensing package to change. For example, when the outlet temperature of the evaporator increases, the medium in the temperature sensing package expands, the pressure increases, and is transmitted to the top of the diaphragm through the capillary tube, causing the diaphragm to deform downward, pushing the valve needle to move downward, the valve opening increases, and more refrigerant can flow into the evaporator; conversely, when the outlet temperature of the evaporator decreases, the medium in the temperature sensing package shrinks, the pressure decreases, and under the action of the spring force, the diaphragm deforms upward, the valve needle moves upward, the valve opening decreases, and the refrigerant flow into the evaporator decreases. Through this dynamic adjustment mechanism, the expansion valve of the chiller can accurately control the flow of the refrigerant according to the change of the heat load of the evaporator, ensure that the refrigerant in the evaporator can fully evaporate, and improve the refrigeration efficiency.
Working characteristics of different types of chiller expansion valves
Thermal expansion valve
Thermal expansion valve is the most widely used type of chiller expansion valve. Its advantage is that it can automatically adjust the refrigerant flow according to the superheat at the outlet of the evaporator, and has a strong ability to adapt to load changes. During the operation of the refrigeration system, when the heat load of the evaporator increases, the superheat of the refrigerant at the outlet of the evaporator will increase, and the thermal expansion valve will increase the valve opening accordingly, increase the refrigerant flow to meet the refrigeration demand; when the heat load decreases, the superheat decreases, and the valve opening also decreases. This automatic adjustment feature enables the thermal expansion valve to better maintain the stable operation of the refrigeration system, and has been widely used in various refrigeration equipment.
Electronic expansion valve
With the development of science and technology, electronic expansion valves have gradually emerged in the field of refrigeration. Electronic expansion valves control the valve opening through electronic controllers. It can accurately adjust the refrigerant flow rate according to multiple parameters of the refrigeration system, such as the evaporator inlet and outlet temperatures, the compressor suction pressure, etc. Compared with the thermal expansion valve, the electronic expansion valve has higher adjustment accuracy and faster response speed. It can adapt to changes in the operating conditions of the refrigeration system more quickly and achieve more efficient refrigeration control. For example, in some application scenarios with high requirements for refrigeration accuracy, such as precision air conditioning, cold storage, etc., the electronic expansion valve can better play its advantages and provide more stable and efficient operation guarantee for the refrigeration system.
