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The Working Principle of Electronic Expansion Valve in Constant Temperature and Humidity Test Chamber

As an electronic control element, the electronic expansion valve located in the constant temperature and humidity test chamber adjustment system has high accuracy, fast action, accurate action, and obvious energy-saving effect, which can realize the optimal control of the system and has a wide range of applications in environmental test equipment. But do you know how it works? Do you know the role of its design? Next, let's analyze the working principle and design function of the constant temperature and humidity test chamber's electronic expansion valve.


The driving method of the electronic expansion valve is that after the controller of constant temperature and humidity test chamber calculating the parameters collected by the sensor, it sends an adjustment command to the drive board, and the drive board outputs electrical signals to the electronic expansion valve to drive the action of it. The electronic expansion valve takes only a few seconds from fully closed to fully open, with fast response and action speed, and there is no excessive static heating. Moreover, its open and closed state and speed can be set manually, which can adjust and control the amount of liquid refrigerant entering the evaporator well. For example, when doing a sixty-degree single temperature test, you can adjust the electronic expansion valve to reduce its opening to a suitable value. Simultaneously, the cooling capacity is relatively small, and the heating capacity balanced with it can also be reduced, so as to reduce energy consumption in both cooling and heating in order to achieve energy saving effect.


Japan began to study it in the late 1970s. At that time, it relied on the application of different voltages (0~12V) to heat the bimetallic strip, which caused the bimetallic strip to expand differently and drive the valve needle to rise and fall. It has significant drawbacks and has not been used much later. In addition to Japan, other countries also carried out research and development of electronic expansion valves in the 1980s, which was mainly for electromagnetic and electric (stepper motor drive) electronic expansion valves.


The expansion valve, also called the throttle valve, is the main component of the refrigeration system of the constant temperature and humidity test chamber, which is installed at the entrance of the evaporator and is the dividing point between the high pressure and the low pressure of the refrigeration system. Its function is to throttle and decompress the high-pressure liquid refrigerant from the receiver dryer, adjust and control the amount of liquid refrigerant entering the evaporator to adapt it to the changes of the refrigeration load, and at the same time to prevent the compressor from the fluid hammer (that is, the unevaporated liquid refrigerant is compressed after entering the compressor, which can easily cause damage to the compressor valve) and abnormal overheating of the evaporator outlet vapor.


The above is the working principle and design function of the electronic expansion valve of the constant temperature and humidity test chamber that we share with you.

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