Air conditioning expansion valve

What is the principle of air conditioning expansion valve?
The electronic expansion valve is a throttling element that can enter the refrigerant flow of the refrigeration device according to a preset procedure. In some situations where the load changes drastically or the operating range is wide, the traditional throttle elements (such as capillary tube, thermal expansion valve, etc.) can no longer meet the requirements of comfort and energy saving. More and more widely used.

Comparison of electronic expansion valve and traditional thermal expansion valve

The thermal expansion valve takes the outlet temperature of the evaporator as a control signal, and converts this signal into the pressure of the steam in the temperature sensing bag through the temperature sensing bag, and recently controls the opening degree of the expansion valve needle to achieve the purpose of feedback adjustment. Disadvantages of thermal expansion method:

1. There is a large lag in the feedback of the signal. The high-temperature gas at the evaporator must first heat the temperature-sensing envelope, which has a large thermal inertia, which causes the temperature-sensing envelope to work inside the temperature-sensing envelope during the reaction. The qualitative heating causes further hysteresis. The lag of signal feedback may cause periodic oscillation of the adjusted parameter.

2.The adjustment range is limited. Because the deformation of the membrane is limited, the change range of the opening degree of the valve needle is small, so the adjustment range of the flow rate is small. When a large flow adjustment range is required, for example, when an inverter compressor is used, the thermal expansion valve cannot meet its requirements.
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3. The adjustment control accuracy is low, the working fluid in the temperature sensing package transmits the pressure to the valve needle through the membrane, and reading and installation will affect and the installation will affect its sensitivity to pressure deformation, so it is difficult to achieve high control Precision.

The application of electronic expansion valve overcomes the above-mentioned shortcomings of thermal expansion valve and provides the conditions for the intelligentization of refrigeration equipment. The electronic expansion valve uses the electrical signals generated by the adjusted parameters to control the voltage and current applied to the expansion valve to achieve the purpose of regulation. However, due to the complicated control system of the electronic expansion valve, the price is relatively high.

Electronic expansion valve can be divided into two categories: electromagnetic type and electric type
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Electromagnetic expansion valve: The adjusted parameters are first converted to voltage and applied to the electronic coil of the expansion valve. Before the solenoid is energized, the valve needle is in the fully open position. After energization, the opening of the valve needle is reduced by the magnetic force. The degree to which the opening degree decreases depends on the control voltage applied to the coil. The higher the voltage, the smaller the opening and the smaller the refrigerant flow through the expansion valve. The electromagnetic electronic magnetic expansion valve has a simple structure and responds quickly to changes in the signal. However, it is necessary to provide the control voltage to the refrigerator when it is working.

Electric type electronic expansion valve: Electric type electronic expansion valve is widely used in stepper motor drive valve needle. Generally can be divided into two types of direct-acting type and deceleration.