Main valve technologies in refrigeration systems

The thermal expansion valve controls the injection of liquid refrigerant from the condenser into the evaporator. The expansion valve keeps the superheat at the evaporator outlet at a certain level and prevents liquid refrigerant from leaving the evaporator and entering the compressor. Liquid slugging occurs once liquid refrigerant enters the compressor. This situation must be prevented to avoid damage to the compressor. Pb-temperature sensing bulb pressure Pe-evaporation pressure Ps-spring pressure Pb = Ps+Pe, the diaphragm does not move. When the pressure of the temperature sensing bulb increases, causing Pb > Ps+Pe, the diaphragm moves downward, the valve opens, and more refrigerant flows into the evaporator. When the pressure of the temperature sensing bulb decreases, causing Pb < Ps+Pe, the diaphragm moves upward, the valve closes, and the refrigerant flowing into the evaporator decreases.

Under high pressure conditions, the compressed refrigerant vapor condenses into liquid refrigerant in the condenser. After leaving the condenser, the liquid flows through the reservoir. The reservoir has two main functions. 1. The liquid reservoir compensates for changes in condenser liquid level caused by load changes. When the expansion valve opens/closes, the liquid level in the condenser will change. If there is no "extra" refrigerant in the reservoir, the amount of liquid in front of the expansion valve may be insufficient, causing the expansion valve to not work properly, causing the entire system to become unstable. 2. The liquid reservoir also serves as an additional container to help separate the liquid refrigerant from the refrigerant vapor, ensuring that pure liquid refrigerant leaves the reservoir.

A solenoid valve is a valve that utilizes electromagnetic force. It is an on/off valve that controls the flow of refrigerant based on power on and off. Solenoid valves can be roughly divided into two categories. Direct-acting solenoid valve – When the valve coil is energized, the solenoid valve directly opens/closes the valve port. Servo Solenoid Valve – When powered on or off, the valve opens the pilot port, allowing the main port to gradually open based on the diaphragm/piston pressure differential (depending on whether the valve is NC or NO).

The pressure controller controls and protects the system by preventing the inlet pressure (evaporator pressure) from being too low or the discharge pressure (condenser pressure) from being too high. The pressure controller has two main functions: Protection (or safety) function: Limit the pressure and cut off the power supply when the system pressure is too low or too high. Control functions Compressor cycle, fan cycle and purge

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