Expansionsventils

Expansionsventils, commonly known as expansion valves in English, are flow-regulating devices used in vapor-compression refrigeration and air conditioning systems. Their main function is to control the amount of high-pressure liquid refrigerant that enters the evaporator, thereby lowering the refrigerant pressure and enabling it to absorb heat efficiently. By regulating flow, expansion valves help maintain evaporator temperatures and prevent liquid flood-back to the compressor.

The most common types are thermostatic expansion valves (TXVs) and electronic expansion valves (EEVs). A TXV modulates the opening of a precision needle valve based on the temperature or superheat of the refrigerant exiting the evaporator, using a sensing bulb or similar element attached to the evaporator. An electronic expansion valve uses sensors and an electronic actuator to continuously adjust the valve position, offering precise, remote-controlled flow. Capillary tubes are another method of pressure reduction, but they are not valves and provide fixed flow characteristics rather than adjustable control.

Operation centers on maintaining an appropriate evaporator superheat, typically by balancing the refrigerant’s pressure drop with the evaporator load. In TXVs, the sensing bulb's response to evaporator temperature alters the diaphragm and valve opening. EEVs use electronic signals to modulate opening, enabling rapid adaptation to load changes. Proper installation requires correct sensing location, charge, and refrigerant type; mismatches can cause icing, flooding, or unstable cooling.

Applications span residential and commercial air conditioning, refrigeration systems, and heat pumps. Selection depends on desired control accuracy, energy efficiency, system complexity, and maintenance capacity. Common maintenance tasks include checking for leaks, verifying sensor function, and ensuring correct refrigerant charge to maintain stable superheat.