What is an Automotive Air Conditioning Expansion Valve?

[KennedyRose]

An automotive air conditioning expansion valve is a device that controls the flow of refrigerant into the evaporator by regulating the superheat of the gaseous refrigerant at the evaporator outlet. In specialized air conditioning systems, due to the branching of the evaporator and the use of a showerhead-type liquid distributor, the pressure drop is relatively large, resulting in varying temperatures at the evaporator's inlet and outlet. The expansion valve is generally composed of three main parts: the valve body, the temperature sensing bulb, and the balance tube. Its primary function is to throttle and reduce pressure, transforming the medium-temperature, high-pressure liquid refrigerant into a low-temperature, low-pressure wet vapor before it enters the evaporator. The refrigerant then absorbs heat in the evaporator to achieve the cooling effect. Automotive air conditioning expansion valves are classified into two types: internally balanced and externally balanced thermal expansion valves.