Thermostatic expansion valve and evaporator (Air conditioning)

Thermostatic expansion valve

Thermostatic expansion valve and evaporator

1 Refrigerant outlet 2 Refrigerant inlet 3 Thermostatic expansion valve 4 Evaporator

The thermostatic expansion valve meters the flow of refrigerant into the evaporator to match the refrigerant flow with the heat load of the air passing through the evaporator matrix.

The thermostatic expansion valve is installed in the heater assembly, in the refrigerant inlet line to the evaporator. Liquid refrigerant flows through the valve to the evaporator. The restriction across the valve reduces the pressure and temperature of the refrigerant and changes it to a fine spray, which improves the evaporation process. Valve opening is controlled by the pressure in a capillary tube containing a temperature sensitive fluid. One end of the capillary tube is connected to a diaphragm housing on the thermostatic expansion valve, the other end of the capillary tube is sealed and attached to the refrigerant outlet line of the evaporator. As the temperature of the refrigerant leaving the evaporator changes, a corresponding change of capillary tube pressure and valve opening are produced. The warmer the refrigerant leaving the evaporator becomes, the greater the volume of refrigerant allowed through the valve.