Function of expansion valve

Metering device

The metering device controls the flow of liquid refrigerant through the system.

The liquid enters at a high-pressure, high-temperature, sub-cooled state and leaves as a low-pressure, low temperature, expanded liquid state.

Accurator Piston and Thermostatic Expansion Valves are the most widely used metering devices.

Accurator Pistons are widely used because of their low cost and flexibility. The piston can easily be changed to match the capacity of the condensing unit.

The Thermostatic Expansion Valve (TXV) is the most efficient type of metering device.

The TXV automatically adjusts the flow of the liquid refrigerant based on the superheat of the refrigerant leaving the evaporator coil.

As the load on the evaporator increases, the TXV increases the flow of refrigerant. This maintains the proper superheat.

The TXV is efficient throughout a variety of system operating conditions, while the accurator is efficient only under designed conditions.