PARKER Thermostatic Expansion Valves

Thermostatic Expansion Valves

Thermostatic expansion valves, often abbreviated as TXVs, TEVs or TX valves reduce refrigerant pressure from the condenser pressure to the evaporator pressure. These valves keep the evaporator active as they increase the flow of refrigerant at high capacity loads and reduce the flow at low capacity loads. Thermal expansion valves provide complete evaporation of liquid refrigerant in the evaporator, thus eliminating liquid slugging. Thermal expansion valves can tolerate variation in refrigerant charge, as they adapt the refrigerant flow for matching the heat load. These valves minimise coil starving & flood back problems by controlling accuracy.

Uses

Parker Thermostatic expansion valves are used for regulating the flow of liquid refrigerant into an evaporator in aerospace, fluid & gas handling, hydraulic, filtration, sealing, shielding and process control applications.

Working Mechanism

The high-pressure liquid refrigerant is held back from the condenser by the valve. The valve regulates how much refrigerant can enter the evaporator. The valve decreases the pressure, allowing the refrigerant to boil at decreased temperatures. As the refrigerant is exposed to more thermal energy while passing through the evaporator, it undergoes a complete phase change and becomes a saturated vapour while reaching the end of the evaporator coil. During this change, there is almost no temperature change due to latent heat. Instead, there is an increase in entropy and enthalpy. The refrigerant continues picking up thermal energy and after the phase change, it begins increasing the temperature, thus superheating the refrigerant vapour. This temperature is monitored by the sensing bulb of the expansion valve to control the refrigerant in the main body of the valve.