The thermostatic expansion valve (TXV) is a METERING device, which is designed to regulate the rate at which liquid refrigerant flows into the evaporator. This controlled flow is necessary to maximize the efficiency of the evaporator while preventing excess liquid refrigerant from returning to the compressor (floodback). The expansion valve is an essential component in almost every refrigeration cycle and the thermostatic expansion valve is the most commonly used within HVAC systems.
One of the design features of the TXV is to separate the high pressure and low-pressure sides of an air conditioning system. Liquid refrigerant enters the valve under high pressure via the system’s liquid line, but its pressure is reduced when the TXV limits the amount of this liquid refrigerant entering the evaporator coil.