What is the function of a thermal expansion valve (TXV) in a refrigeration cycle?

The function of a thermal expansion valve (TXV) in a refrigeration cycle is to regulate the flow of refrigerant into the evaporator coil. This regulation is critical because the TXV allows the system to maintain optimal temperatures and pressures within the evaporator, ensuring efficient heat exchange. The TXV adjusts the flow of refrigerant based on the temperature and pressure of the refrigerant exiting the evaporator, which helps in maximizing the cooling effect while preventing issues such as flooding or starvation of the evaporator.

Through this control mechanism, the TXV also supports system efficiency by maintaining a proper superheat level, which is the temperature of the refrigerant vapor above its boiling point at a given pressure. Managing this superheat is vital to protect the compressor from potential damage caused by liquid refrigerant entering it.

The other choices do not describe the function of a TXV accurately; increasing the pressure of the refrigerant is managed by the compressor, controlling discharge temperature is related to the compressor and system design, and converting refrigerant from gas to liquid occurs in the condenser, not through a TXV.