ESCO Air Conditioning Practice Exam 2025 – Complete Study Resource

A thermostatic expansion valve (TXV) plays a critical role in managing the flow of refrigerant into the evaporator coil in air conditioning systems. Its primary function is to maintain a specific level of superheat by adjusting the amount of refrigerant flowing through the evaporator in response to varying conditions.

The correct answer, which refers to maintaining constant evaporator superheat, reflects the TXV's design to ensure that the evaporator effectively absorbs heat before the refrigerant returns to the compressor. By maintaining proper superheat levels, the TXV helps prevent liquid refrigerant from returning to the compressor, which could cause damage. It does this by adjusting refrigerant flow based on the temperature of the vapor leaving the evaporator.

In context, maintaining constant evaporator pressure refers to a different mechanism of control typically managed by the compressor and the overall refrigerant system rather than by the TXV itself. Constant refrigerant flow would imply that the system is always allowing the same amount of refrigerant through, which is not how a TXV operates because its flow varies based on demand. Variable refrigerant flow would also imply an adaptive system that changes its output significantly, which isn't a characteristic feature of how thermostatic expansion valves regulate superheat.

Thus, the action