Question 29Refrigeration & AC - Assistant Engineer

The correct answer is C. The expansion valve designed to maintain a constant evaporator pressure rather than a constant evaporator superheat is the thermostatic expansion valve (TXV). The TXV monitors the pressure at the evaporator outlet and adjusts the refrigerant flow to maintain a constant evaporator pressure, which helps prevent liquid refrigerant from returning to the compressor. The other expansion valve options, A, B, and D, are designed to maintain a constant evaporator superheat, which is the difference between the actual temperature of the refrigerant at the evaporator outlet and the saturation temperature corresponding to the evaporator pressure. These types of expansion valves are not intended to maintain a constant evaporator pressure.