The TXV maintains a constant:

The TXV maintains a constant:

• A. Coil temperature
• B. Expansion rate
• C. Superheat
• D. Coil pressure

Answer: (C)

Maintaining a constant superheat is what the thermostatic expansion valve does. Superheat is the difference between the actual vapor temperature leaving the evaporator and the refrigerant’s saturation temperature at the evaporator pressure. The TXV uses a sensing bulb on the suction line to gauge how hot that vapor is. If superheat rises, the bulb’s pressure increases and the valve tightens, reducing refrigerant flow into the evaporator. If superheat falls too low, the bulb pressure drops and the valve opens more, allowing more refrigerant in. This feedback keeps the evaporated refrigerant mostly vapor by the time it leaves the coil, which protects the compressor from liquid slugging and helps match flow to cooling demand. The coil temperature and coil pressure aren’t held constant by the TXV; they vary with load and compressor conditions. The expansion rate isn’t fixed either—the valve adjusts flow to maintain the set superheat.

Maintaining a constant superheat is what the thermostatic expansion valve does. Superheat is the difference between the actual vapor temperature leaving the evaporator and the refrigerant’s saturation temperature at the evaporator pressure. The TXV uses a sensing bulb on the suction line to gauge how hot that vapor is. If superheat rises, the bulb’s pressure increases and the valve tightens, reducing refrigerant flow into the evaporator. If superheat falls too low, the bulb pressure drops and the valve opens more, allowing more refrigerant in. This feedback keeps the evaporated refrigerant mostly vapor by the time it leaves the coil, which protects the compressor from liquid slugging and helps match flow to cooling demand. The coil temperature and coil pressure aren’t held constant by the TXV; they vary with load and compressor conditions. The expansion rate isn’t fixed either—the valve adjusts flow to maintain the set superheat.