USCG Exam PracticeRefrigeration cycle and components
A thermostatic expansion valve (TXV) controls refrigerant flow into the evaporator by sensing which parameter at the evaporator outlet?
- A. Suction pressure at the compressor inlet
- ✓ Superheat of the leaving vaporCorrect
- C. Temperature of the condenser cooling water
- D. Liquid level inside the evaporator coil
Why B is correct
The TXV sensing bulb is mounted on the evaporator outlet and measures the temperature of the leaving vapor to determine superheat. The valve modulates to hold a constant superheat, admitting more refrigerant when the load is high and less when it falls, ensuring only vapor reaches the compressor. Liquid level control is the function of a float valve used in flooded evaporators.
Cited:NAVEDTRA 14075 §6-4