USCG Exam PracticeRefrigeration cycle and components
The thermostatic expansion valve (TXV) on a marine refrigeration plant modulates 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. Liquid level inside the evaporator coil
- D. Discharge pressure at the compressor outlet
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 the evaporator is fully used while preventing liquid from reaching the compressor.
Cited:NAVEDTRA 14075 §6-4