USCG Exam PracticeRefrigeration cycle and components
A thermostatic expansion valve (TXV) senses the temperature at the evaporator outlet in order to accomplish which of the following?
- A. Hold a constant evaporator pressure regardless of load
- ✓ Maintain a constant superheat at the evaporator outletCorrect
- C. Prevent the condenser from exceeding its rated head pressure
- D. Cycle the compressor on and off in response to box temperature
Why B is correct
The TXV sensing bulb measures the temperature of the leaving vapor and modulates the valve to hold a constant superheat, admitting more refrigerant under high load and less as load falls. Holding constant evaporator pressure is the function of the automatic (constant-pressure) expansion valve, not the TXV.
Cited:NAVEDTRA 14075 §6-4