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 condensing pressure from rising above a set point
- D. Control the speed of the compressor in response to load changes
Why B is correct
The TXV sensing bulb measures the temperature of vapor leaving the evaporator and modulates the valve to hold a constant superheat. This keeps the evaporator fully utilized while ensuring only superheated vapor — not liquid — reaches the compressor suction. Holding a constant evaporator pressure is the function of an automatic (constant-pressure) expansion valve, not a TXV.
Cited:NAVEDTRA 14075 §6-4