FAA AMT (Aviation Maintenance Technician) Airframe Practice Exam

The function of an expansion valve in a freon cooling system is to act as a metering device and to

1. increase the pressure of the liquid freon

2. reduce the pressure of the liquid freon

3. cool the liquid freon

4. heat the liquid freon

The correct answer is: reduce the pressure of the liquid freon

The correct answer is B - reduce the pressure of the liquid freon. In a freon cooling system, the expansion valve plays a crucial role in regulating the flow of refrigerant into the evaporator. By reducing the pressure of the liquid refrigerant as it passes through, the expansion valve allows the refrigerant to expand and vaporize rapidly. This phase change from liquid to gas is essential for absorbing heat from the surrounding air inside the evaporator coils, thus cooling the air that is eventually circulated throughout the aircraft cabin. Therefore, the primary function of the expansion valve is to reduce the pressure of the liquid freon to enable efficient cooling within the system. Options A, C, and D are incorrect because increasing the pressure of the liquid freon, cooling the liquid freon, or heating the liquid freon are not the functions performed by the expansion valve in a freon cooling system.