FAA AMT Airframe Test 2026 – 400 Free Practice Questions to Pass the Exam

In a vapor cycle cooling system, the refrigerant enters the evaporator as a low-pressure liquid. This is because, after passing through the expansion valve, the high-pressure liquid expands and evaporates in the evaporator due to the low pressure and temperature conditions present there. As the refrigerant absorbs heat from the cabin air passing over the evaporator coils, it undergoes a phase change from liquid to vapor, which is essential for the cooling process to occur efficiently.

Regarding the other options:

A. High-pressure liquid - This is incorrect because the refrigerant needs to be at a lower pressure to evaporate and absorb heat in the evaporator.

B. High-pressure vapor - This is incorrect as the refrigerant should be in a liquid state when entering the evaporator, not as a vapor.

C. Low-pressure vapor - This is also incorrect because the refrigerant is in a liquid state as it enters the evaporator, ready to absorb heat and evaporate inside the coils.