Under normal condition, the refrigerant enters the compressor as a:

• A. High pressure superheated vapor and leaves as liquid
• B. Liquid and leaves as high pressure liquid
• C. Low pressure superheated vapor; leaves as high pressure vapor
• D. Low pressure saturated liquid; leaves as high pressure vapor

Answer: (C)

In a vapor-compression refrigeration cycle, the compressor is designed to handle vapor, not liquid. The refrigerant from the evaporator is at low pressure and low temperature, and it is kept in vapor form—often with a bit of superheat added—to ensure there’s no liquid entering the compressor. The compressor then increases the pressure and keeps the refrigerant in the gaseous state, so it leaves as a high‑pressure vapor. This is why the inlet is described as low‑pressure superheated vapor and the outlet as high‑pressure vapor. If liquid were drawn into the compressor, it could cause damaging slugging and improper compression, which is why the other scenarios don’t fit the operation of a typical refrigerant cycle.