What is the state of the refrigerant when it enters the compressor from the evaporator?

• A. Saturated liquid
• B. Low pressure vapor
• C. Superheated Vapor
• D. High pressure liquid

Answer: (C)

In a vapor-compression refrigeration cycle, the compressor is designed to compress only gas. After the refrigerant passes through the evaporator, it is at low pressure and has absorbed heat, turning into vapor. To protect the compressor from ingested liquid and to ensure smooth compression, the refrigerant is typically brought to a temperature above the saturation temperature for that low pressure, i.e., it is a superheated vapor when it enters the compressor. Saturated liquid would imply liquid present at the compressor inlet, which can cause damage, and a high-pressure liquid contradicts the low-pressure conditions in the evaporator. Hence, the entering state is superheated vapor.