Which statement best describes superheating in a refrigeration system?

• A. Superheating occurs when liquid refrigerant is heated after evaporation
• B. Superheating occurs when vapor is heated in the high side
• C. Superheating occurs when refrigerant passes through the condenser
• D. Superheating occurs where no liquid refrigerant is present in the low-side line

Answer: (D)

Superheating is heating the refrigerant vapor beyond its saturation temperature on the low-pressure side, so the suction line carries only vapor. That means by the time the refrigerant reaches the compressor, all liquid has evaporated and the vapor is hotter than its saturated temperature at that pressure. The statement describing no liquid refrigerant in the low-side line captures this condition precisely. Heating liquid after evaporation, heating vapor on the high side, or passing through the condenser describe other parts of the cycle or different states that aren’t superheat.