What is the purpose of sub-cooling the refrigerant before it leaves the condenser?

• A. To increase its pressure
• B. To prepare it for expansion
• C. To reduce its temperature below the saturation point
• D. To enhance its vaporization ability

Answer: (C)

Sub-cooling the refrigerant before it leaves the condenser serves the important function of reducing its temperature below the saturation point. This process ensures that the refrigerant is in a fully liquid state and helps to improve the efficiency of the refrigeration cycle. When the refrigerant is sub-cooled, it has a lower temperature than the saturation temperature at its given pressure, which helps prevent any remaining vapor from entering the expansion device. This is crucial because any vapor present can lead to reduced efficiency and potential damage to the compressor.

Additionally, having a completely liquid refrigerant entering the expansion device ensures that the phase change occurs effectively, enhancing the system's overall performance. Sub-cooling also adds a margin of safety to the system, minimizing the risk of compressor damage due to liquid carryover, as the compressor is designed to handle only vapor. Thus, sub-cooling plays a vital role in ensuring the effective operation of the refrigeration system.