In refrigeration terms, what is sub-cooling?

Sub-cooling refers to the process of cooling liquid refrigerant below its condensing temperature. This happens after the refrigerant has condensed into a liquid form but before it enters the expansion device or evaporator. The purpose of sub-cooling is to ensure that the refrigerant is entirely in a liquid state before it undergoes the phase change into a gas in the evaporator, which improves the efficiency of the refrigeration cycle. Sub-cooling helps prevent flash gas from forming before the refrigerant reaches the evaporator, which can lead to inefficiencies and reduced cooling capacity.

In other contexts within refrigeration, adding refrigerant is typically related to recharging a system, and pressurizing refrigerant involves compressing it to change its state or properties, but neither of these processes directly describes sub-cooling. Heating gas refrigerant before entering the compressor is also a different process related to superheating, not sub-cooling. Understanding sub-cooling is essential for technicians to optimize system performance and ensure that components operate efficiently.