Subcooling is a term used in refrigeration systems and refers to a liquid existing at a temperature below its normal boiling point. It is the amount of heat removed from a liquid below its condensing point. Subcooling is an important stage in the refrigeration cycle, allowing technicians to ensure that the quality of the refrigerant is the desired one before it reaches the next step in the cycle. Subcooling can take place in heat exchangers and outside them. It is also used indirectly on the superheating process, and both processes can be coupled using an internal heat exchanger. Subcooling serves itself from the superheating and vice versa, allowing heat to flow from the refrigerant at a higher pressure (liquid) to the one with lower pressure (gas). The most commonly known subcooling is the condenser subcooling, which is usually known as the total temperature drop that takes place inside the condenser, immediately after the fluid has totally condensed, until it leaves the condensing unit. Mechanical subcooling is the temperature reduced by any artificial process that is deliberately placed to create subcooling.

In summary, subcooling is a crucial process in refrigeration systems that ensures the quality of the refrigerant before it reaches the next step in the cycle. It is the amount of heat removed from a liquid below its condensing point and can take place in heat exchangers and outside them. Subcooling is also used indirectly on the superheating process, and both processes can be coupled using an internal heat exchanger.