What is the definition of subcooling?

Subcooling is defined as the amount of heat removed from a liquid below its condensing point, which is accurate in the context of refrigeration and air conditioning systems. In practical terms, subcooling occurs when a refrigerant in the liquid state is cooled below its saturation temperature at the given pressure. This is crucial in ensuring that the liquid refrigerant entering the expansion device is entirely in its liquid state and not a mixture of liquid and vapor, which helps improve the system's efficiency and performance.

In HVAC systems, achieving proper subcooling ensures that all the liquid refrigerant has effectively absorbed heat from the surrounding environment before it enters the evaporator. This process enhances the system's ability to absorb heat, thereby increasing cooling capacity and efficiency. Subcooling can provide insights into the operating conditions of the system and may indicate the proper amount of refrigerant in the system, contributing to optimal performance.

The other definitions, while related to thermodynamics, do not accurately capture the essence of subcooling in the context of HVAC systems. Hence, the emphasis on cooling a refrigerant liquid below its condensing point fully encapsulates the concept of subcooling.