What does the term "subcooling" refer to in a refrigeration system?

Subcooling refers to the process of cooling the refrigerant below its saturation temperature while it remains in the liquid state. This is a critical concept in refrigeration systems because subcooling improves the efficiency of the system by ensuring that all of the refrigerant entering the expansion device is in the liquid phase, thus preventing any vapor from entering and leading to potential inefficiencies in the cooling process.

When refrigerant leaves the condenser, it should be in a saturated liquid state. By applying further cooling, which results in subcooling, the refrigerant becomes denser. This denser liquid can absorb more heat during the evaporation process in the evaporator, leading to better heat transfer and system performance. Additionally, subcooling helps in protecting the compressor by avoiding the entry of vapor, which can cause damage or inadequate cooling operation.

Other terms like the vaporization of surplus refrigerant or injecting additional refrigerant into the system do not apply to the concept of subcooling, as they describe different processes within a refrigeration system and do not relate to the cooling of liquid refrigerant below its saturation temperature.