The refrigerant vapor must be returned to which state?

In refrigeration systems, the refrigerant vapor must be returned to the liquid state in order to effectively complete the refrigeration cycle. The principle behind refrigeration relies on the continuous transformation and circulation of the refrigerant through various states to absorb and release heat.

During the cycle, the refrigerant evaporates in the evaporator, absorbing heat from the heat source, typically the environment within the refrigerated space. After absorbing heat, the refrigerant turns into a low-pressure vapor. This vapor must be returned to the compressor, where it is pressurized and routed to the condenser. In the condenser, the refrigerant releases its absorbed heat to the surrounding environment and condenses back into a liquid state.

This phase change from vapor to liquid is crucial, as the refrigerant must return to a liquid to be pumped back to the evaporator and continue the cycle of heat absorption and cooling. Returning to a solid or a plasma state would not facilitate the necessary thermodynamic processes in typical refrigeration cycles, as these states do not effectively allow for the absorption and release of heat required for the operation of refrigeration systems.