In what form does refrigerant enter the evaporator?

The correct answer is that the refrigerant enters the evaporator as a liquid. This phase change is crucial for the refrigeration cycle to function effectively. When the refrigerant enters the evaporator in liquid form, it is able to absorb heat from the surrounding environment, typically from the space that needs to be cooled.

As the liquid refrigerant absorbs heat, it undergoes a phase change and evaporates into a vapor, which is later compressed and cycled back through the system. This process of heat absorption and phase change is vital because it is what allows the system to cool down the area being conditioned. Understanding this phase transition is essential for operating and maintaining refrigeration systems efficiently.

Other forms such as gas, vapor, or solid are not suitable for entering the evaporator in a standard refrigeration cycle under normal operating conditions, as they would not facilitate the necessary heat exchange process that keeps cooling systems effective.