In hot gas defrosting, which phase change in the refrigerant is primarily responsible for removing frost?

In hot gas defrosting, the primary phase change in the refrigerant that is responsible for removing frost is actually evaporation. During the defrosting process, the refrigerant is heated and then becomes a hot gas. This hot gas is circulated through the evaporator coil, where it absorbs heat from the surrounding area, effectively melting the frost or ice that has accumulated.

As the frost or ice melts due to heat being transferred from the hot gas into the frost, it then turns into water, allowing it to drip away. This process is crucial for maintaining the efficiency and functionality of refrigeration systems, especially under conditions that lead to frost formation. The melting of the frost is a direct result of the heat transfer from the evaporating refrigerant.

Heat absorption through evaporation of refrigerant is essential for this process. In contrast, condensation refers to the transition from gas to liquid, which would not contribute to the defrosting effect, while freezing and melting relate more to the state changes of the frost itself rather than the refrigerant's role in providing heat. Thus, hot gas defrosting leverages the evaporation of the refrigerant to facilitate the removal of frost effectively.