During hot gas defrost, which state change occurs in the evaporator?

During hot gas defrost, the primary process that occurs in the evaporator is the melting of frost. This process is essential in cases where frost buildup on evaporator coils can hinder the heat exchange efficiency. By introducing hot gas into the evaporator, the increased temperature causes the frost to melt. This melting transforms the solid frost back into liquid water, which can then be drained away, allowing the evaporator to return to optimal functionality.

The introduction of hot gas elevates the surface temperature of the evaporator, promoting the phase change from solid (frost) directly to liquid (water). It's a crucial aspect of maintaining the system's efficiency and preventing ice accumulation, which can lead to a decrease in performance and operational issues.