In which phase does the evaporator release heat back into the system?

The correct answer is the gas defrost phase, where the evaporator releases heat back into the system. During this phase, the refrigerant is in a gaseous state and absorbs heat from the surroundings—typically from the environment or the product being cooled. The key aspect of this phase is that it involves introducing warm refrigerant gas back into the evaporator, which helps to melt any frost buildup on evaporator coils, thus releasing stored heat back into the system.

This action effectively facilitates the proper function of the refrigeration cycle by ensuring that the evaporator is not blocked by ice, allowing it to operate efficiently once more. The heat released during this phase is essential for maintaining the efficacy of the refrigerating system, as it helps restore operational conditions following defrost.

The other phases listed do not involve the release of heat in the same way.