How is heat transferred from air to the refrigerant in an evaporator?

In an evaporator, heat transfer from air to the refrigerant occurs primarily through the process of conduction. This is the mechanism by which heat is transferred through solid materials when there is a temperature difference.

When air moves over the evaporator coils containing the refrigerant, the temperature of the air is higher than that of the refrigerant initially. As the warmer air comes into contact with the colder surface of the evaporator coil, heat energy is absorbed by the refrigerant from the air. This heat transfer via conduction is crucial because it allows the refrigerant to change phase from liquid to vapor, effectively cooling the air as it happens.

While other mechanisms like convection can play a role in the overall heat transfer process, they are typically more relevant in the movement of air rather than in the direct transfer of heat from air to the refrigerant within the coils. Thus, conduction is the most accurate description of how the heat transfer occurs in this specific scenario.