The evaporator cools and dehumidifies the air before the air enters the vehicle. High-pressure liquid refrigerant flows through the orifice tube into the low-pressure area of the evaporator. The heat in the air passing through the evaporator core is lost to the cooler surface of the core, thereby cooling the air. When the process of heat loss from the air to the evaporator core surface takes place, any moisture in the air condenses on the outside surface of the evaporator core. This condensed moisture drains as water.