What do 'direct expansion' systems use to cool the air?

Direct expansion systems use refrigerant to cool the air directly. In this type of cooling system, the refrigerant undergoes a phase change from a liquid to a gas as it absorbs heat from the air inside a building. This process occurs in the evaporator coil, where the warm indoor air passes over the cold coil, leading to heat exchange. As a result, the air is cooled and delivered back into the living space.

This method is efficient because it allows for rapid cooling of the air without the necessity for a secondary medium, like water or steam, to facilitate heat transfer. Furthermore, direct expansion systems are commonly found in various applications, including residential air conditioning, due to their straightforward design and effectiveness in maintaining comfortable indoor temperatures.