The three main types of chillers are air-cooled chillers, water-cooled chillers, and evaporative chillers. Air-cooled chillers use air to cool the refrigerant, while water-cooled chillers use water to cool the refrigerant. Evaporative chillers use a combination of air and water to cool the refrigerant. Air-cooled chillers are typically used in smaller applications, while water-cooled chillers are used in larger applications. Evaporative chillers are used in applications where water is scarce or expensive. All three types of chillers are used to cool a building or process by transferring heat from the building or process to the refrigerant.