Cooling towers are heat removal devices used to transfer process waste heat to theatmosphere. Cooling towers may either use the evaporation of water to remove process heat and cool the working fluid to near the wet-bulb air temperature or, in the case of closed circuit dry cooling towers, rely solely on air to cool the working fluid to near the dry-bulb air temperature.
Common applications include cooling the circulating water used in oil refineries, petrochemical and other chemical plants, thermal power stations and HVAC systems for cooling buildings. The main types of cooling towers are natural draft and induced draft cooling towers. The classification is based on the type of air induction into the tower.