TOWER is a special type of heat exchanger in which the warm water and the air are brought in direct contact for ‘evaporative cooling’. It provides a very good contact of air and water in terms of the contact area and mass TRANSFER coefficient of water vapour while keeping air pressure drop low.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.