Basic work principle of Natural Draught cooling tower (NDCT)

 

The main principle of Cooling tower based on evaporation. A cooling tower’s function is to remove heat from a building or process application that generates heat and must be dissipated. Cooling towers uses the heat transfer method of convection and surface area contact between fluids to help cool water cycling back from the source that is to be cooled to a suitable temperature to re-carry heat. In this process the sensible heat of hot water is converted to latent heat of vaporisation. The fundamental principal employed in accomplishing this removal of heat is the evaporation of water. How this evaporation is accomplished varies among differing types of cooling towers but nearly all towers rely upon the atomization of the water over sprinkler heads, allowing the water to “rain” over fills which are a honeycomb-like structure that increases the surface area of the water , and then pulling air across the surface of the water through the use of fans.

 Cooling towers are used mainly when there is no water source available for cooling. This could be due to lack of water resources in the country itself. In this cooling process there is loss of water both due to evaporation and entrainment. To minimize the entrainment losses drift eliminators is fitted into the tower.