Editing Cooling tower (section)

==Heat transfer methods==
{{Unreferenced section|date=April 2021}}
With respect to the [[heat transfer]] mechanism employed, the main types are:
* '''Wet cooling towers''' or '''open-circuit Cooling Tower''' or '''evaporative cooling towers''' operate on the principle of [[evaporative cooling]].  The working [[coolant]] (usually water) is the evaporated fluid, and is exposed to the elements.
* '''Closed circuit cooling towers''' (also called '''fluid coolers''') pass the working coolant through a large [[heat exchanger]], usually a [[radiator]], upon which clean water is sprayed and a fan-induced draft applied.  The resulting heat transfer performance is close to that of a wet cooling tower, with the advantage of protecting the working fluid from environmental exposure and contamination. 
* '''[[Adiabatic]] cooling towers''' spray water into the incoming air or onto a cardboard pad to cool the air before it passes over an air-cooled heat exchanger. Adiabatic cooling towers use less water than other cooling towers but do not cool the fluid as close to the wet bulb temperature. Most adiabatic cooling towers are also hybrid cooling towers.
* '''Dry cooling towers''' (or '''dry coolers''') are closed circuit cooling towers which operate by [[heat transfer]] through a heat exchanger that separates the working coolant from ambient air, such as in a radiator, utilizing convective heat transfer. They do not use evaporation and are air-cooled heat exchangers.
*'''Hybrid cooling towers''' or '''wet-dry cooling towers''' are closed circuit cooling towers that can switch between wet or adiabatic and dry operation. This helps balance water and energy savings across a variety of weather conditions. Some hybrid cooling towers can switch between dry, wet, and adiabatic modes. Thermal efficiencies up to 92% have been observed in hybrid cooling towers.<ref>{{Cite journal|last=Gul|first=S.|date=2015-06-18|title=Optimizing the performance of Hybrid: Induced-Forced Draft Cooling Tower|url=http://www.piche.org.pk/journal/index.php?journal=jpiche&page=article&op=view&path%5B%5D=192|journal=Journal of the Pakistan Institute of Chemical Engineers|language=en|volume=43|issue=2|issn=1813-4092}}</ref>

In a wet cooling tower (or open circuit cooling tower), the warm water can be cooled to a temperature ''lower'' than the ambient air dry-bulb temperature, if the air is relatively dry (see [[dew point]] and [[psychrometrics]]). As ambient air is drawn past a flow of water, a small portion of the water evaporates, and the energy required to evaporate that portion of the water is taken from the remaining mass of water, thus reducing its temperature. Approximately {{convert|970|BTU/lb|kJ/kg|order=flip}} of heat energy is absorbed for the evaporated water. Evaporation results in saturated air conditions, lowering the temperature of the water processed by the tower to a value close to [[wet-bulb temperature]], which is lower than the ambient [[dry-bulb temperature]], the difference determined by the initial humidity of the ambient air.

To achieve better performance (more cooling), a medium called ''fill'' is used to increase the surface area and the time of contact between the air and water flows. ''Splash fill'' consists of material placed to interrupt the water flow causing splashing. ''Film fill'' is composed of thin sheets of material (usually [[polyvinyl chloride|PVC]]) upon which the water flows.  Both methods create increased surface area and time of contact between the fluid (water) and the gas (air), to improve heat transfer.