Editing Cooling tower (section)

==Classification by use==
{{More citations needed section|date=May 2021}}
===Heating, ventilation and air conditioning (HVAC)===
[[File:Loop Shopping Centre Exterior I.jpg|thumb|Two HVAC cooling towers on the rooftop of a shopping center (Darmstadt, Hessen, Germany)]]
{{main|HVAC}}

[[File:Induced Draft Cooling Tower for HVAC.jpg|thumb|FRP cooling towers installed on roof top]]

[[File:Cooling Tower Fill Material.jpg|thumb|right|Cell of a cross-flow type cooling tower with fill material and circulating water visible]]

An [[HVAC]] (heating, ventilating, and air conditioning) cooling tower is used to dispose of ("reject") unwanted heat from a [[chiller]]. Liquid-cooled chillers are normally more energy efficient than air-cooled chillers due to [[heat rejection]] to tower water at or near [[wet-bulb temperature]]s.  Air-cooled chillers must reject heat at the higher [[dry-bulb temperature]], and thus have a lower average reverse–[[Carnot cycle|Carnot-cycle]] effectiveness. In hot climates, large office buildings, hospitals, and schools typically use cooling towers in their air conditioning systems.  Generally, industrial cooling towers are much larger than HVAC towers.
HVAC use of a cooling tower pairs the cooling tower with a liquid-cooled chiller or liquid-cooled condenser. A [[Refrigeration#Capacity ratings|''ton'' of air-conditioning]] is defined as the removal of {{convert|12,000|BTU/h|kW}}. The ''equivalent ton'' on the cooling tower side actually rejects about {{convert|15,000|BTU/h|kW}} due to the additional waste-heat–equivalent of the energy needed to drive the chiller's compressor. This ''equivalent ton'' is defined as the heat rejection in cooling {{convert|3|usgal/minute|L/minute|abbr=off}} or {{convert|1,500|lb/h|kg/h}} of water by {{convert|10|F-change|C-change}}, which amounts to {{convert|15,000|BTU/h|kW}}, assuming a chiller [[coefficient of performance]] (COP) of 4.0.<ref>{{cite book|last1=Cheremisinoff|first1=Nicholas|title=Handbook of Chemical Processing Equipment|date=2000|publisher=Butterworth-Heinemann|isbn=9780080523828|page=69}}</ref> This COP is equivalent to an energy efficiency ratio (EER) of 14.

Cooling towers are also used in HVAC systems that have multiple water source [[heat pumps]] that share a common piping ''water loop''. In this type of system, the water circulating inside the water loop removes heat from the condenser of the heat pumps whenever the heat pumps are working in the cooling mode, then the externally mounted cooling tower is used to remove heat from the water loop and reject it to the [[atmosphere]].  By contrast, when the heat pumps are working in heating mode, the condensers draw heat out of the loop water and reject it into the space to be heated.  When the water loop is being used primarily to supply heat to the building, the cooling tower is normally shut down (and may be drained or winterized to prevent freeze damage), and heat is supplied by other means, usually from separate [[boiler]]s.

===Industrial cooling towers===
[[File:Open loop Cooling Tower for DG Set.jpg|thumb|]]
[[File:Cenk Endustri Field Erected Industrial Cooling Tower.JPG|thumb|Industrial cooling towers for a power plant]]
[[File:Industrial Counterflow Cooling Towers.jpg|thumb|Industrial cooling towers for fruit processing]]
Industrial cooling towers can be used to remove heat from various sources such as machinery or heated process material.  The primary use of large, industrial cooling towers is to remove the heat absorbed in the circulating [[cooling water]] systems used in [[power plants]], [[oil refinery|petroleum refineries]], [[petrochemical]] plants, [[natural gas]] processing plants, food processing plants, semi-conductor plants, and for other industrial facilities such as in condensers of distillation columns, for cooling liquid in crystallization, etc.<ref>
{{Cite report |title=Profile of the Fossil Fuel Electric Power Generation Industry |url=http://www.epa.gov/compliance/resources/publications/assistance/sectors/notebooks/fossil.html |author=U.S. Environmental Protection Agency (EPA) |year= 1997 |publisher= United States }} Document No. EPA/310-R-97-007. p. 79.</ref> The circulation rate of cooling water in a typical 700 MW<sub>th</sub> [[coal-fired power plant]] with a cooling tower amounts to about 71,600 cubic metres an hour (315,000 US gallons per minute)<ref>[http://www.epa.gov/waterscience/presentations/maulbetsch.pdf Cooling System Retrofit Costs] EPA Workshop on Cooling Water Intake Technologies, John Maulbetsch, Maulbetsch Consulting, May 2003</ref> and the circulating water requires a supply water make-up rate of perhaps 5 percent (i.e., 3,600 cubic metres an hour, equivalent to one cubic metre every second).

If that same plant had no cooling tower and used '''once-through cooling'''<!--bad name; evaporative is also once-through--> water, it would require about 100,000 cubic metres an hour<ref>Thomas J. Feeley, III, Lindsay Green, James T. Murphy, Jeffrey Hoffmann, and Barbara A. Carney (2005). [http://204.154.137.14/technologies/coalpower/ewr/pubs/IEP_Power_Plant_Water_R&D_Final_1.pdf "Department of Energy/Office of Fossil Energy's Power Plant Water Management R&D Program."] {{webarchive|url=https://web.archive.org/web/20070927104349/http://204.154.137.14/technologies/coalpower/ewr/pubs/IEP_Power_Plant_Water_R%26D_Final_1.pdf |date=27 September 2007 }} U.S. Department of Energy, July 2005.</ref> A large cooling water intake typically kills millions of [[fish]] and [[larvae]] annually, as the organisms are impinged on the intake [[fish screen|screens]].<ref>The [[Indian Point Energy Center]] cooling system kills over a billion fish eggs and larvae annually. {{cite news |last=McGeehan |first=Patrick |date=2015-05-12 |title=Fire Prompts Renewed Calls to Close the Indian Point Nuclear Plant |url=https://www.nytimes.com/2015/05/13/nyregion/fire-prompts-renewed-calls-to-close-the-indian-point-nuclear-plant.html |newspaper=New York Times}}</ref> A large amount of water would have to be continuously returned to the ocean, lake or river from which it was obtained and continuously re-supplied to the plant. Furthermore, discharging large amounts of hot water may raise the temperature of the receiving river or lake to an unacceptable level for the local ecosystem. Elevated water temperatures can kill fish and other aquatic organisms (see ''[[thermal pollution]]''), or can also cause an increase in undesirable organisms such as invasive species of [[zebra mussel]]s or [[algae]]. 

A cooling tower serves to dissipate the heat into the atmosphere instead, so that wind and air diffusion spreads the heat over a much larger area than hot water can distribute heat in a body of water. Evaporative cooling water cannot be used for subsequent purposes (other than rain somewhere), whereas surface-only cooling water can be re-used.
Some coal-fired and [[nuclear power plant]]s located in [[coastal]] areas do make use of once-through ocean water. But even there, the offshore discharge water outlet requires very careful design to avoid environmental problems.

Petroleum refineries may also have very large cooling tower systems. A typical large refinery processing 40,000 metric tonnes of crude oil per day ({{convert|300000|oilbbl}} per day) circulates about 80,000 cubic metres of water per hour through its cooling tower system.

The world's tallest cooling tower is the {{convert|210|m|ft}} tall cooling tower of the [[Pingshan Power Station|Pingshan II Power Station]] in [[Huaibei]], Anhui Province, China.<ref>{{cite web|url=https://www.hamon.com/cases-studies/largest-cooling-tower-in-the-world/#:~:text=Pingshan%20II%20is%20the%20largest,coal%20fired%20unit%20ever%20built |title=Pingshan II: the largest Cooling Tower in the world designed by Hamon |publisher=Hamon.com |date= |accessdate=2023-01-14}}</ref>
[[File:Field erected cooling tower.JPG|thumb|Field-erected cooling tower]]