View source for Steam

{{Short description|Water in the gas phase}}
{{About|water as a gas|the video game distribution platform|Steam (service)|other uses}}
[[File:Steam phase eruption of Castle Geyser.jpg|thumb|300px|Liquid phase eruption of [[Castle Geyser]] in [[Yellowstone Park]]]]

'''Steam''' is [[water vapor]], often mixed with [[air]] or an [[aerosol]] of liquid [[water]] droplets. This may occur due to [[evaporation]] or due to [[boiling]], where heat is applied until water reaches the [[enthalpy of vaporization]]. Saturated or [[superheated steam]] is invisible; however, wet steam, a visible [[mist]] or aerosol of water droplets, is often referred to as  "steam".<ref name=oed>{{Cite OED|steam|id=189475}}</ref>{{rp|6}}

When liquid water becomes steam, it increases in [[volume]] by 1,700 times at [[standard temperature and pressure]]; this change in volume can be converted into [[work (physics)|mechanical work]] by [[steam engine]]s such as [[reciprocating engine|reciprocating piston type engines]] and [[steam turbine]]s, which are a sub-group of steam engines. Piston type steam engines played a central role in the [[Industrial Revolution]] and modern steam turbines are used to generate more than 80% of the world's electricity. If liquid water comes in contact with a very hot surface or depressurizes quickly below its [[vapor pressure|vapour pressure]], it can create a [[steam explosion]].

==Types of steam and conversions==
Steam is traditionally created by heating a boiler via burning coal and other fuels, but it is also possible to create steam with solar energy.<ref>{{cite journal |doi=10.1016/j.ijthermalsci.2012.01.012 |title=Characterization of light-induced, volumetric steam generation in nanofluids |year=2012 |last1=Taylor |first1=Robert A. |last2=Phelan |first2=Patrick E. |last3=Adrian |first3=Ronald J. |last4=Gunawan |first4=Andrey |last5=Otanicar |first5=Todd P. |journal=International Journal of Thermal Sciences |volume=56 |pages=1–11|bibcode=2012IJTS...56....1T }}</ref><ref>{{cite journal |doi=10.1063/1.3571565 |title=Applicability of nanofluids in high flux solar collectors |year=2011 |last1=Taylor |first1=Robert A. |last2=Phelan |first2=Patrick E. |last3=Otanicar |first3=Todd P. |last4=Walker |first4=Chad A. |last5=Nguyen |first5=Monica |last6=Trimble |first6=Steven |last7=Prasher |first7=Ravi |journal=Journal of Renewable and Sustainable Energy |volume=3 |issue=2 |pages=023104 |url=https://digitalcommons.lmu.edu/cgi/viewcontent.cgi?article=1019&context=mech_fac |access-date=2022-06-14 |archive-date=2022-12-02 |archive-url=https://web.archive.org/web/20221202161644/https://digitalcommons.lmu.edu/cgi/viewcontent.cgi?article=1019&context=mech_fac |url-status=live |url-access=subscription }}</ref><ref>{{cite journal |doi=10.1063/1.3250174 |title=Vapor generation in a nanoparticle liquid suspension using a focused, continuous laser |year=2009 |last1=Taylor |first1=Robert A. |last2=Phelan |first2=Patrick E. |last3=Otanicar |first3=Todd |last4=Adrian |first4=Ronald J. |last5=Prasher |first5=Ravi S. |journal=Applied Physics Letters |volume=95 |issue=16 |pages=161907 |bibcode=2009ApPhL..95p1907T |url=https://works.bepress.com/todd_otanicar/1/download/ |url-access=subscription }}{{Dead link|date=January 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> Water vapour that includes water droplets is described as '''wet steam'''. As wet steam is heated further, the droplets evaporate, and at a high enough temperature (which depends on the pressure) all of the water evaporates and the system is in [[vapor–liquid equilibrium|vapour–liquid equilibrium]].<ref>{{cite book |last=Singh |first=R Paul |year=2001 |title=Introduction to Food Engineering |publisher=Academic Press |isbn=978-0-12-646384-2}}{{page needed|date=September 2013}}</ref> When steam has reached this equilibrium point, it is referred to as '''saturated steam'''.

[[Superheated steam]] or [[live steam]] is steam at a temperature higher than its [[boiling point]] for the pressure, which only occurs when all liquid water has evaporated or has been removed from the system.<ref>{{cite web |url=http://www.spiraxsarco.com/resources/steam-engineering-tutorials/steam-engineering-principles-and-heat-transfer/superheated-steam.asp |title=Superheated Steam |publisher=[[Spirax-Sarco Engineering]] |access-date=2009-03-23 |archive-date=2007-03-04 |archive-url=https://web.archive.org/web/20070304022436/http://www.spiraxsarco.com/resources/steam-engineering-tutorials/steam-engineering-principles-and-heat-transfer/superheated-steam.asp |url-status=live }}</ref>

[[Steam table]]s <ref>{{cite book |last=Malhotra |first=Ashok |author-link=Ashok Malhotra (professor) |year=2012 |title=Steam Property Tables: Thermodynamic and Transport Properties |publisher=CreateSpace Independent Publishing Platform |isbn=978-1-479-23026-6}}{{page needed|date=September 2013}}</ref> contain thermodynamic data for water/saturated steam and are often used by engineers and scientists in design and operation of equipment where thermodynamic cycles involving steam are used.  Additionally, thermodynamic [[phase diagram]]s for water/steam, such as a temperature-entropy diagram or a [[Enthalpy–entropy_chart|Mollier diagram]] shown in this article, may be useful. Steam charts are also used for analysing thermodynamic cycles.

{| class="wikitable"
|  [[File:Mollier enthalpy entropy chart for steam - US units.svg|thumb|300px]] || [[File:Pressure-enthalpy chart for steam, in US units.svg|thumb|300px]] || [[File:Temperature-entropy chart for steam, imperial units.svg|thumb|300px]]
|-
| [[Enthalpy–entropy_chart|Enthalpy-entropy (h-s) diagram]] for steam || Pressure-enthalpy (p-h) diagram for steam || Temperature-entropy (T-s) diagram for steam
|}

==Uses==

===Agricultural===
In [[agriculture]], steam is used for [[soil steam sterilization|soil sterilization]] to avoid the use of harmful chemical agents and increase [[soil health]].<ref>{{cite journal |last1=van Loenen |first1=Mariska C.A. |last2=Turbett |first2=Yzanne |last3=Mullins |first3=Chris E. |last4=Feilden |first4=Nigel E.H. |last5=Wilson |first5=Michael J. |last6=Leifert |first6=Carlo |last7=Seel |first7=Wendy E. |date=2003-11-01 |title=Low Temperature–Short Duration Steaming of Soil Kills Soil-Borne Pathogens, Nematode Pests and Weeds |url=https://link.springer.com/article/10.1023/B:EJPP.0000003830.49949.34 |journal=European Journal of Plant Pathology |language=en |volume=109 |issue=9 |pages=993–1002 |doi=10.1023/B:EJPP.0000003830.49949.34 |bibcode=2003EJPP..109..993V |s2cid=34897804 |issn=1573-8469 |access-date=2022-06-14 |archive-date=2022-04-12 |archive-url=https://web.archive.org/web/20220412070736/https://link.springer.com/article/10.1023/B:EJPP.0000003830.49949.34 |url-status=live |url-access=subscription }}</ref>

===Domestic===
[[Image:Boilingkettle.jpg|thumb|300px|Boiling water creating steam in an electric kettle]]
Steam's capacity to transfer heat is also used in the home: for cooking vegetables, steam cleaning of fabric, carpets and flooring, and for heating buildings.  In each case, water is heated in a boiler, and the steam carries the energy to a target object. Steam is also used in ironing clothes to add enough humidity with the heat to take wrinkles out and put intentional creases into the clothing.

===Electricity generation (and co-generation)===
As of 2000 around 90% of all electricity was generated using steam as the [[working fluid]], nearly all by steam turbines.<ref Name="Wiser">{{cite book |title=Energy resources: occurrence, production, conversion, use |last=Wiser |first=Wendell H. |year=2000 |publisher=Birkhäuser |isbn=978-0-387-98744-6 |chapter=Energy Source Contributions to Electric Power Generation |page=190 |chapter-url=https://books.google.com/books?id=UmMx9ixu90kC&pg=PA190 |access-date=2016-02-22 |archive-date=2023-01-23 |archive-url=https://web.archive.org/web/20230123202054/https://books.google.com/books?id=UmMx9ixu90kC&pg=PA190 |url-status=live }}</ref>

In electric generation, steam is typically condensed at the end of its expansion cycle, and returned to the boiler for re-use.  However, in [[cogeneration|co-generation]], steam is piped into buildings through a [[district heating]] system to provide heat energy after its use in the electric generation cycle.  The world's biggest steam generation system is the [[New York City steam system]], which pumps steam into 100,000 buildings in [[Manhattan]] from seven co-generation plants.<ref>{{cite web |first=Carl |last=Bevelhymer |url=https://www.gothamgazette.com/index.php/government/2104-steam |title=Steam |website=[[Gotham Gazette]] |date=November 10, 2003 |access-date=June 14, 2022 |archive-date=January 23, 2023 |archive-url=https://web.archive.org/web/20230123202058/https://www.gothamgazette.com/index.php/government/2104-steam |url-status=live }}</ref>

===Energy storage===
[[File:Dampfspeicherlok Genthin Henkel Werk.jpg|thumb|[[Fireless locomotive#Steam|Fireless steam locomotive]]<br>Despite the resemblance to a boiler, note the lack of a chimney and also how the cylinders are at the cab end, not the chimney end.]]
In other industrial applications steam is used for [[energy storage]], which is introduced and extracted by heat transfer, usually through pipes. Steam is a capacious reservoir for thermal energy because of water's high [[heat of vaporization]].

[[Fireless locomotive#Steam|Fireless steam locomotive]]s were [[steam locomotive]]s that operated from a supply of steam stored on board in a large tank resembling a conventional locomotive's boiler. This tank was filled by [[process steam]], as is available in many sorts of large factory, such as [[paper mill]]s. The locomotive's propulsion used pistons and connecting rods, as for a typical steam locomotive. These locomotives were mostly used in places where there was a risk of fire from a boiler's firebox, but were also used in factories that simply had a plentiful supply of steam to spare.

===Mechanical effort===
Steam engines and steam turbines use the expansion of steam to drive a [[piston]] or turbine to perform [[mechanical work]]. The ability to return condensed steam as water-liquid to the boiler at high pressure with relatively little expenditure of pumping power is  important. [[Condensation]] of steam to water often occurs at the low-pressure end of a steam turbine, since this maximizes the [[Energy conversion efficiency|energy efficiency]], but such wet-steam conditions must be limited to avoid excessive turbine blade erosion. Engineers use an idealised [[thermodynamic cycle]], the [[Rankine cycle]], to model the behaviour of steam engines. Steam turbines are often used in the production of electricity.

===Sterilization===
An [[autoclave]], which uses steam under pressure, is used in microbiology laboratories and similar environments for [[sterilization (microbiology)|sterilization]].

Steam, especially dry (highly superheated) steam, may be used for antimicrobial cleaning even to the levels of sterilization.  Steam is a non-toxic antimicrobial agent.<ref>EP Patent Publication 2,091,572</ref>
<ref>{{cite journal |doi=10.1016/j.ajic.2011.11.013 |title=Biofilms on environmental surfaces: Evaluation of the disinfection efficacy of a novel steam vapor system |year=2012 |last1=Song |first1=Liyan |last2=Wu |first2=Jianfeng |last3=Xi |first3=Chuanwu |journal=American Journal of Infection Control |volume=40 |issue=10 |pages=926–30 |pmid=22418602}}</ref>

===Steam in piping===
Steam is used in piping for utility lines. It is also used in jacketing and tracing of piping to maintain the uniform temperature in pipelines and vessels.

=== Industrial Processes ===
Steam is used across multiple industries for its ability to transfer heat to drive chemical reactions, sterilize or disinfect objects and to maintain constant temperatures. In the lumber industry, steam is used in the process of [[steam bending|wood bending]], killing insects, and increasing plasticity. Steam is used to accentuate drying of concrete especially in prefabricates.
Care should be taken since concrete produces heat during hydration and additional heat from the steam could be detrimental to hardening reaction processes of the concrete. In chemical and [[petrochemical industry|petrochemical industries]], steam is used in various chemical processes as a reactant. [[Steam cracking]] of long chain hydrocarbons produces lower molecular weight hydrocarbons for fuel or other chemical applications. [[Steam reforming]] produces [[syngas]] or [[hydrogen]].

===Cleaning===
Used in cleaning of fibers and other materials, sometimes in preparation for painting. Steam is also useful in melting hardened grease and oil residues, so it is useful in cleaning kitchen floors and equipment and internal combustion engines and parts. Among the advantages of using steam versus a hot water spray are the facts that steam can operate at higher temperatures and it uses substantially less water per minute.<ref>{{cite web |title=Why Steam? |url=http://www.sioux.com/why-steam.html |website=Sioux Corporation Website |publisher=Sioux Corporation |access-date=24 September 2015 |archive-date=31 December 2017 |archive-url=https://web.archive.org/web/20171231054821/http://www.sioux.com/why-steam.html |url-status=live }}</ref>

==See also==
*[[Electrification]]
*[[Food steamer]] or steam cooker
*[[Geyser]]—''geothermally-generated steam''
*[[IAPWS]]—''an association that maintains international-standard correlations for the [[thermodynamic]] properties of steam, including IAPWS-IF97 (for use in industrial simulation and modelling) and IAPWS-95 (a general purpose and scientific correlation).''
*[[Industrial Revolution]]
*[[Live steam]]
*[[Mass production]]
*[[Nuclear power]]—and [[power plant]]s ''use steam to generate electricity''
*[[Oxyhydrogen]]
*[[Psychrometrics]]—''moist air–vapor mixtures, humidity, and air conditioning''
*[[Steam–electric power station]]
*[[Steam locomotive]]
*[[Sterilization (microbiology)]]

==References==
{{Reflist}}

==External links==
{{Commons category multi|Steam|Water vapor}}
{{Wiktionary|steam|steamed}}
{{Wikivoyage|Steam power}}
*[https://webbook.nist.gov/chemistry/fluid/ Thermophysical Properties of Fluid Systems], Steam Tables & Charts by National Institute of Standards and Technology, NIST
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|links=[[v:Engineering thermodynamics/Steam tables|Wikiversity has steam tables with figures and Matlab code]]
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{{Water}}

[[Category:Steam power|*]]
[[Category:Forms of water]]
[[Category:Gases]]
[[Category:Water in gas]]