physical chemistry, and in engineering, steam refers to vaporized water. It is a pure, completely invisible gas (for mistsee below). At standard temperature and pressure, pure steam (unmixed with air, but in equilibrium with liquid water) occupies about 1,600 times the volume of an equal mass of liquid water. In the atmosphere, the partial pressureof water is much lower than 1 atm, therefore gaseous water can exist at temperatures much lower than 100 C (see water vaporand humidity).
"In common speech," steam most often refers to the white
mistthat condenses above boiling water as the hot vapor ("steam" in the first sense) mixes with the cooler air. This mist is made of tiny droplets of liquid water, not gaseous water, so it is no longer technically steam. In the spout of a steaming kettle, the spot where there is no condensed water vapor, where there appears to be nothing there, is steam.
steam engineuses the expansion of steam in order to drive a pistonor turbineto perform mechanical work. 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 energy because of water's high heat of vaporization. The ability to return condensed steam as water-liquid to the boiler at high pressure with relatively little expenditure of pumping power is also important. Engineers use an idealised thermodynamic cycle, the Rankine cycle, to model the behaviour of steam engines.
In the U.S., more than 86% of electric power is produced using steam as the
working fluid, nearly all by steam turbines. Condensation of steam to water often occurs at the low-pressure end of a steam turbine, since this maximises the energy efficiency, but such wet-steam conditions have to be limited to avoid excessive turbine blade erosion.
When liquid water comes in contact with a very hot substance (such as
lava, or molten metal) it can flash into steam very quickly; this is called a steam explosion. Such an explosion was probably responsible for much of the damage in the Chernobyl accidentand for many so-called 'foundry accidents'.
Steam's capacity to transfer heat is also used in the home: for cooking vegetables, steam cleaning of fabric and carpets, and heating buildings. In each case, water is heated in a boiler, and the steam carries the energy to a target object. "
Steam showers" are actually low-temperature mist-generators, and do not actually use steam.
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, steam is piped into buildings to provide heat energy after its use in the electric generation cycle. The world's biggest steam generation system is Con Edisonin New York Citywhich pumps steam into 100,000 buildings in Manhattanfrom seven cogeneration plants. [Carl Bevelhymer, [http://www.gothamgazette.com/article/issueoftheweek/20031110/200/674 "Steam"] , " Gotham Gazette", November 10, 2003]
Food steameror steam cooker
IAPWS—"an association that maintains international-standard correlations for the thermodynamicproperties of steam, including IAPWS-IF97 (for use in industrial simulation and modelling) and IAPWS-95 (a general purpose and scientific correlation)."
Nuclear power—and power plants "use steam to generate electricity"
Psychrometrics—"moist air/vapour mixtures, humidity and air conditioning"
* [http://webbook.nist.gov/chemistry/fluid/ Steam Tables & Charts by National Institute of Standards and Technology, NIST]
* [http://www.spiraxsarco.com/resources/steam-engineering-tutorials/steam-engineering-principles-and-heat-transfer/what-is-steam.asp What Is Steam?] "(general article about the properties of water/steam)"
* [http://www.cheresources.com/steam_tracing.shtml Steam Tracing]
* [http://www.spiraxsarco.com/resources/steam-tables.asp Online steam properties] calculator (Spirax Sarco)
* [http://twt.mpei.ac.ru/ochkov/WSPHB/Engindex.html] Steam Tables & Charts with Mathcad Calculation server
* [http://www.steamtablesonline.com Free Steam Tables Online] calculator based on IAPWS-IF97 (MegaWatSoft)
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Look at other dictionaries:
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Steam — (st[=e]m), n. [OE. stem, steem, vapor, flame, AS. ste[ a]m vapor, smoke, odor; akin to D. stoom steam, perhaps originally, a pillar, or something rising like a pillar; cf. Gr. sty ein to erect, sty^los a pillar, and E. stand.] 1. The elastic, a[… … The Collaborative International Dictionary of English
STEAM — Développeurs Valve Corporation Première version 12 … Wikipédia en Français
Steam — Desarrollador Valve Corporation store.steampowered.com … Wikipedia Español
steam — [stēm] n. [ME steme < OE steam, akin to Du stoom, WFris steam] 1. Obs. a vapor, fume, or exhalation 2. a) water as converted into an invisible vapor or gas by being heated to the boiling point; vaporized water: it is used for heating, cooking … English World dictionary
steam — ► NOUN 1) the hot vapour into which water is converted when heated, which condenses in the air into a mist of minute water droplets. 2) the expansive force of this vapour used as a source of power for machines. 3) momentum; impetus: the dispute… … English terms dictionary
steam´i|ly — steam|y «STEE mee», adjective, steam|i|er, steam|i|est. 1. of steam; like steam: »a steamy vapor. 2. full of steam; giving off steam; rising in steam: »a steamy room … Useful english dictionary
steam|y — «STEE mee», adjective, steam|i|er, steam|i|est. 1. of steam; like steam: »a steamy vapor. 2. full of steam; giving off steam; rising in steam: »a steamy room … Useful english dictionary
Steam — (st[=e]m), v. t. 1. To exhale. [Obs.] Spenser. [1913 Webster] 2. To expose to the action of steam; to apply steam to for softening, dressing, or preparing; as, to steam wood; to steamcloth; to steam food, etc. [1913 Webster] … The Collaborative International Dictionary of English