- Key People:
- H.L. Callendar
- Related Topics:
- water
- superheated steam
- water vapor
steam
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What is steam?
Steam is an invisible gas formed when water is heated to its boiling point. It becomes visible when mixed with water droplets, appearing as a white, cloudy vapor.
Steam is produced naturally by geothermal activity, such as in hot springs and volcanoes, and artificially in technological systems like power plants. In power plants, steam drives turbines to produce electricity, and it's also used in various industrial processes, like refining petroleum, and in homes for heating and cooking.
Superheated steam is steam heated above its condensation temperature; at normal atmospheric pressure, its temperature exceeds 100 °C (212 °F). Because of water's high boiling point and high latent heat of vaporization, steam is an efficient energy source.
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How is steam formed?
Steam, an odorless, invisible gas, is vaporized water that is usually mixed with small water droplets, giving it a cloudy appearance. Steam forms when water reaches its boiling point and gains enough heat to turn into a gas.
The transformation from liquid water to steam occurs in stages. Initially, heat raises the water's temperature to its boiling point, creating a saturated liquid. Further heating causes the liquid to vaporize into steam. During this two-phase region, the temperature remains constant as more liquid turns to vapor. Once all liquid is vaporized, the steam becomes a saturated vapor. Additional heat then increases both the temperature and volume, resulting in superheated steam.
Steam is produced naturally through geothermal activity, such as in hot springs, geysers, and volcanoes. It is also generated on a large scale in technological systems like fossil-fuel-burning boilers and nuclear reactors.
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What is the difference between steam and water vapor?
Steam is an invisible gas consisting of vaporized water, often mixed with minute water droplets, giving it a cloudy appearance. It forms naturally when underground water is heated by volcanic activity, emerging from hot springs and volcanoes. Steam can also be produced by technological systems like fossil-fuel-burning boilers and nuclear reactors.
Water vapor is simply the gaseous state of water. It is an invisible conductor that carries water from sea to land, making terrestrial life possible. The amount of water vapor in the atmosphere is influenced by air temperature, with warmer temperatures leading to greater evaporation rates and higher concentrations of water vapor.
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How is steam used to produce electricity in power plants?
In power plants, steam is used to spin turbines connected to electrical generators. The steam exerts force against the blades, turning the rotor and converting thermal energy into mechanical energy, which in turn is converted into electricity.
There are multiple methods to generate electricity using steam:
* Dry steam plants directly funnel steam from the ground to a turbine that drives a generator.
* Flash steam plants extract high-temperature water from the ground, which then vaporizes into steam via a sudden pressure decrease. The steam is then used to power the turbine-generator set.
* Binary cycle plants use heat from geothermal water to vaporize a secondary working fluid, which then drives the turbine. After the vapor passes through the turbine, it is recondensed and piped back to the heat exchanger.5 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
Why does steam cause burns?
Steam causes burns because of its high heat-carrying capacity. When steam comes into contact with skin, it releases a large amount of energy as it condenses back into water. This energy transfer occurs rapidly, leading to a quick increase in the skin's temperature, which can damage skin cells and result in burns.
The severity of a burn depends on the extent of tissue destruction and the amount of body surface affected. Burns are categorized as first-, second-, or third-degree injuries, depending on the depth of skin damage.
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What are some other common uses of steam in daily life and industry?
Steam has diverse applications in daily life and industry. In homes, it has been used for cooking and heating. Industries use steam for various processes, including the manufacture of steel, aluminum, copper, and nickel, chemical production, and petroleum refining. Moreover, steam systems in buildings use steam generated in a boiler that is then piped to radiators, with the condensed steam being returned to the boiler for recirculation. Steam is also used to sterilize liquid foods and food packaging. Another use is in cogeneration systems, where steam is used for both power generation and heating.
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steam, odourless, invisible gas consisting of vaporized water. It is usually interspersed with minute droplets of water, which gives it a white, cloudy appearance. In nature, steam is produced by the heating of underground water by volcanic processes and is emitted from hot springs, geysers, fumaroles, and certain types of volcanoes. Steam also can be generated on a large scale by technological systems, as, for example, those employing fossil-fuel-burning boilers and nuclear reactors.
Steam power constitutes an important power source for industrial society. Water is heated to steam in power plants, and the pressurized steam drives turbines that produce electrical current. The thermal energy of steam is thus converted to mechanical energy, which in turn is converted into electricity. The steam used to drive turbogenerators furnishes most of the world’s electric power. Steam is also widely employed in such industrial processes as the manufacture of steel, aluminum, copper, and nickel; the production of chemicals; and the refining of petroleum. In the home, steam has long been used for cooking and heating.
The stages that occur during the transformation of liquid water to its vapour (steam) are shown in the , in which A–E depict a cylindrical vessel containing a fixed quantity of water subject to the constant pressure exerted by a weighted (W) movable piston. A′–E′ are corresponding points on a graph showing, for a range of pressures and volumes, whether a specific mass of water is entirely liquid, entirely vapour, or a mixture of the two phases. A and A′ represent this system under conditions of pressure, volume, and temperature such that the water is entirely in the subcooled liquid state; that is, the temperature is below the boiling point of water at the prevailing pressure. The addition of heat causes the water to expand slightly and the temperature to rise until the water reaches its boiling point; at this stage, represented by B and B′, the water is said to be in the saturated liquid state. If more heat is added, boiling begins: the liquid starts to vaporize (turn into steam), forcing the piston upward more rapidly than before, as illustrated in C.
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Steam is useful in power generation because of the unusual properties of water. The manifold hydrogen bonds among water molecules mean that water has a high boiling point and a high latent heat of vaporization compared with other liquids; that is, it takes considerable heat to turn liquid water into steam, which is available when the steam is condensed. The boiling point and the heat of vaporization both depend on ambient pressure. At standard atmospheric pressure of 101 kilopascals (14.7 pounds per square inch), water boils at 100 °C (212 °F). At higher or lower pressures, more or less molecular energy, respectively, is required to allow water molecules to escape from the liquid to the gaseous state. Correspondingly, the boiling point becomes lower or higher. The heat of vaporization, defined as the amount of energy needed to evaporate a unit mass of liquid (in engineering practice, a unit weight), also varies with pressure. At standard atmospheric pressure it is 2,260 kilojoules per kg (972 BTU [British thermal units] per pound).