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Topic: Convection


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  Educator's Guide to Convection
The convection that students are most likely to have observed is in cumulonimbus clouds or "thunderheads." These towering vertical clouds can be seen to evolve over a few minutes.
Thunderheads and granulation are large-scale examples of convection.
Convection acts as described in the examples above where gravity's effects are present (so that warm, low density fluids can rise and cool, high density fluids can fall).
www.solarviews.com /eng/edu/convect.htm   (567 words)

  
  Convection - Wikipedia, the free encyclopedia
Convection is one of the three mechanisms of heat transfer, the others being conduction and radiation.
Convection occurs in atmospheres, oceans, and planetary mantles.
Convection, especially Rayleigh-Bénard convection, where the convecting fluid is contained by two rigid horizontal plates, is a convenient example of a pattern forming system.
en.wikipedia.org /wiki/Convection   (1097 words)

  
 Your single source for convection ovens.
Convection ovens use convective heat transfer, whether the energy source is gas, electric, or steam.
Convection is the indirect transfer of thermal energy by the circulation of a heated carrier, such as air.
In contrast to natural convection ovens, where air flows incidentally as the result of the heat, forced convection is the intentional flow of air provided by fans and blowers.
www.thermovation.com /pages/convectionovens.html   (414 words)

  
 AMS Glossary
Distinction is made between free convection (gravitational or buoyant convection), motion caused only by density differences within the fluid; and forced convection, motion induced by mechanical forces such as deflection by a large-scale surface irregularity, turbulent flow caused by friction at the boundary of a fluid, or motion caused by any applied pressure gradient.
Moist convection in the atmosphere is characterized by deep, saturated updrafts and downdrafts, and unsaturated downdrafts driven largely by the evaporation and melting of precipitation.
Moist convection and radiation are the dominant modes of vertical heat transport in the Tropics.
amsglossary.allenpress.com /glossary/search?p=1&query=convection   (489 words)

  
 Convection oven - Wikipedia, the free encyclopedia
Convection ovens/fan ovens heat air that is then circulated in the oven by an embedded high temperature fan.
By moving heated air past the food, convection ovens can operate at a lower temperature than a standard conventional oven and they can cook food more quickly.
Convection ovens demand a premium with basic home models costing approximately 40% more than a functionally equivalent conventional oven.
en.wikipedia.org /wiki/Convection_oven   (218 words)

  
 All about Convection Ovens - Keidel Bath, Plumbing, Kitchen - Cincinnati, OH
Convection ovens have been popular in Europe and in restaurants for years, but were introduced to the US residential market in 1978 by the Jenn-Air Corporation.
Convection occurs when another medium or fluid is used to convey the heat from the source to the food, as in water boiling in a pot, or hot air moving in an oven, which in turn heats the food.
As food is heated in an oven, an insulation barrier forms on the surface of the food, caused by the heat exchange between the hot air and the cold food and by the evaporation of moisture in the food.
www.keidel.com /design/select/ovens-convection.htm   (2323 words)

  
 Convection
Convection is the flow of heat through a bulk, macroscopic movement of matter from a hot region to a cool region, as opposed to the microscopic transfer of heat between atoms involved with conduction.
When the stove is first turned on heat is transferred first by conduction between the element through the bottom of the pot to the water.
An important example of convection currents that can be interpreted in this manner is the creation of breezes over land masses next to large bodies of water.
theory.uwinnipeg.ca /mod_tech/node76.html   (483 words)

  
 National Weather Service Fort Worth Glossary
In meteorology, the term is used specifically to describe vertical transport of heat and moisture, especially by updrafts and downdrafts in an unstable atmosphere.
The terms "convection" and "thunderstorms" often are used interchangeably, although thunderstorms are only one form of convection.
Convection which occurs without cloud formation is called dry convection, while the visible convection processes referred to above are forms of moist convection.
www.srh.noaa.gov /fwd/glossary/def/convection.htm   (98 words)

  
 convection. The Columbia Encyclopedia, Sixth Edition. 2001-05
Convection depends on the fact that, in general, fluids expand when heated and thus undergo a decrease in density (since a given volume of the fluid contains less matter at a higher temperature than at the original, lower temperature).
Thus, a current, called a convection current, becomes established in the fluid, with warmer, less dense fluid continually rising from the point of application of heat and cooler, denser portions of the fluid flowing outward and downward to replace the warmer fluid.
For example, when a portion of the atmosphere becomes heated by contact with a warm area of land, it rises into the cooler, higher altitudes, with the result that some of the moisture carried with it may be condensed to form clouds and precipitation.
www.bartleby.com /65/co/convecti.html   (307 words)

  
 Convection Ovens at BigTray
Convection ovens are available in gas or electric and in various configurations, including full-size, half-size, stackable, and as part of a traditional bake oven.
Convection ovens are highly versatile and ideal for cooking, warming, roasting, re-thermalizing and baking.
With a convection oven, you'll generally see about a 25 to 30% decrease in cooking temperature and a 20% decrease in cooking time when compared to a conventional oven.
www.bigtray.com /buyers_guide.asp?catid=110140&descatid=10850   (430 words)

  
 Convection Summary
The basic premise behind free convection is that heated fluid becomes more buoyant and "rises," while cooler fluid "sinks." Free convection occurs in any liquid or gas which expands or contracts in response to changing temperatures when it is exposed to multiple temperatures in an acceleration field such as gravity or a centrifuge.
Oceanic convection is also frequently driven by density differences due to varying salinity, known as thermohaline convection, and is of crucial importance in the global thermohaline circulation.
Convection, especially Rayleigh-Bénard convection, where the convecting fluid is contained by two rigid horizontal plates, is a convenient example of a pattern forming system.
www.bookrags.com /Convection   (1348 words)

  
 Heat Transfer
Convection is heat transfer by mass motion of a fluid such as air or water when the heated fluid is caused to move away from the source of heat, carrying energy with it.
Convection is thought to play a major role in transporting energy from the center of the Sun to the surface, and in movements of the hot magma beneath the surface of the earth.
The granules are described as convection cells which transport heat from the interior of the Sun to the surface.
hyperphysics.phy-astr.gsu.edu /hbase/thermo/heatra.html   (441 words)

  
 Convection in the Earth
Numerical experiments show that mantle convection is controlled from the top by continents, cooling lithosphere, slabs and plate motions and that plates not only drive and break themselves but can control and reverse convection in the mantle (1-6).
The mantle is generally considered to convect as a single layer (whole mantle convection) or, at most two (the standard geochemical model).
Convective flows driven by this mechanism can reach speeds of 15 cm/yr and may explain volcanism at the margins of continents and cratons, and at oceanic and continental rifts.
www.mantleplumes.org /Convection.html   (3674 words)

  
 Convection
Convection of heat energy in the atmosphere involves the movement of air.
Air is a poor conductor of energy, so convection is a major process of energy movement in the Earth’s atmosphere.
In the atmosphere, convection occurs when a shallow layer of air in contact with a hot surface warms by conduction, acquires buoyancy (warmer air is less dense than colder air), and rises, taking with it the energy that it stores.
www.ace.mmu.ac.uk /eae/Weather/Older/Convection.html   (224 words)

  
 Convection
Convection is the transfer of internal energy into or out of an object by the physical movement of a surrounding fluid that transfers the internal energy along with its mass.
Convection can arise spontaneously (or naturally or freely) through the creation of convection cells or can be forced by propelling the fluid across the object or by the object through the fluid.
Convection is the transfer of heat by the flow of a fluid.
hypertextbook.com /physics/thermal/convection   (548 words)

  
 Fixing a Convection Oven
A convection oven is a standard oven with a circulation fan to bake and roast food.
Hybrid ovens combine the advantages of both a convection oven and a microwave oven in one unit.
Convection ovens use a motor-driven circulating fan that's mounted between the unit's inner and outer housings.
www.bobvila.com /HowTo_Library/Fixing_a_Convection_Oven--F2134.html   (277 words)

  
 Convection: atmospheric motions in the vertical direction   (Site not responding. Last check: 2007-11-06)
In meteorology, convection refers primarily to atmospheric motions in the vertical direction.
As the earth is heated by the sun, different surfaces absorb different amounts of energy and convection may occur where the surface heats up very rapidly.
The bubble of relatively warm air that rises upward from the surface is called a "thermal".
ww2010.atmos.uiuc.edu /(Gh)/wwhlpr/hyd_convection.rxml?hret=/guides/mtr/cld/cldtyp/home.rxml&prv=1   (76 words)

  
 convection
Convection is a physical phenomenon of fluids that is seen in a variety of astronomical objects (Earth's interior and atmosphere, the Sun's interior, etc.).
It involves flow of a fluid (liquid or gas) that is caused by the presence of heat in the fluid.
Convection does not occur whenever there is a temperature gradient in a gas, however.
www.gpc.edu /~fbuls/ast101/part3/conv.htm   (191 words)

  
 Convection Theory in Heat Transfer
Generally, convection heat transfer can not be ignored when there is a significant fluid motion around the solid.
This is known as "natural convection" and it is a strong function of the temperature difference between the solid and the fluid.
Laminar flow generally occurs in relatively low velocities in a smooth laminar boundary layer over smooth small objects, while turbulent flow forms when the boundary layer is shedding or breaking due to higher velocities or rough geometries.
www.efunda.com /formulae/heat_transfer/convection/overview_conv.cfm   (164 words)

  
 convection — FactMonster.com
Thus, a current, called a convection current, becomes established in the fluid, with warmer, less dense fluid continually rising from the point of application of heat and cooler, denser portions of the fluid flowing outward and downward to replace the warmer fluid.
Convection currents are widely observed in both liquids and gases.
For example, when a portion of the atmosphere becomes heated by contact with a warm area of land, it rises into the cooler, higher altitudes, with the result that some of the moisture carried with it may be condensed to form clouds and precipitation.
www.factmonster.com /ce6/sci/A0813388.html   (364 words)

  
 NOAA - National Weather Service -
Convection occurring within an elevated layer, i.e., a layer in which the lowest portion is based above the earth's surface.
Elevated convection often occurs when air near the ground is relatively cool and stable, e.g., during periods of isentropic lift, when an unstable layer of air is present aloft.
Convection occurring within a surface-based layer, i.e., a layer in which the lowest portion is based at or very near the earth's surface.
www.weather.gov /glossary/index.php?word=convection   (357 words)

  
 Solar convection   (Site not responding. Last check: 2007-11-06)
The energy is moved towards the photosphere by convection (the green region in the top right corner of the diagram).
At this stage the large scale convective motion is no longer able to transport the heat from the cooker to the surface quickly enough and the milk starts to evaporate close to the bottom of the saucepan.
The solar convection zone moves energy in exactly the same way and the large scale motions at the solar surface contain a lot of energy that may be used indirectly to heat the corona.
www.sunblock99.org.uk /sb99/people/KGalsgaa/convect.html   (525 words)

  
 Convection   (Site not responding. Last check: 2007-11-06)
To produce a visual convection current in the classroom and compare it to the images taken of convection cells in the Sun.
Convection is the transport of energy due to density differences when not in a free-fall (microgravity) environment.
Convection motions within the solar interior generate magnetic fields that emerge at the surface as sunspots, and loops of hot gas called prominences.
sohowww.nascom.nasa.gov /explore/lessons/convection.html   (428 words)

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