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# Transfer of heat

## on Jun 15, 2012

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## Transfer of heatPresentation Transcript

• Transfer of HeatByJAVED IQBAL ANJUM PDT, AKU-IED, PDCNfor EDIP Project for Gorikote Cluster
• Flow of Presentation• Session Learning Outcomes• Transfer of Heat• Condition• Convection• Radiation• Expansion matter
• Session Learning Outcomes• By the end of this session C.Ps could be able to; • Develop their understanding regarding conduction, convection and radiation. • Demonstrate some experiments regarding conduction, convections, expansion in liquids and solids.
• Transfer of Heat• Heat can be transferred from place to place by conduction, convection and radiation. Dark matt surfaces are better at absorbing heat energy than light shiny surfaces. http://www.bbc.co.uk/schools/gcsebitesize/science/aqa_pre_2011/energy/heatrev1.s html• In the simplest of terms, the discipline of heat transfer is concerned with only two things: temperature, and the flow of heat. Temperature represents the amount of thermal energy available, whereas heat flow represents the movement of thermal energy from place to place.• http://www.efunda.com/formulae/heat_transfer/home/overview.cfm
• Cont…
• Conduction• Conduction is heat transfer by means of molecular agitation within a material without any motion of the material as a whole. If one end of a metal rod is at a higher temperature, then energy will be transferred down the rod toward the colder end because the higher speed particles will collide with the slower ones with a net transfer of energy to the slower ones.
• Convection• 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 above a hot surface occurs because hot air expands, becomes less dense, and rises. Hot water is likewise less dense than cold water and rises, causing convection currents which transport energy• Convection can also lead to circulation in a liquid, as in the heating of a pot of water over a flame. Heated water expands and becomes more buoyant. Cooler, more dense water near the surface descends and patterns of circulation can be formed, though they will not be as regular as suggested in the drawing http://hyperphysics.phy- astr.gsu.edu/hbase/thermo/heatra.html• .
• Radiation• Definition: Radiation is the emission and propagation of energy in the form of waves, rays or particles.• Examples:• A burning candle emits radiation in the form of heat and light. Electrons dropping from one energy state to a lower state emit radiation in the form of a photon.• http://chemistry.about.com/od/chemistryglossary/g/Radiation-Definition.htm
• Expansion in matters• Solids, Liquids and gases expand when they are heated. This is because the particles in liquids and gases move faster when they are heated than they do when they are cold. As a result, the particles take up more volume. This is because the gap between particles widens, while the particles themselves stay the same size.• The liquid or gas in hot areas is less dense than the liquid or gas in cold areas, so it rises into the cold areas. The denser cold liquid or gas falls into the warm areas. In this way, convection currents that transfer heat from place to place are set up.
• Food for thought• Science is a first-rate piece of furniture for a mans upper chamber, if he has common sense on the ground floor.• Oliver Wendell Holmes (1809-1894) The Poet at the Breakfast-Table, 1872 Chapter 5