heat transfer
- Created by: helen
- Created on: 13-01-13 18:14
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- heat transfer
- thermal radiation = infra-red radiation.
- dark matt surfaces emit more radiation then shiny light ones.
- they also absorb radiation better.
- shiny, light surfaces reflect radiation the best.
- conduction: free electrons are given where heated and diffused- this energy is passed on as electrons collide.
- a conductor can pass on energy quicker.
- convection occurs with only liquids or gases.
- Hot, light air rises, whilst cold, dense air sinks. This causes convectioncurrent in gases and liquids.
- fluids expand when heated making them lighter
- Hot, light air rises, whilst cold, dense air sinks. This causes convectioncurrent in gases and liquids.
- vacuum cuts out heat transfer by conduction and convection.
- glass is a poor conductor so little heat conducted here.
- glass surfaces are silvery to reduce radiation from outer wall.
- double glazed windows with vacuum reduces conduction.
- cavity wall insulates reducing heat loss
- loft insulation reduces heat loss through roof.
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