Thermal radiation + Surfaces and radiation
- Thermal radiation is energy transfer by electromagnetical waves.
- All objects emit thermal radiaton.
- The hotter/more energy an object is the more energy it emits.
- Dark matt surfaces are better emitters of thermal radiation than light shiny surfaces.
- Dark matt surfaces are better absorbers of thermal radiation than light shiny surfaces.
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Conduction and Convection
- Conduction in a metal is due to mainly to free electrons inside the metal.
- Non-metals are generally poor conductors as they do not contain free electrons.
- Materials such as fiberglass are good insulators because they contain pockets of trapped air.
- Convection takes place only in fluids (liquids and gases)
- Heating a fluid makes it less dense.
- Convection is due to a hot liquid or gas rising.
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Heat transfer by design
- Small objects lose heat more easilly than large objects.
- Heat loss from a building can be reduced by using: aluminum foil behind radiators, cavity wall insulating, double/ triple glazing, loft insulation and under floor insulation.
- Example: radiators have a large surface area to disperse its heat quickly.
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