Heat Transfer

Heat Transfer

Surface & Radiation
1. Every object EMITS thermal radiation
  1. Dark, matt surfaces emit more radiation than light , shiny surfaces
    1. DARK MATT SURFACES
      1. BETTER: absorbing radiation than light and shiny surfaces.
        BECAUSE *has lots of cavities - which trap and absorb the radiation
Conduction & Convection
1. Metals conduct better than non metals
  1. BECAUSE * They contain FREE ELECTIONS, which move around randomly inside the metal and they hold positive ions together.They collide with each other and with the positive ions.
    1. IONS are charged particles
    2. EXAMPLE: a rod being heated, free electrons on the hot end gain kinetic energy and more faster.The electrons then 'Defuse'/spread out and collide with other free electrons = They transfer kinetic energy to there electrons and ions = energy transfer has occured
2. Convection ONLY takes place in Fluids (gases or liquids)
  1. EXAMPLE: hot water tank, hot water from the boiler rises and flows into the tank where it rises to the top.
  2. Takes place due to CIRCULATION CURRENTS in the fluid
3. Conduction ONLY takes place in Solids
Artificially modifying heat transfer at home
1. Roof 25% Windows 10% Doors 15% Walls 35% Floor 15%
  1. Sometimes we need o control heat transfer, for example , a car engine which overheats could go up in flames.

Resource summary

	Created by sanakaka2 over 11 years ago