Heat Transfer

Heat Transfer

Heat energy can be transferred in three different ways:
1. Radiation
  1. Emitted by solids, liquids and gases
  2. An object that is hotter than its surroundings emits more than it absorbs
  3. Radiation depends on surface colour and texture
    1. Dark, matt surfaces:
      1. Absorb infrared radiation better
      2. Emit much more
    2. Light, shiny surfaces:
      1. Reflect more infrared radiation
2. Conduction
  1. Mainly occurs in solids
  2. CONDUCTION OF HEAT ENERGY IS WHERE VIBRATING PARTICLES PASS ON THEIR EXTRA KINETIC ENERGY TO NEIGHBOURING PARTICLES
  3. Metals are good conductors due to their free electrons
    1. The electrons can move freely meaning that it is a much faster way of transferring energy
3. Convection
  1. Only occurs in liquids and gases
    1. Can't happen in solids because the particles can't move
    2. Other processes that only happen in liquids and gases:
      1. Condensation
        This is when gas turns into a liquid
        If the temperature gets cold enough and the particles get close enough condensation takes place
      2. Evaporation
        This is when a liquid turns into a gas
        The particles with the most kinetic energy are most likely to evaporate
  2. CONVECTION OCCURS WHEN THE MORE ENERGETIC PARTICLES MOVE FROM THE HOTTER REGION TO THE COOLER REGION- AND TAKE THE HEAT WITH THEM
  3. Convection currents are all about changes in DENSITY
    1. Heating a room with a radiator relies on convection currents
      1. Hot, less dense air near the radiator rises and so denser, cooler air flows to replace it
By Stephen Thompson

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