P1b: Keeping Homes Warm

Practical Insulation
1. Double glazing reduces energy loss by conduction. The gap between the two pieces of glass is filled with a gas or contains a vacuum
  1. Particle in a gas are far apart. It is very difficult to transfer energy. There are no particles in a vacuum so it is impossible to transfer energy by conduction
2. Loft Insulation reduces energy loss by conduction and convection
  1. Warm air in the home rises
    1. Energy is transferred through the ceilling by conduction
      1. Air in the loft is warmed by the top of the ceiling and is trapped in the loft insulation
        Both sides of the ceiling are at the same temperature so no energy is lost
        Without loft insulation, the warm air in the loft can move by convection and heat the roof tiles
        Energy is transferred to the outside by conduction
3. Cavity Wall insulation reduces energy loss by convection and conduction
  1. The air in the foam is a good insulator
  2. the air cannot move by convection because it is trapped in the foam
4. Insulation blocks used to build new home have shiny foil on both sides to reduce energy transfer by radiation
  1. energy from the sun is reflected back to keep the home cool in the summer
  2. energy from the home is reflected back in the winter
Conduction, Convection and Radiation
1. Energy can be transferred by:
  1. Conduction - due to the transfer of Kinetic Energy
  2. Convection - a gas expands when it is heated. This make its less dense so it rises
  3. Radiation does not need a material to transfer energy. It can be done by a vacuum
Energy Efficency
1. Energy Transformations can be shown in Sankey Diagrams
  1. Energy from the source can be lost to the sink
  2. Different types of insulation cost different prices
  3. Everything that transfers energy will waste some of the energy as heat to the surroundings

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	Criado por antonia_f quase 10 anos atrás