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Thermal Insulation

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Introduction

Jonathan Mabanta 10N

Thermal Insulation

Scientific knowledge

Thermal insulation is the method of preventing heat from escaping a container or from entering the container. In other words, thermal insulation can keep an enclosed area such as a building warm, or it can keep the inside of a container cold. Heat is transferred by from one material to another by conduction, convection and/or radiation. Insulators are used to minimize that transfer of heat energy. In home insulation, the R-value is an indication of how well a material insulates.

Conduction
Heat energy can move through a substance by conduction. Metals are good conductors of heat, but non-metals and gases are usually poor conductors of heat. Poor conductors of heat are called insulators. Heat energy is conducted from the hot
end of an object to the cold end.Metals consist of metal ions (charged particles formed when the metal atoms lose electrons) packed closely together. Metals have free electrons that can move through the structure of the metal. This is why metals are good conductors of electricity.

Convection
Liquids and gases are fluids.

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Middle

  • If the air outside is cold, you may want to protect your skin by wearing clothes that keep the cold out and the body warmth in.
  • If your house has cool air inside during the summer, you may want to prevent the temperature from becoming the same as the hot air outside by having the house well insulated.
  • If you have a hot drink, you may want to prevent it from becoming room temperature by putting it in a thermos bottle.

How insulation works?

Insulation is a barrier that minimizes the transfer of heat energy from one material to another by reducing the conduction, convection and/or radiation effects.

Insulation from conduction

Conduction occurs when materials--especially solids--are in direct contact with each other. High kinetic energy atoms and molecules bump into their neighbours, increasing the neighbour’s energy. This increase in energy can flow through materials and from one material to another.

Solid to solid

To slow down the transfer of heat by conduction from one solid to another, materials that are poor conductors are placed in between the solids. Examples include:

  • Fibreglass is not a good conductor nor is air. That is why bundles of loosely packed fibreglass strands are often used as insulation between the outer and inner walls of a house.
  • Heat cannot travel though a vacuum. That is why a thermos bottle has an evacuated lining. Heat cannot be transferred from one layer to the other through the thermos bottle vacuum.
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Conclusion

Reducing heat loss

Heat energy is transferred from homes by conduction through the walls, floor, roof and windows. It is also transferred from homes by convection. For example, cold air can enter the house through gaps in doors and windows, and convection currents can transfer heat energy in the loft to the roof tiles. Heat energy also leaves the house by radiation through the walls, roof and windows.

Ways to reduce heat loss.
There are some simple ways to reduce heat loss, including fitting carpets, curtains and draught excluders.

Heat loss through windows can be reduced using double glazing. There may be air or a vacuum between the two panes of glass. Air is a poor conductor of heat, while a vacuum can only transfer heat energy by radiation.

Heat loss through walls can be reduced using cavity wall insulation. This involves blowing insulating material into the gap between the brick and the inside wall, which reduces the heat loss by conduction. The material also prevents air circulating inside the cavity, therefore reducing heat loss by convection.

Heat loss through the roof can be reduced by laying loft insulation. This works in a similar way to cavity wall insulation.

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