3.2 Thermal conductivity values of materials and applications of thermal energy transfer science

All materials conduct heat energy to a greater or lesser degree.

The thermal conductivity of a material is a measure of how efficiently heat is transferred through a material by conduction.

Materials like metals are very good heat conductors and transfer thermal energy very quickly.

Materials like stone, brick, wood and concrete etc. are poor heat conductors and have low thermal conductivities - therefore can be used as good thermal insulation materials.

Thermal conductivity data is particularly important when considering the material required to fulfil a particular application e.g. in heating systems when in one situation you might want good insulation and in another rapid heat transfer.

Clothes and blankets trap pockets of air.

Air is a poor conductor of thermal energy, so the trapped air provides an effective layer of insulation.

Materials like wool fibres, which is also a poor thermal energy conductor, trap the air giving a very effective layer of thermal insulation.

Also, because of the porous nature of the material, little of your body heat is conveyed away by convection.

 

Other material situations

Getting your 'fish and chips' served in layers of paper keeps the food hot because paper is a poor conductor of heat.

Also, if you want to keep your freshly bought ice cream as cool as possible on returning from the supermarket, you can wrap it is old newspaper - which can still be recycled.

See also Part 3.3 Heating and insulating buildings to minimise waste energy e.g. in the home