Thermal energy transfer

Conduction is a process where heat is transferred within a material or to another material in direct contact.
It works by the increase of kinetic energy in atoms or molecules, causing them to vibrate more and pass energy to neighboring particles.
In a solid, this process is more effective because particles are closer together. Metals are efficient conductors due to their free electrons which can move energy quickly.

Convection happens in fluids (gases and liquids), where warmer, less dense regions rise, and cooler, denser regions sink.
This creates a convection current that circulates the fluid and distributes heat. This is the principle behind radiators or boiling water.
Essentially, heat is transferred by the movement of mass from one place to another.

Radiation is the transfer of heat without requiring solids, liquids, or gases.
All objects emit and absorb infrared radiation, with hotter objects radiating more. The transfer of heat via radiation does not require a material medium and can happen across a vacuum, like space.
Significant factors of radiation include the nature of the material’s surface: dark, matt surfaces are good absorbers and good emitters, while light, shiny surfaces are poor absorbers and poor emitters, but good reflectors of radiation.

Insulation is used to reduce heat transfer by conduction, convection, and radiation.
Insulating materials contain trapped air spaces, which minimises heat transfer by conduction. Furthermore, the material prevents convection currents.
Surfaces that are poor radiators can be used to reduce heat loss by radiation. Examples include shiny aluminium foil often used behind radiators or in loft spaces.
The aim is to reduce wasted energy in the form of heat loss, improving the efficiency of the energy transfer.