Heat transfer is a study of the exchange of thermal energy through a body or between bodies which occurs when there is a temperature difference. Heat can be transferred in 3 ways.

1) By Conduction : This is a transfer through solids. When you touch a hot object, the heat which you feel is transferred to your skin by conduction.

2) By Convection : It uses the motion of fluids to transfer heat. Convection can be Natural or Forced.

3) By Radiation : It does not require any medium to perform heat transfer. It is a heat transfer present in vacuum. It uses electromagnetic radiation (photons), which travels at the speed of light and is emitted by any matter with temperature above 0 degrees Kelvin (-273 °C).