How Does Heat Transfer Occur?

Ever wonder how does your hands feel warm after you hold the steaming cup of coffee for a while? The phenomenon of heat transfer is the secret behind this occurrence.

The process of transferring heat from one medium to other or from one object to another is called heat transfer. Het transfer may occur by one or more of the three basic mechanism-

1.Conduction
2.Convection
3.Radiation

Let us discuss all the three basic mechanisms of heat transfer in brief.

Conduction

In conduction, heat is conducted through solids, liquids, and gases. The heat is propogated by the transfer of energy of motion between the adjacent molecules. In a gas, the hotter molecules which have greater energy and motions impart energy to the adjacent molecules at the lower energy levels. This type of transfer is present to some extent in all solids, liquids or gases in which a temperature gradient exists. In conduction, energy is also be transferred by free electrons which is important in metallic solids.

Example- heat transfer through walls of exchanges or a refrigerator, freezing of ground during the winter.