Heat exchangers are a device that exchange the heat between two fluids of different
temperatures that are separated by a solid wall. The temperature gradient, or the differences in
temperature facilitate this transfer of heat. Transfer of heat happens by three principle means:
radiation, conduction and convection. In the use of heat exchangers radiation does take place.
However, in comparison to conduction and convection, radiation does not play a major role.
Conduction occurs as the heat from the higher temperature fluid passes through the solid wall.
To maximize the heat transfer, the wall should be thin and made of a very conductive material.
The biggest contribution to heat transfer in a heat exchanger is made through convection.