HEAT AND MASS TRANSFER

The transfer of energy is always from the higher temperature medium to the lower temperature

one. The energy transfer stops when the two mediums reach the same temperature. Heat is the

form of energy that can be transferred from one system to another as a result of temperature

difference. The science that deals with rate of such energy transfer is heat transfer.

Thermodynamics deals with the amount of heat transfer without indicating how long the process

will take. Heat transfer deals with determining the rate of heat transfer to or from a system,

which is the times of heating and cooling. Thermodynamics deals with equilibrium states and

changes from one equilibrium state to another. Heat transfer deals with nonequilibrium systems.

The basic requirement for heat transfer is the presence of a temperature difference, also known as

a driving force. The direction depends on the magnitude of the temperature gradient, the

temperature difference per unit length or the rate of change of temperature. The larger the

temperature gradient, the higher the rate of heat transfer.