HEAT AND MASS TRANSFER (SEMESTER + GATE)

1. Heat:-

it is the form of energy that is transferred between two substances at different temperatures.

2.Difference between thermodynamics and heat transfer:-

In thermodynamics we deals with system in equilibrium i.e to bring a system from one equilibrium state to another equilibrium state ;how much heat is require is the criteria in TD analysis.

 

But in heat transfer analysis we calculate at what rate the change of state occurs by calculating the rate of heat transfer.

unit of heat in TD is jule but in HMT is watt.

3.Modes of heat transfer:-

i.conduction

ii.convection

iii.radition

i. Conduction:-

Conduction is a mode of heat transfer which generally occurs in solid due to temperature difference.

Associated with molecular lattice vibration energy transfer (30%) and also by free electron transfer (70%).

The reason behind all electrical good conductors are also in generally good conductor of heat is that the presence of abudant free electron.

EXAMPLE: All metals.

NOTE:

Exception to the above statement is diamond( a non metal)

The highest thermal conductivity of diamond is due to its perfect crystalline molecular lattice arrangement.