Convection , mechanism of heat transfer

Convection :

- Convection is usually the dominant form of  heat transfer in liquid and gases  .

- heat flow is archived by actual mixing of warmer portion with the cooler portion of the same material .

-  When a fluid is heated the region is closest to contact with the heat source become less dense due to increased kinetic energy in the particle  .

-  the Portion of the fluid that is less dense then risks , while the denser portion of the fluid sinks .

-  This motion in fluid causes the transfer of energy .

- Convection heat  transfer is essentiallly the transfer of heat via mass transfer and it involved the combined effect of conduction and fluid motion .

Types :

1. Natural Convection :

 

it is the fluid motion caused by the buoyancy forces that are induced by density  differences due to the vibration of temperature in the fluid  .

Example  : - Boiling water .

2 Forced convection :

In this case the fluid is forced to flow by a use of pump fan or other mechanical means  .