Convection Slideshare.

1. CONVECTION
BY: SRIJAN, AM, PHU AND AZAR

2. DEFINITION
• Convection – The transfer of heat energy by-
1. The movement of fluids (liquids or gas)
2. Convection currents due to hot fluid rising and cold fluid sinking
• Convection can arise spontaneously through the creation of convection cells,
or can be forced by propelling the fluid across the object or by the object
through the fluid.

3. HEAT TRANSFER BY CONVECTION
• Convection is heat transfer by mass motion of a fluid, such as air or water when the heated fluid moves
away from the source of heat, carrying energy with it. Convection above a hot surface occurs because
hot air expands, becomes less dense, and rises.
• Convection can be –
• forced or assisted convection - Forced convection occurs when a fluid flow is induced by an external
force, such as a pump, fan or a mixer.
• natural or free convection –
• Natural convection is caused by forces due to density differences caused by temperature variations in
the fluid. At heating, the density change will cause the fluid to rise and be replaced by cooler fluid that
also will heat and rise.