PPT: Forced Convective Heat Transfer | Heat Transfer - Mechanical Engineering PDF Download

 Page 1


Introduction
• Convection The process of heat transfer
between a solid surface & the fluid in motion.
• Natural Fluid moves due to density diff.
caused by HT between solid & liquid.
• Forced Fluid motion is imparted by
external means. i.e. pump,fan,slope etc.
Page 2


Introduction
• Convection The process of heat transfer
between a solid surface & the fluid in motion.
• Natural Fluid moves due to density diff.
caused by HT between solid & liquid.
• Forced Fluid motion is imparted by
external means. i.e. pump,fan,slope etc.
Mechanism of Forced Convection
• Convection heat transfer is complicated since
it involves fluid motion & heat conduction.
• The fluid motion enhances heat transfer.
• The rate of convection heat transfer is
expressed by New ton’ s law of cooling:
Page 3


Introduction
• Convection The process of heat transfer
between a solid surface & the fluid in motion.
• Natural Fluid moves due to density diff.
caused by HT between solid & liquid.
• Forced Fluid motion is imparted by
external means. i.e. pump,fan,slope etc.
Mechanism of Forced Convection
• Convection heat transfer is complicated since
it involves fluid motion & heat conduction.
• The fluid motion enhances heat transfer.
• The rate of convection heat transfer is
expressed by New ton’ s law of cooling:
• The convective heat transfer coefficient h
strongly depends on the fluid properties and
roughness of the solid surface, and the type of
the fluid flow.
Page 4


Introduction
• Convection The process of heat transfer
between a solid surface & the fluid in motion.
• Natural Fluid moves due to density diff.
caused by HT between solid & liquid.
• Forced Fluid motion is imparted by
external means. i.e. pump,fan,slope etc.
Mechanism of Forced Convection
• Convection heat transfer is complicated since
it involves fluid motion & heat conduction.
• The fluid motion enhances heat transfer.
• The rate of convection heat transfer is
expressed by New ton’ s law of cooling:
• The convective heat transfer coefficient h
strongly depends on the fluid properties and
roughness of the solid surface, and the type of
the fluid flow.
fig. Forced convection
• It is assumed that the velocity of the fluid is
zero at the wall, this assumption is called
no-slip condition.
Page 5


Introduction
• Convection The process of heat transfer
between a solid surface & the fluid in motion.
• Natural Fluid moves due to density diff.
caused by HT between solid & liquid.
• Forced Fluid motion is imparted by
external means. i.e. pump,fan,slope etc.
Mechanism of Forced Convection
• Convection heat transfer is complicated since
it involves fluid motion & heat conduction.
• The fluid motion enhances heat transfer.
• The rate of convection heat transfer is
expressed by New ton’ s law of cooling:
• The convective heat transfer coefficient h
strongly depends on the fluid properties and
roughness of the solid surface, and the type of
the fluid flow.
fig. Forced convection
• It is assumed that the velocity of the fluid is
zero at the wall, this assumption is called
no-slip condition.
• As a result, the heat transfer from the solid
surface to the fluid layer adjacent to the
surface is by pure conduction, since the fluid is
motionless.
• Thus h in general, varies along the flow
direction.
• The mean or average convection heat transfer
coefficient for a surface is determined by
(properly) averaging the local heat transfer
coefficient over the entire surface.