6. Physical Mechanism of Convection
Convection heat transfer strongly depends on
• dynamic viscosity,
• thermal conductivity,
• density
• specific heat
• fluid velocity
• geometry
• the roughness of the solid surface,
• type of fluid flow
The convection heat transfer coefficient h can be
defined as the rate of heat transfer between a solid
surface and a fluid per unit surface area per unit
temperature difference.
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8. Nusselt Number
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= 1 for a fluid
Nusselt number represents the enhancement of
heat transfer through a fluid layer as a result of
convection relative to conduction across the
same fluid layer.
The larger the Nusselt number, the more
effective the convection.
A Nusselt number of Nu
layer represents heat transfer across the layer by
pure conduction.
Bi = ?
9. Classification of Fluid Flows
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Viscous versus Inviscid Flow
Flows in which the effects of viscosity are significant are called viscous flows.
The effects of viscosity are very small in some flows, and neglecting those effects greatly
simplifies the analysis without much loss in accuracy. Such idealized flows of zero-
viscosity fluids are called frictionless or inviscid flows.
10. Classification of Fluid Flows
Internal versus External Flow
The flow of an unbounded fluid over a surface such as a plate, a wire, or a pipe is external
flow.
The flow in a pipe or duct is internal flow if the fluid is completely bounded by solid
surfaces.
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11. I want to thank
Dr Ajay Semalty
H.N.B. Garhwal University (A Central University) Srinagar Garhwal (Uttarakhand)
for introducing Academic writing course. This course is beneficial for researchers
and academicians. I learn so many new things from this course. I sincerely pay my
gratitude to Prof Semalty.
