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CONVECTION INTRODUCTION, image, image -->, image, The region of the…
CONVECTION INTRODUCTION
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THE NUSSELT NUMBER
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Represent the enhancement of heat transfer through a fluid layer as a result of convection relative to conduction across the same fluid layer.
VELOCITY BOUNDARY LAYER
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The hypothetical line of u= 0.99V divides the flow over a plate into 2 regions:
(a) the boundary layer region
(b) the irrotational flow region
THERMAL BOUNDARY LAYER
The thermal boundary layer: the flow region over the surface in which the temperature variation in the direction normal to the surface is significant
Thermal boundary layer develops when a fluid at a specified temperature flows over a surface that is at a different temperature
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The convection heat transfer rate anywhere along the surface is directly related to the temperature gradient at the location.
THE PRANDTL NUMBER
The relative thickness of the velocity and the thermal boundary layers is described by Prandtl number
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The thermal boundary layer is much thicker for liquid metals and much thinner for oils relative to the velocity boundary layer
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