The Thermal Boundary Layer

The Thermal Boundary Layer - The Thermal Boundary Layer The...

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The Thermal Boundary Layer The thermal boundary layer is the thin region of wall-adjacent viscous flow in which temperature gradients exist. Consider T s = Constant. Then, the thickness of the thermal boundary- layer is the normal distance from the surface to the location where s s TT 0.99 ⎛⎞ θ= = ⎜⎟ ⎝⎠ , i.e., s th th 0.99 s y0 . 9 9 , i . e . , y δ= = . (1) At the surface, there is no fluid motion. Therefore, at the surface, energy transfer occurs due to conduction, so that 0 y f ' ' s y T k q = = Fourier’s law of heat conduction (2) Then, ) T T ( y T k h s 0 y f = = , when combined with Newton’s Law of Cooling. (3) For 2-D, incompressible, constant-property, non-reacting fluid flow with negligible body forces and no energy generation, the energy equation is q y T k y x T k x y T v x T u C p ± + Φ μ + + = + ρ (4) Φ Viscous dissipation - rate at which mechanical energy is irreversibly converted to thermal energy; this term is important only in high-viscosity flow and high-speed flow.

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This note was uploaded on 10/13/2010 for the course MECH 414 taught by Professor Ghia during the Winter '06 term at University of Cincinnati.

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The Thermal Boundary Layer - The Thermal Boundary Layer The...

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