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Convection Heat TransferInstructor: M.H.Saidi
PhD, Professor
School of Mechanical Engineering
Sharif University of Technology
Fall 2011
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Lecture #4
Convection Heat Transfer
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Convection Heat Transfer
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:Summary of second session
vScale Analysis
vIntroduction to boundary layer flow
vThis session: Laminar Boundary Layer Flow(Velocity and Temperature fields)
Convection Heat Transfer
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LAMINAR BOUNDARY LAYER FLOW
CONCEPT OF BOUNDARY LAYER
In the d L region, then, the longitudinal momentumequation (8) accounts for the competition between three typesof forces:
From the mass continuity equation, we have:
Convection Heat Transfer
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LAMINAR BOUNDARY LAYER FLOW
CONCEPT OF BOUNDARY LAYER
If the boundary layer region d L is slender(not Bluff), suchthat:
The last scale in Eq. (14) is the scale most representative of thefriction force. Neglecting the term at the expense of the
term in the x momentum Equation (8) yields:
Similarly the y momentum equation reduces to:
2 2/U x∂ ∂2 2/U y∂ ∂
Convection Heat Transfer
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LAMINAR BOUNDARY LAYER FLOW
CONCEPT OF BOUNDARY LAYER
Convection Heat Transfer
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LAMINAR BOUNDARY LAYER FLOW
CONCEPT OF BOUNDARY LAYER
Convection Heat Transfer
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LAMINAR BOUNDARY LAYER FLOW
CONCEPT OF BOUNDARY LAYER
Convection Heat Transfer
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LAMINAR BOUNDARY LAYER FLOW
VELOCITY AND THERMAL BOUNDARY LAYERS
Convection Heat Transfer
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LAMINAR BOUNDARY LAYER FLOW
VELOCITY AND THERMAL BOUNDARY LAYERS
Convection Heat Transfer
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LAMINAR BOUNDARY LAYER FLOW
VELOCITY AND THERMAL BOUNDARY LAYERS
1/ 2Re 1L >>
2/( / 2)fC vτ ρ=
Convection Heat Transfer
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LAMINAR BOUNDARY LAYER FLOW
VELOCITY AND THERMAL BOUNDARY LAYERS
Convection Heat Transfer
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LAMINAR BOUNDARY LAYER FLOW
VELOCITY AND THERMAL BOUNDARY LAYERS
Tδ δ<<Tδ δ>>
Convection Heat Transfer
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LAMINAR BOUNDARY LAYER FLOW
VELOCITY AND THERMAL BOUNDARY LAYERS
Tδ δ>>
1<<
>>
Convection Heat Transfer
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LAMINAR BOUNDARY LAYER FLOW
VELOCITY AND THERMAL BOUNDARY LAYERS
Tδ δ>>
Tδ δ
Convection Heat Transfer
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LAMINAR BOUNDARY LAYER FLOW
VELOCITY AND THERMAL BOUNDARY LAYERS
Tδ δ>>
Tδ δ>> 1/ 2 1Pr <<
Convection Heat Transfer
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LAMINAR BOUNDARY LAYER FLOW
VELOCITY AND THERMAL BOUNDARY LAYERS
Tδ δ<<
:
Convection Heat Transfer
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LAMINAR BOUNDARY LAYER FLOW
VELOCITY AND THERMAL BOUNDARY LAYERS
Tδ δ<<
Tδ δ<< 1/ 3 1Pr >>
Convection Heat Transfer
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LAMINAR BOUNDARY LAYER FLOW
Concept of Reynolds number
Convection Heat Transfer
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:Next session
vLaminar Boundary Layer Flow: Integral Solution