# Lecture 5 - 1 MECE 4364 Heat Transfer Prof Dong Liu Department of Mechanical Engineering University of Houston Lecture 5 Sep 7 2010 Lecture 5 2

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MECE 4364 Heat Transfer Prof. Dong Liu Department of Mechanical Engineering University of Houston 1 Lecture 5 – Sep 7, 2010 Lecture 5 Conduction 2

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Lecture 5 Thermal Circuits: Plane Wall R tot = 1 h 1 A + L kA + 1 h 2 A 3 ,1 ,2 total x TT T R qq ∞∞ Δ == 14 11 ABC tot LLL R hA k A k A k A hA =++ + + R tot = L E k E A + k F A 2 L F + k G A 2 L G 1 + L H k H A Lecture 5 Tube Wall Solution: Heat flux: Heat flow: T ( r ) = T s T s ,2 ln r 1 r 2 () ln r r s + T s ,2 q r =− k dT dr = kT s T s ,2 ( ) r ln r 2 r 1 q r kA dT dr = 2 π rL q r = 2 Lk T s T s ,2 ln r 2 r 1 4 Conduction thermal resistance: ( compare to plane wall ) Overall thermal resistance: ( dependence on r 1 and r 2 ? )
Lecture 5 Composite Tube Wall () ,1 ,4 ,4 21 32 43 11 4 4 ln ln ln 22 2 2 2 r tot ABC TT q rr R hr L k L k L k L L ππ π ∞∞ == ++++ ( ) 44 ln ln 1 2 ln 1 tot AB C R L k L k L kL h rL =+ + ++ 5 ,4 ,4 r tot qU A T T R Define the overall heat transfer coefficient Lecture 5 Spherical Shell Solution: Heat Flux: Heat Flow: T ( r ) = T s T s T s ,2 1 r 1 r ( ) 1

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## This note was uploaded on 01/27/2011 for the course MECE 4364 taught by Professor Lipinglui during the Winter '10 term at University of Houston.

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Lecture 5 - 1 MECE 4364 Heat Transfer Prof Dong Liu Department of Mechanical Engineering University of Houston Lecture 5 Sep 7 2010 Lecture 5 2

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