Thermodynamics HW Solutions 658

Thermodynamics HW Solutions 658 - Chapter 8 Internal Forced...

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Chapter 8 Internal Forced Convection 8-45 Laminar flow of a fluid through an isothermal square channel is considered. The change in the pressure drop and the rate of heat transfer are to be determined when the mean velocity is doubled. Analysis The pressure drop of the fluid for laminar flow is expressed as Δ Pf L D L DD L D L D mm m m m 1 22 2 2 2 64 2 64 2 32 == = = ρρ υ ρ υρ VV V V V Re When the free-stream velocity of the fluid is doubled, the pressure drop becomes Δ L D L L D L D m m m 2 2 2 2 2 64 4 2 64 2 4 2 64 = = υ ρ () Re V V V Laminar flow V m L Their ratio is Δ Δ P P 2 1 64 32 2 The rate of heat transfer between the fluid and the walls of the channel is expressed as ln 4 . 0 3 / 1 3 / 1 3 / 1 3 / 1 ln 4 . 0 3 / 1 ln ln 1 Pr Re 86 . 1 Pr Re 86 . 1 T A L D D k D T A L D D k T NuA D k T hA Q s b m s b Δ
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This note was uploaded on 01/22/2012 for the course PHY 4803 taught by Professor Dr.danielarenas during the Fall '10 term at UNF.

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