Thermodynamics HW Solutions 555

Thermodynamics HW Solutions 555 - Chapter 7 External Forced...

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Chapter 7 External Forced Convection 7-25 Laminar flow of a fluid over a flat plate is considered. The change in the drag force and the rate of heat transfer are to be determined when the free-stream velocity of the fluid is doubled. Analysis For the laminar flow of a fluid over a flat plate maintained at a constant temperature the drag force is given by 5 . 0 5 . 0 2 / 3 2 5 . 0 1 2 5 . 0 1 5 . 0 2 1 664 . 0 2 328 . 1 get we lation, number re Reynolds ng Substituti 2 Re 328 . 1 Therefore Re 328 . 1 where 2 L A A L F A F C A C F s s D s D f s f D υ ρ = = = = = V V V V V V L When the free-stream velocity of the fluid is doubled, the new value of the drag force on the plate becomes 5 . 0 5 . 0 2 / 3 2 5 . 0 2 ) 2 ( 664 . 0 2 ) 2 ( ) 2 ( 328 . 1 L A A L F s s D = = V V V The ratio of drag forces corresponding to and 2 is V V F F V V D D 2 2 32 2 == () / / 2 3/2 We repeat similar calculations for heat transfer rate ratio corresponding to
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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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