Thermodynamics HW Solutions 592

Thermodynamics HW Solutions 592 - . ( ) 658 , 806 ( 06 . )...

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Chapter 7 External Forced Convection 7-60 Air flows over a spherical tank containing iced water. The rate of heat transfer to the tank and the rate at which ice melts are to be determined. Assumptions 1 Steady operating conditions exist. 2 Radiation effects are negligible. 3 Air is an ideal gas with constant properties. 4 The local atmospheric pressure is 1 atm. Properties The properties of air at 1 atm pressure and the free stream temperature of 25 ° C are (Table A-15) 7296 . 0 Pr kg/m.s 10 729 . 1 kg/m.s 10 849 . 1 /s m 10 562 . 1 C W/m. 02551 . 0 5 C 0 @ , 5 2 5 - = × = × = × = ° = ° s k μ υ Air V = 7 m/s T =25 ° C Iced water 0 ° C D = 1.8 m Analysis The Reynolds number is 658 , 806 /s m 10 562 . 1 m) m/s)(1.8 (7 Re 2 5 = × = υ = D V The proper relation for Nusselt number corresponding to this Reynolds number is [] [] 1 . 790 10 729 . 1 10 849 . 1 ) 7296
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Unformatted text preview: . ( ) 658 , 806 ( 06 . ) 658 , 806 ( 4 . 2 Pr Re 06 . Re 4 . 2 4 / 1 5 5 4 . 3 / 2 5 . 4 / 1 4 . 3 / 2 5 . = + + = + + = = s k hD Nu The heat transfer coefficient is C . W/m .20 11 ) 1 . 790 ( m 8 . 1 C W/m. 02551 . 2 = = = Nu D k h Then the rate of heat transfer is determined to be W 2850 = = = = = C ) 25 )( m C)(10.18 . W/m 20 . 11 ( ) ( m 10.18 = m) 8 . 1 ( 2 2 2 2 2 T T hA Q D A s s s & The rate at which ice melts is kg/min 0.512 = = = = kg/s 00854 . kJ/kg) 7 . 333 ( = kW 850 . 2 m m h m Q fg & & & & 7-47...
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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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