Thermodynamics HW Solutions 627

Thermodynamics HW Solutions 627 - Chapter 7 External Forced...

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Chapter 7 External Forced Convection 7-97 A spherical tank used to store iced water is subjected to winds. The rate of heat transfer to the iced water and the amount of ice that melts during a 24-h period are to be determined. Assumptions 1 Steady operating conditions exist. 2 Air is an ideal gas with constant properties. 7 The pressure of air is 1 atm. Properties The properties of air at 1 atm pressure and the free stream temperature of 30 ° C are (Table A-15) kg/m.s 10 872 . 1 /s m 10 608 . 1 C W/m. 02588 . 0 5 2 5 - × = × = ° = μ υ k 7282 . 0 Pr kg/m.s 10 729 . 1 5 C 0 @ , = × = ° s Analysis ( a ) The Reynolds number is [] 6 2 5 10 304 . 1 /s m 10 608 . 1 m) (3.02 m/s 1000/3600) (25 Re × = × × = υ = D V The Nusselt number corresponding to this Reynolds number is determined from 1056 10 729 . 1 10 872 . 1 ) 7282 . 0 ( ) 10 304 . 1 ( 06 . 0 ) 10 304 . 1 ( 4 . 0 2 Pr Re 06 . 0 Re 4 . 0 2 4 / 1 5 5 4 . 0 3 / 2 6 5 . 0 6 4 / 1 4 . 0 3 / 2 5 . 0 = × × × + × + = μ μ + + = = s k hD Nu and C . W/m 05 . 9 ) 1056 ( m 02 . 3 C W/m. 02588 . 0 2 ° = ° = = Nu D k h In steady operation, heat transfer through the tank by conduction is equal to the heat transfer from the outer surface of the tank by convection and radiation. Therefore, && & & () ( ,, QQ Q Q TT R hA T T A T T s out s in sphere o o surr s out
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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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