Thermodynamics HW Solutions 588

Thermodynamics HW Solutions 588 - Chapter 7 External Forced...

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Chapter 7 External Forced Convection 7-58 A cylindrical hot water tank is exposed to windy air. The temperature of the tank after a 45-min cooling period is to be estimated. Assumptions 1 Steady operating conditions exist. 2 Radiation effects are negligible. 3 Air is an ideal gas with constant properties. 4 The surface of the tank is at the same temperature as the water temperature. 5 The heat transfer coefficient on the top and bottom surfaces is the same as that on the side surfaces. Properties The properties of water at 80 ° C are (Table A-9) C J/kg. 4197 kg/m 8 . 971 3 ° = = p C ρ The properties of air at 1 atm and at the anticipated film temperature of 50 ° C are (Table A-15) 7228 . 0 Pr /s m 10 798 . 1 C W/m. 02735 . 0 2 5 - = × = ° = υ k Analysis The Reynolds number is 015 , 309 /s m 10 798 . 1 m) (0.50 m/s 3600 1000 40 Re 2 5 = × × = υ = D V The proper relation for Nusselt number corresponding to this Reynolds number is () [] () [] 9 . 484
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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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