Thermodynamics HW Solutions 712

Thermodynamics HW Solutions 712 - Chapter 9 Natural...

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Unformatted text preview: Chapter 9 Natural Convection 9-22 Water is boiling in a pan that is placed on top of a stove. The rate of heat loss from the cylindrical side surface of the pan by natural convection and radiation and the ratio of heat lost from the side surfaces of the pan to that by the evaporation of water are to be determined. Assumptions 1 Steady operating conditions exist. 2 Air is an ideal gas with constant properties. 3 The local atmospheric pressure is 1 atm. Properties The properties of air at 1 atm and the film temperature of ( T s + T ∞ )/2 = (98+25)/2 = 61.5 ° C are (Table A-15) Vapor 2 kg/h Water 100 ° C Pan T s = 98 ° C ε = 0.95 Air T ∞ = 25 ° C 1- 2 5 K 00299 . K ) 273 5 . 61 ( 1 1 7198 . Pr /s m 10 910 . 1 C W/m. 02819 . = + = = = × = ° = − f T k β υ Analysis ( a ) The characteristic length in this case is the height of the pan, m. 12 . = = L L c Then, 6 2 2 5 3-1 2 2 3 10 299 . 7 ) 7198 . ( ) /s m 10 910 . 1 ( ) m 12 . )( K 25 98 )( K 00299 . )( m/s 81 . 9 ( Pr ) ( × =...
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This note was uploaded on 01/24/2012 for the course PHY 4803 taught by Professor Dr.danielarenas during the Fall '10 term at UNF.

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