Thermodynamics HW Solutions 579

Thermodynamics HW Solutions 579 - Chapter 7 External Forced...

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Chapter 7 External Forced Convection 7-50E A fan is blowing air over the entire body of a person. The average temperature of the outer surface of the person is to be determined for two cases. Assumptions 1 Steady operating conditions exist. 2 Radiation effects are negligible. 3 Air is an ideal gas with constant properties. 4 The average human body can be treated as a 1-ft-diamter cylinder with an exposed surface area of 18 ft 2 . 5 The local atmospheric pressure is 1 atm. Properties We assume the film temperature to be 100 . The properties of air at this temperature are (Table A-15E) ° F 7260 . 0 Pr /s ft 10 1809 . 0 F Btu/h.ft. 01529 . 0 2 3 - = × = ° = υ k Analysis The Reynolds number is 4 2 3 10 317 . 3 /s ft 10 1809 . 0 ft) ft/s)(1 (6 Re × = × = υ = D V The proper relation for Nusselt number corresponding this Reynolds number is V = 6 ft/s T = 85 ° F Person, T s 300 Btu/h D = 1 ft [] [] 84 . 107 000 , 282 10 317 . 3 1 ) 7260 . 0 / 4 . 0 ( 1 ) 7260 . 0 ( ) 10 317 . 3 ( 62
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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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