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Unformatted text preview: Chapter 8 Internal Forced Convection 855 The components of an electronic system located in a rectangular horizontal duct are cooled by forced air. The exit temperature of the air and the highest component surface temperature are to be determined. Assumptions 1 Steady flow conditions exist. 2 The inner surfaces of the duct are smooth. 3 The thermal resistance of the duct is negligible. 4 Air is an ideal gas with constant properties. 5 The pressure of air is 1 atm. Properties We assume the bulk mean temperature for air to be 35 C since the mean temperature of air at the inlet will rise somewhat as a result of heat gain through the duct whose surface is exposed to a constant heat flux. The properties of air at 1 atm and this temperature are (Table A15) 7268 . Pr C J/kg. 1007 /s m 10 654 . 1 C W/m. 02625 . kg/m 146 . 1 2 5 3 = = = = = p C k Air 32 C 0.65 m 3 /min L = 1 m Air duct 16 cm 16 cm 90 W Analysis ( a ) The mass flow rate of air and the exit temperature are determined from...
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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.
 Fall '10
 Dr.DanielArenas
 Thermodynamics, Convection, Force, Mass

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