Chapter 8 Internal Forced Convection8-56The components of an electronic system located in a circular horizontal duct are cooled by forced air. The exit temperature of the air and the highest component surface temperature are to be determined. Assumptions1Steady flow conditions exist. 2The inner surfaces of the duct are smooth. 3The thermal resistance of the duct is negligible. 4Air is an ideal gas with constant properties. 5 The pressure of air is 1 atm. PropertiesWe assume the bulk mean temperature for air to be 310 K 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 A-15) ρυ==°=×=11430026816710060710...Pr.kg / mW/m. C10 m / sJ/kg. C3-52kCpAnalysis(a) The mass flow rate of air and the exit temperature are determined from Air 32°C 0.65 m3/min TeElectronics, 90 W L= 1 mD = 15 cm &&(.mV==ρ1143 kg / m )(0.65 m / min) = 0.74295 kg / min = 0.0124 kg / s
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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.