Thermodynamics HW Solutions 694

Thermodynamics HW Solutions 694 - Chapter 8 Internal Forced...

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Chapter 8 Internal Forced Convection 8-72 Integrated circuits are cooled by air flowing through a series of microscopic channels. The temperature rise of air across the microchannels and the average surface temperature of the microchannels are to be determined. Assumptions 1 Steady flow conditions exist. 2 The inner surfaces of the microchannels are smooth. 3 Entrance effects are disregarded. 4 Any heat transfer from the side and cover surfaces are neglected. 5 Air is an ideal gas with constant properties. 6 The pressure of air is 1 atm. Properties We assume the bulk mean temperature for air to be 60 ° C since the mean temperature of air at the inlet will rise somewhat as a result of heat gain through the microscopic channels whose base areas are exposed to uniform heat flux. The properties of air at 1 atm and 60 ° C are (Table A-15) 0.7202 Pr C J/kg. 1007 /s m 10 895 . 1 C W/m. 02808 . 0 kg/m
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