Thermodynamics HW Solutions 686

Thermodynamics HW Solutions 686 - Chapter 8 Internal Forced...

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Chapter 8 Internal Forced Convection 8-65 A compressor is connected to the outside through a circular duct. The power used by compressor to overcome the pressure drop, the rate of heat transfer, and the temperature rise of air 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. Properties We take the bulk mean temperature for air to be 15 ° 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 higher temperature. The properties of air at this temperature and 1 atm pressure are (Table A-15) /s m 10 568 . 1 C W/m. 02476 . 0 kg/m 225 . 1 2 5 - 3 × = ° = = υ ρ k 7323 . 0 Pr C J/kg. 1007 = ° = p C The density and kinematic viscosity at 95 kPa are P == 95 kPa 101.325 kPa atm 0938 . /s m 10 1.673 = ) /s)/(0.938 m 10 568 . 1 ( kg/m 149 . 1 ) 938 . 0 )( kg/m 225 . 1 ( 2 5 - 2 5 - 3 3 × × = = = Analysis The mean velocity of air is m/s 594 . 8 /4 m) (0.2 /s m 27 . 0
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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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