Chapter 8 Internal Forced Convection8-68EThe exhaust gases of an automotive engine enter a steel exhaust pipe. The velocity of exhaust gases at the inlet and the temperature of exhaust gases at the exit are to be determined. Assumptions1Steady flow conditions exist. 2The inner surfaces of the pipe are smooth. 3The thermal resistance of the pipe is negligible. 4Exhaust gases have the properties of air, which is an ideal gas with constant properties. PropertiesWe take the bulk mean temperature for exhaust gases to be 700°C since the mean temperature of gases at the inlet will drop somewhat as a result of heat loss through the exhaust pipe whose surface is at a lower temperature. The properties of air at this temperature and 1 atm pressure are (Table A-15) /sft105902.0FBtu/h.ft.0280.0lbm/ft03422.023-3×=°==υρk694.0PrFBtu/lbm.2535.0=°=pCNoting that 1 atm = 14.7 psia, the pressure in atm is P= (15.5 psia)/(14.7 psia) = 1.054 atm. Then, /sft100.5598=)/s)/(1.054ft105902.0(lbm/ft03608.0)054.1)(lbm/ft03422.0(23-23-33××===Exhaust 800°F 0.2 lbm/s80°
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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.