Chapter 7 External Forced Convection7-48 An aircraft is cruising at 900 km/h. A heating system keeps the wings above freezing temperatures. The average convection heat transfer coefficient on the wing surface and the average rate of heat transfer per unit surface area are to be determined. Assumptions1Steady operating conditions exist. 2Radiation effects are negligible. 3Air is an ideal gas with constant properties. 4The wing is approximated as a cylinder of elliptical cross section whose minor axis is 30 cm. PropertiesThe properties of air at 1 atm and the film temperature of (Ts+ T∞)/2 = (0-55.4)/2 = -27.7°C are (Table A-15) 7422.0Pr/sm10106.1CW/m.02152.025-=×=°=υk18.8 kPa V∞= 900 km/h T∞= -55.4°C Note that the atmospheric pressure will only affect the kinematic viscosity. The atmospheric pressure in atm unit is P==(..18801855kPa)1 atm101.325 kPaatm The kinematic viscosity at this atmospheric pressure is /sm10961.51855
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