Chapter 7 External Forced Convection7-46The wind is blowing across the wire of a transmission line. The surface temperature of the wire is to be determined. Assumptions1Steady operating conditions exist. 2Radiation effects are negligible. 3Air is an ideal gas with constant properties. 4 The local atmospheric pressure is 1 atm. PropertiesWe assume the film temperature to be 10°C. The properties of air at this temperature are (Table A-15) 7336.0Pr/sm10426.1CW/m.02439.0kg/m246.125-3=×=°==υρkAnalysisThe Reynolds number is [ ]4674/sm10426.1m)(0.006m/s0/3600)100(40Re25=××==−∞DVThe Nusselt number corresponding this Reynolds number is determined to be ()0.36000,282467417336.0/4.01)7336.0()4674(62.03.0000,282Re1Pr/4.01PrRe62.03.05/48/54/13/23/15.05/48/54/13/23/15.0=⎥⎥⎦⎤⎢⎢⎣⎡⎟⎟⎠⎞⎜⎜⎝⎛+++=⎥⎥⎦⎤⎢⎢⎣⎡⎟⎟⎠⎞⎜⎜⎝⎛+++
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