Chapter 7 External Forced Convection7-11CThe friction coefficient represents the resistance to fluid flow over a flat plate. It is proportional to the drag force acting on the plate. The drag coefficient for a flat surface is equivalent to the mean friction coefficient. 7-12CThe friction and the heat transfer coefficients change with position in laminar flow over a flat plate. 7-13CThe average friction and heat transfer coefficients in flow over a flat plate are determined by integrating the local friction and heat transfer coefficients over the entire plate, and then dividing them by the length of the plate. 7-14 Hot engine oil flows over a flat plate. The total drag force and the rate of heat transfer per unit width of the plate are to be determined. Assumptions1Steady operating conditions exist. 2The critical Reynolds number is Recr= 5×105. 3 Radiation effects are negligible. PropertiesThe properties of engine oil at the film temperature of (Ts+ T∞)/2 = (80+30)/2 =55°C = 328 K are (Table A-13) 1505PrCW/m.141.0/sm10123kg/m867263=°=×=υ=ρ−kAnalysisNoting that
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