Chapter 7 External Forced Convection Flow Across Tube Banks 7-62C In tube banks, the flow characteristics are dominated by the maximum velocity V max that occurs within the tube bank rather than the approach velocity V . Therefore, the Reynolds number is defined on the basis of maximum velocity. 7-63C The level of turbulence, and thus the heat transfer coefficient, increases with row number because of the combined effects of upstream rows in turbulence caused and the wakes formed. But there is no significant change in turbulence level after the first few rows, and thus the heat transfer coefficient remains constant. There is no change in transverse direction. 7-64 Combustion air is preheated by hot water in a tube bank. The rate of heat transfer to air and the pressure drop of air are to be determined. Assumptions 1 Steady operating conditions exist. 2 The surface temperature of the tubes is equal to the temperature of hot water. Properties
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