Laminar forced convection heat transfer to ordered and disordered single rows of cylinders

We study laminar forced convection heat transfer to or from a single row of equidistantly and non-equidistantly spaced parallel cylindrical wires, perpendicular to the flow direction. We report average Nusselt numbers as a function of geometry and flow conditions, for open frontal area fractions between 0.04 and 0.95, Prandtl numbers between 0.7 and 10, and Reynolds numbers (based on the wire diameter and the free stream velocity) between 0.001 and 600. For equidistantly spaced rows of cylindrical wires we propose a general analytical expression for the average Nusselt number as a function of the Reynolds number, Prandtl number and the open frontal area fraction, as well as asymptotic scaling rules for small and large Reynolds. For all studied Prandtl numbers, equidistant rows exhibit decreasing average Nusselt numbers for decreasing open frontal area fractions at low Reynolds numbers. For high Reynolds numbers, the Nusselt number approaches that of a single cylinder in cross-flow, independent of the open frontal area fraction. For equal open frontal area fractions, the Nusselt number in non-equidistant rows is lower than in equidistant rows for intermediate Reynolds numbers. For very low and high Reynolds numbers, non-uniformity does not influence heat transfer.