Influence of passive wake control on thermal-hydraulic performance of a cylinder confined in wavy channel under high blockage ratios.

Heat exchange devices involving confined heated cylinders in crossflow require wake stability to minimize hydraulic losses, which are typically accompanied by a considerable loss in heat transfer. To address this problem, passive wake control for laminar flow past a cylinder is introduced in the form of wavy channel walls around the cylinder. The resultant effects on heat transfer and drag are investigated in detail for a range of Reynolds numbers (Re = = 20–200), blockage ratios (β = 0.5–0.9) and Prandtl numbers (Pr = 0.25–100). For the given range of parameters, it is shown that the wavy channel reduces cylinder drag by a minimum of ∼ 36 % and a maximum of ∼ 95 %, at the expense of ∼ 8 % and ∼ 40 % loss in heat transfer, respectively, compared to the plane channel. Thermal-hydraulic performance of the wavy channel compared to the plane channel for Pr = 0.744, is improved by ∼ 14 % for β = 0.5 and ∼ 160 % for β = 0.9. Therefore, the performance enhancement brought about by the wavy channel provides an appropriate trade-off between drag reduction and heat transfer loss. [ABSTRACT FROM AUTHOR]