Numerical investigation of the thermo-hydraulic performance of a shark denticle-inspired plate fin heat exchanger

Abstract

Growing demand for increased power dissipation is fuelling the need for the design of more efficient heat exchangers. Modifying fin geometry is an effective way of improving heat transfer efficiency and of reducing flow resistance for plate fin heat exchangers. To date, fin designs have mostly revolved around classical shapes such as pins, ellipses, and rectangles, due to limitations of conventional manufacturing technologies. However, with recent advancements in metal additive manufacturing, there is an opportunity of redesigning approaches and ways of thinking to create novel fin geometries. In this study, biomimicry was used as a tool to reverse engineer a novel geometry for a plate fin heat exchanger based on a denticle, which is a mesoscopic structure on the skin of sharks. The shape of the denticle is streamlined; therefore, showing the possibility of enhancing fluid-to-solid contact if used as geometry for a plate fin heat exchanger. The thermo-hydraulic performance of the denticle was evaluated with respect to a rectangular, cylindrical and an elliptical fin (NACA 0030), using conjugate-heat-transfer simulations on ANSYS-Fluent. The numerical model was calibrated and validated based on experimental results from an additively manufactured rectangular plate fin heat exchanger. Results demonstrated that over the range of tested Reynolds Numbers, 9.8x104 < Re ≤ 22.9x104, the denticle fin had average Nusselt number improvements of 13.1 %, 5.4 % and 75.7 % with respect to the rectangular fin, the NACA 0030 and cylindrical fin, respectively. At Re = 22.9x104, a 26 % decrease in pressure drop was noted for the denticle with respect to the rectangular fin, with maximum thermal performance factors (ƞ) of 1.29, 0.81 and 1.53 as noted for the denticle fin with respect to the rectangular fin, NACA 0030 fin and cylindrical fin, respectively.