Numerical analysis of convection heat transfer from an array of perforated fins using the Reynolds averaged Navier-Stokes equations and large-eddy simulation method

Extended surfaces (fins) are frequently used in heat exchange devices to increase the heat transfer between a primary surface and the surrounding fluid. In the present study, we determined the thermal performance of an efficient type of perforated fin and we compared the results with those obtained for a simple solid fin and a flat surface without fins in the same working conditions. The modeled geometry comprised fins that had small channels with a circular cross section and different configurations, which were arranged stream-wise along the fin's length. The turbulent flow field around the perforated fins was modeled using the Reynolds averaged Navier-Stokes (RANS) equations and large-eddy simulation (LES) method with a suitable subgrid-scale model. The conjugate differential equations for both the solid and gas phases were solved simultaneously using the finite volume procedure with the SIMPLE algorithm. For LES, the flow and heat transfer characteristics were determined for a Reynolds number equal to 3.2×104 based on the fin length and a Prandtl number of 0.71. The results indicated that among the different configurations, the fins with three openings had the best thermo-hydraulic performance. In addition, we found that although the heat transfer rates predicted by RANS and LES were in close agreement, there were noticeable differences in the important flow characteristics, such as the recirculation zone around the fins and the total drag force on them.