Heat Transfer Enhancement Simulation Employing Flat and Curved Winglet Vortex Generator Pairs with Punched Holes

To comprehend heat transfer mechanisms, the study examines the flow and thermal characteristics of flat and curved vortex generators with punched holes on their surfaces.Re is varied from 3,000 to 18,000 in three-dimensional numerical simulations in a channel flow with two VGs mounted on the bottom wall.The improvement of heat transfer and pressure loss are investigated using the dimensionless parameters Num/Num0, f/f0, and R =(Num/Num0)/(f/f0).The results indicate that VGs with punched holes have higher Num/Num0 values compared to VGs without punched holes across all Re values.The most significant difference, up to 6.4%, is observed between VGs with openings (DWH) and VGs without punched holes (DWP) at Re=12,000.The apparent friction factor (f/f0), initially increases rapidly and then stabilizes with Re.The DWP has the highest friction factor f/f0, ranging from 1.1 to 1.7, due to the larger area that confronts the airflow in the P-series of VGs, followed by DWH.Curved VGs CDW and CDWH are more effective in reducing drag and lowering f/f0 compared to plane VGs due to their streamlined shape.The jet flow from the perforations helps clear stagnant fluids and reduce pressure differences before and after the VGs.Also, the hydraulic heat capacity R is more effective in a curved VG than in a flat VG because of the improved heat transfer and lower wire flow.The thermo-hydraulic efficiency coefficient is determined by Colburn and friction coefficients, and CDWH has the highest resistance, followed by CDWP, DWH, and DWP.When Re=18,000, a rectangular VG with holes performs better than one without, with a maximum difference of 35.3%.