Sensitivity of Heat Transfer to the Cross Section Geometry of Cylinders

This study investigates the phenomenon of vortex shedding and the heat transfer performance of bluff bodies, including smooth and sharp-edged cylinders. The examined geometries include square, triangular, hexagonal, and bullet-shaped bodies. The results are compared with a smooth circular cylinder standardizing the hydraulic diameter (D_h) across all bluff bodies and maintaining a Reynolds number within the range of 100 ⩽ Re ⩽ 200. The thermofluidic results are carefully examined and compared to determine the optimal conditions for maximum heat transfer rates, as measured by the Nusselt number. It is found that the Strouhal number, and thus the vortex shedding frequency, of cylinders with smooth surfaces differs significantly from those with sharp edges. It is demonstrated that hexagonal cylinders have up to 33% higher St than other geometries. Due to the flow dynamics in the wake of the cylinders, the heat transfer rates are lowest in square geometry and highest in circular geometry. Based on the analysis, bluff bodies can be classified into two primary groups: (i) bluff bodies with up to four edges are classified as “nonsmooth bluff bodies,” and (ii) those with six or more edges behave similarly to “smooth surface cylinders.”