Comparative Assessment of Flow Patterns and Hydrodynamics in Cylindrical and Hourglass-Shaped Pin-Fin Configurations

Electronic devices require efficient cooling to prevent overheating and ensure reliability. Pin-fins, commonly used in devices like computer processors and LED lighting, enhance heat transfer. Micro-pin-fin arrays in forced-flow heat exchangers are vital for intense cooling. Exploration of pin-fin shapes is needed to maximize heat transfer. Therefore, understanding flow patterns and coherent structures in pin-fin arrays is crucial. They offer insights into heat transfer mechanisms and ways to enhance thermal performance. Our research aims to compare flow patterns between cylindrical and hourglass-shaped pin-fins via URANS simulations using OpenFOAM CFD software. We conducted a numerical analysis of hydraulic resistance and flow patterns in both cylindrical and hourglass-shaped pin-fin arrays, utilizing Ω criteria and critical point theory. Our key findings indicate that using hourglass-shaped pin-fins in microchannel heat exchangers can reduce hydraulic resistance by 6% to 12%. Additionally, vortical structures exhibit similar patterns near the endwall region, where flow detachment leads to the formation of a horseshoe vortex. Furthermore, behind hourglass-shaped pins, colliding streams change direction more abruptly, resulting in heightened mixing, the creation of intricate vertical patterns, and an increased prevalence of smaller structures when compared to cylindrical pin-fins.