Influence of pin-perforation shape on thermohydraulic performance of circular pin-fin heat sinks under turbulent flow

Abstract

The impact of pin-perforation shape on the thermohydraulic performance of circular pin–fin heat sinks (CPFHS) under turbulent flow conditions is numerically assessed using a computational fluid dynamics software. The convective heat transfer efficiency, hydraulic resistance, and thermohydraulic performance of four pin-perforation shapes: square diamond, triangle, hexagon, and circle, are evaluated under various turbulent flow conditions (Reynolds number between 24,484 to 55,088). The sizes of all pin-perforation shapes are under a constraint that the ratio of the air–solid interfacial surface area to the total volume of pin-perforated CPFHS must be the same. The results show that all pin-perforated CPFHS demonstrate a higher Nusselt number compared to unperforated CPFHS. Those with circular perforations exhibit the highest Nusselt number with up to 39% improvement compared to unperforated CPFHS, followed by those with hexagonal, triangular, and diamond perforations, respectively. The Nusselt numbers correlate with the ease of fluid flow within perforations which is expressed using the average air velocities through perforations. In terms of hydraulic resistance, all pin-perforated CPFHS exhibit a reduction in friction factor compared to unperforated CPFHS. Among these, the largest decrease in friction factor, up to 15.8%, is observed in CPFHS featuring circular perforations, followed by those with hexagonal, diamond, and triangular perforations, respectively. The friction factors are influenced by the ratio of perforation perimeter to cross-sectional area. All pin-perforated CPFHS have a thermal performance factor greater than 1, indicating an improvement in thermohydraulic performance compared to unperforated CPFHS. CPFHS with circular perforations yield the highest thermal performance factor, reaching up to 1.44, followed by hexagonal, triangular, and diamond pin configurations, in descending order. With increasing Reynolds numbers, thermal performance factors of pin-perforated CPFHS initially rise, then gradually decline, suggesting that thermohydraulic advantages due to pin–fin perforations are diminishing as the flow become more turbulent.