Prediction Methodology for Hollow Hybrid Fins and Arrays under Natural Convection

Abstract

Recently, the need for electronic and photonic devices is increasing rapidly with higher demands such as smaller sizes with high efficiency and reliability while the cost is expected at low prices. Several electronic and photonic systems such as light-emitting diodes (LEDs), outdoor wireless devices, and defense electronics are located in various conditions including remote areas far from power sources and thus need highly energy efficiency. Heat sinks have been commonly used as passive cooling devices considering their robust design and promising price. However, research on optimum heat sink performance is continuously required to achieve effective thermal management in accordance with the growth of the electronic and photonic technology. In this study, Nusselt number correlations were developed to predict thermal behaviors of hollow hybrid fins (HHFs) and fin arrays under natural convection. The HHF is a hollow pin fin integrated with radially-placed plate fins and having a perforation near the fin base. The HHF array is a staggered array of the HHFs. The numerical models of the HHF and the HHF array were generated and validated by the measurement, and then wide-ranging thermal data were obtained using the CFD models. Nusselt number correlations for the HHF and the HHF array were generated utilizing the thermal data, obtained by the CFD models, by considering Rayleigh numbers and the primary geometric parameters such as external diameter, internal diameter, fin spacing, and the height of the HHF. The results show that the prediction of the correlations agrees well with the CFD calculation with reasonable discrepancy. The average discrepancy values of HHF correlations were 3.0% for low Ra (Ra<40000) and 2.7% for high Ra (Ra>40000). The average discrepancy values of HHF array correlations were 3.5% for Ra <9000, 8% for 9000