Natural Convection Cooled Hybrid Fin Heat Sinks

Abstract

Utilization of LED lighting modules have been rising in various settings like streetlights, retails, automobiles, home improvements, and other professional situations due to the advantages of LED such as longer lifespan, and higher energy efficiency. These two properties make LED lighting to be regarded as environmentally friendlier than their conventional lighting counterpart, especially when energy and climate change are a big issue in recent years. LED lighting provides cool lighting, unlike incandescent and fluorescent lamps that generate hot lighting. Still, the semiconductor generates the waste heat that needs to be dissipated to preserve the illumination performance and lifetime of a LED modules. In order to manage the waste heat, a sophisticated cooling system is developed. The research work summarized in this thesis presents a combined analytical, numerical, and experimental methods to investigate the thermal performance of hybrid fin heat sinks (HFHSs) under natural convection. Two proposed HFHSs structure are a solid hybrid fin heat sink (SHFHS), and a hollow hybrid fin heat sink (HHFHS). A pin fin heat sink (PFHS) is used as a comparison. To do this task, the followings were done. First, a numerical study was conducted using ANSYS software packages. CFD analysis was carried out to study a fin spacing, an internal channel, a heat dissipation, and the orientation effects on the HFHSs thermal performance. The fin spacing effects were examined to find the optimum spacing for the HFHSs. The internal channel diameters of a HFHS were varied from 0-5mm to analyze its impact to the HFHS thermal performance. Second, an experimental test rig was designed and manufactured to determine the heat dissipation, and the orientation effects on the SHFHS. The heat sinks were subjected to several heat dissipations and various angles from 0-180o with 22.5o increment, where 0o means heat sink base facing upward and 180o is downward facing heat sink base. The heat dissipations that were used for this measurement varies from 5 to 30W. Third, an analytical model was derived to predict the solid hybrid fin base temperature and compares it with the numerical result. The thermal performances are defined as the thermal resistance and the mass multiplied thermal resistance. 15 mm fin spacing was selected as a reference based on the fin spacing analysis. The SHFHS shows the best thermal performance, while the HHFHS thrives at the mass based thermal performance. These results were explained in the internal channel diameters study. The HFHSs outperform the PFHS with the observed maximum performance at 0-45o. The performance of all the tested heat sinks deteriorated after 45o. The better performances of the HFHSs are due to the enlarged surface area, the mass reduction, and the heat flow from the internal channel. These appealing results show the future of the HFHSs as a better alternatives to the PFHS for passive cooling applications.