With increased focus on miniaturization and high performance in electronics, thermal management is a very important area of research today. In multiple applications such as portable electronics, consumer electronics, military applications, automobile, power electronics, high performance computing, etc. innovative thermal management strategies are necessary. In this work, two novel approaches to dissipate redundant heat better- first by novel carbonaceous-nanoparticle additives to develop thermal interface materials with superior performance and the second by using advanced metal additive manufacturing techniques to design and analyze metal-lattice based heat sinks are presented.
Thermal Interface Materials with multiple carbon-based nanoparticle fillers such as coal-derived Multi Layered Graphene (MLG), standard reduced Graphene Oxide (rGO), Multi-Walled Carbon Nano Tubes (MWCNTs), and Graphene Nano-Platelets (GNPs) in thermal paste were synthesized and seen to have superior heat dissipation properties. Also, graphene was synthesized from coal through an in-house, facile, scalable and cost-effective process. The enhancement in thermal conductance varies from ~70% in the coal-MLG to ~14% in MWCNTs-based TIMs. Noteworthy is ~3.5 times larger enhancement in thermal performance with the in-house coal-derived-MLG as compared to the commercially available g-MLG. At a 3% wt. fraction of coal-MLG, enhancement in thermal conductance was almost 120% higher compared to the base thermal grease.
In the second part, metal lattice-based heat sinks are designed for additive manufacturing for use in passive cooling of high-flux thermal management. A parametric optimization based on the lattice geometry, thickness, and height subject to additive manufacturing constraints is conducted. Intricate metal lattices with low mass based on the Simple Cubic, Octet, and Voronoi structures were generated by implicit modelling in nTopology® and their thermal performance was analyzed through numerical analysis using commercial CFD packages. The Voronoi lattice performed best with a significant improvement in thermal performance (~18% reduction in junction temperature difference with respect to ambient) as compared to a standard baseline Longitudinal heat Sink (LHS), while reducing the mass of the heat sink by ~2.1 times. Such optimized metal lattice-based heat sinks can lead to significant downsizing, reduction in overall mass and cost in applications where thermal management is critical with a need for low mass. We believe that such novel scalable materials and processes suited for mass production could be critical in meeting the material, design and product development needs to tackle the thermal management challenges of the future. / Master of Science / With increase in demand of high power and performance in electronics, there is a concurrent increase in redundant heat that needs to be dissipated. With enhanced focus and push towards electric vehicles, defense, consumer electronics, datacenter and supercomputing applications, electronics cooling is a critical area of research today. There are two primary resistances to heat- as it is removed from electronics package to the surrounding atmosphere – due to the thin layer of a material called Thermal Interface Material (TIM) at the interface between the heat sink and the package, and the resistance offered by the heat sink itself. In this work, a two-pronged approach for better cooling in electronics is presented. Firstly, carbon-based nano-sized particles are used to synthesize novel TIMs that provide superior heat transport capabilities as compared to a standard baseline. In the second approach, complex metal-lattice based heat sinks are designed for manufacturing with advanced techniques such as metal 3D printing.
Multiple carbon-based nano-particle additives such as Multi Layered Graphene synthesized from coal (MLG), standard commercially available reduced Graphene Oxide (rGO), Multi-Walled Carbon Nano Tubes (MWCNTs), and Graphene Nano-Platelets (GNPs) are dispersed in thermal paste and all of the resulting composites were found to remove heat better from electronics packages. The improvement in this ability varies from ~70% in the coal-MLG to ~14% in MWCNTs-based TIMs. Noteworthy is ~3.5 times larger enhancement in the heat transport ability with the use of in-house coal-derived-MLG as compared to the commercially available g-MLG. At an 3% wt. fraction of coal-MLG, there was a 1.2x increase in thermal performance as compared to the base thermal grease. Also, it is significant to mention that MLG was synthesized from coal through an in-house, facile scalable and cost-effective process. In the second part, metal lattice-based heat sinks designed for metal 3D printing for use in passive cooling of electronics was investigated. Multiple geometric parameters such as the lattice type, thickness, and height subject to additive manufacturing constraints were studied. Intricate metal lattices with low mass based on three structures- Simple Cubic, Octet, and Voronoi were generated by implicit modelling, and their thermal performance was predicted by computer based-simulations using commercial CFD packages. The Voronoi lattice performed best with a significant reduction (~18%) in junction temperature difference with the surrounding atmosphere- as compared to a standard baseline rectangular heat sink design, while simultaneously reducing the mass of the heat sink by ~2.1 times. Such optimized metal lattice-based heat sinks can lead to significant reduction in overall mass, size, and cost in weight sensitive applications. We believe that such novel scalable materials, designs, and processes suited for mass production could be critical in meeting the material, design and product development needs to tackle the thermal management challenges of the near future.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/110951 |
| Date | 27 June 2022 |
| Creators | Bharadwaj, Bharath Ramesh |
| Contributors | Mechanical Engineering, Mahajan, Roop L., Boreyko, Jonathan B., Huxtable, Scott T. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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