Capillary and Boiling Limits of Micropillared Thermal Wicks

PI：Carlos HidrovoProposal#：1134104这个项目旨在了解相变微结构中毛细极限流动背后的主导物理，目的是开发能够散热到1kW/cm2以上的热芯。该项目的变革性方面在于为微观结构几何对热相变毛细管流动系统的影响提供了新的见解。此外，这一认识将导致基于垂直微柱阵列的新型芯吸结构的开发，用于热管和蒸汽室应用，能够获得前所未有的低温热流。具体地说，该项目将解决和阐明垂直刻蚀硅微柱阵列中毛细管流背后的主导物理，特别是与相变热传输应用相关的物理问题。该项目将解决以下问题：(1)微结构如何影响毛细管流？(2)在这种毛细管抽吸结构中，控制毛细管抽吸能力的关键参数是什么？(3)热传递和相变过程如何与毛细管流相耦合？(4)微柱毛细管形式的MEMS技术能否作为一种超过当前热管和蒸汽室热流散热能力的手段来实施？为了回答这些问题，已经确定了以下具体任务：(I)引入一种新的实验装置，能够同时获得不同芯材样品的热和毛细管流动数据。该系统将用于评估硅基微柱样品的热工水力性能。(Ii)制造硅基微柱撑芯，具有精确控制的不同几何结构的微结构。(3)实验结果将得到紧凑模型的补充和验证，这些模型将捕捉与这些系统中的毛细流动、相变(沸腾)和热传输相关的物理现象。(4)实验和建模的耦合结果将被用作优化硅微柱阵列样品的理想微结构几何结构的设计工具。该项目的智力价值包括阐明微几何结构对相变毛细管系统的影响。由于开发的模型和进行的实验都将在具有已知几何形状的特殊设计的样本上进行，因此潜在的物理学将有一个更清晰的背景。这将有助于更好地了解影响相变热力系统中毛细管流动的关键参数。从这项研究中学到的经验教训将延续到对非规则和非均匀结构上的相变毛细流动的理解，如分形体。该项目的更广泛影响包括在多孔介质中毛细流动的一般领域具有重要的相关性，对地质学、水文学和制造等领域具有重大影响。这里要解决的问题提出了丰富的工程、物理和材料挑战，对研究生和本科生来说是很棒的跨学科项目。PI是实验热流体、MEMS和光学诊断领域的年轻领导者。该项目的成果将为PI教授或目前正在开发的课程提供新的课堂材料，以及针对小学受众的外联活动。重要的是，PI将启动本科暑期实习计划，目标是代表不足的德克萨斯大学一年级和二年级学生，真正培养他们成为未来工程挑战的多学科领导者。

PI: Carlos HidrovoProposal #: 1134104This project aims to understand the governing physics behind capillary limit flow in microstructures with phase change, with the objective of developing thermal wicks capable of dissipating upwards of 1 kW/cm2. The transformative aspect of the project resides in providing new insights into the effects that microstructure geometry has on thermal-phase change capillary flow systems. Furthermore, this understanding will lead to the development of novel wicking structures based on vertical micropillared arrays for heat pipe and vapor chamber applications capable of low temperature heat fluxes not seen before.Specifically, the project will tackle and elucidate the governing physics behind the capillary flow within arrays of vertically etched silicon micropillars, particularly related to phase change heat transfer applications. The following questions will be addressed by the project: (1) How does microstructure affect capillary flow? (2) What are the key parameters that control capillary pumping capabilities in such wicking structures? (3) How are heat transfer and phase change processes coupled to the capillary flow? (4) Can MEMS technology, in the form of micropillared wicks, be implemented as a means of exceeding current heat pipe and vapor chamber heat flux dissipation capabilities? In order to answer these questions, the following specific tasks have been identified: (i) Introduction of a novel experimental setup capable of simultaneously obtaining thermal and capillary flow data for different wick samples. This system will be used to assess the thermo-hydraulic performance of silicon based micropillar samples. (ii) Fabrication of silicon based micropillared wicks, with precisely controlled microstructure of varying geometry. (iii) The experimental results will be complemented by and validated against compact models that will capture the relevant physics associated with the capillary flow, phase change (boiling), and thermal transport in these systems. (iv) The coupled experimental and modeling results will be used as a design tool towards optimization of ideal microstructure geometries for the silicon micropillar array samples.The intellectual merit of the project includes elucidating the impact that micro-geometry have on phase change capillary systems. Since both the models developed and the experiments conducted will be done on specially designed samples with known geometry, the underlying physics will have a much clearer context. This will allow for better understanding of the key parameters that affect capillary flow in thermal systems with phase change. Lessons learned from this research will carry over to the understanding of capillary flow with phase change on non-regular and non-uniform structures, such as fractals.The broader impact of the project includes having significant relevance in the general area of capillary flow in porous media, with major implications for fields such as geology, hydrology and manufacturing. The problems to be tackled here present rich engineering, physics, and materials challenges, great cross-disciplinary projects for the graduate and undergraduate students involved. The PI is a young leader in experimental thermal fluids, MEMS and optical diagnostics. The results of the project will provide new classroom materials for courses that the PI teach or is currently developing, as well as outreach activities geared towards elementary school audiences. Importantly, the PI will initiate an undergraduate summer internship program, aimed at underrepresented UT freshmen and sophomores to truly prepare them as multidisciplinary leaders of future engineering challenges.