Microscale Heat Transfer Enhancement through Fluid Structure Interaction in the Slip Flow Regime

ameela为气体对流电子冷却应用提出了一种新的传热增强技术。使用带有微尺度柔性针翅表面阵列的散热片，在其基频下响应非定常流，有望显著提高散热率。所提出的柔性销鳍的小尺寸将导致在鳍表面发生滑移流动。滑移流动和表面温度跳变的非连续效应，再加上流体结构相互作用（FSI），产生了一个独特而具有挑战性的计算问题，这是以前从未研究过的。现有的方法将结合计算流体动力学算法（ICE）和物质点法（MPM）进行固体建模，以考虑稀薄气体和可变形表面之间的动量和能量交换。所得的FSI算法将使用四个具有代表性的滑移流案例进行验证，这些案例可用于分析和/或数值数据。这项工作将自然导致其他滑移流FSI研究，例如与原子力显微镜探针、微型隔膜泵和阀门、微型飞行器机翼和控制襟翼相关的研究。在MPM-ICE方法中实施并验证滑移流和温度跳跃条件后，将进行系统的研究，以获得对微尺度柔性销鳍（单个，成对和阵列）的FSI行为和传热增强的物理理解。单个微尺度柔性钉片的研究将a)证实在连续介质中雷诺数为Re 47时存在非定常流动，b)产生滑移流态中流动和传热特性的数据，这些数据是Re、Knudsen数Kn、鳍展弦比和材料性能的函数。两个微尺度柔性销翅的热流体相互作用，对准主流动方向，将被检查，以确定最佳的间距。考虑到前面提到的参数，将研究一组微尺度柔性销鳍，以确定最大总传热率的最佳配置。智力优势：在滑移流态中流体结构相互作用的计算建模尚未在文献中报道。因此，拟议的项目预计将具有变革性，为许多新型微和纳米流体系统的设计和分析提供一种使能技术，包括拟议的用于增强空气侧传热的微尺度柔性pin鳍概念。来自连续流动刚性钉片和微尺度柔性钉片研究的数据将增加对复杂FSI系统中与阻力和传热增强有关的机制的理解。此外，还将首次为滑移流中同时存在动量和热输运的FSI系统提供数据。更广泛的影响：该算法将使在滑移流动状态下发生流体结构相互作用的系统建模成为可能。许多其他微尺度系统，如颗粒流、两相流和微致动器，都可以用改进的MPM-ICE方法进行建模。微尺度柔性引脚鳍阵列的优化设计可以广泛应用于各种电子封装，以增强空气冷却应用中的散热能力。通过将项目成果引入工程学院现有的两门本科/研究生课程，将对当地产生影响。项目结果将通过经审查的档案期刊出版物和在多学科会议上的发言向科学界传达，为思想的交流提供机会。参与该项目的研究生将从工程领域代表性不足的群体中积极招募。研究成果将转化为引人入胜的视频演示，用于外联和招聘活动。利用现有的工程学院活动，工程领域未被充分代表的群体将成为拓展的重点。这些项目的例子包括犹他州的“工程师：全州范围内的成长倡议”，这是一项由美国国家科学基金会资助的旨在提高工程毕业率的倡议，以及Hi-GEAR女孩夏令营，这是一个针对高中女生的住宿暑期项目。

0933574AmeelA novel heat transfer enhancement technology is proposed for gas convection electronic cooling applications. Use of heat sinks with surface arrays of microscale flexible pin fins, oscillating at their fundamental frequency in response to unsteady flow, is expected to significantly increase heat dissipation rates. The small size of the proposed flexible pin fins will result in slip flow occurring on the fin surface. Non-continuum effects of slip flow and temperature jump at the surface, coupled with fluid structure interaction (FSI), produces a unique and challenging computational problem that has not been investigated before. An existing methodology that combines a computational fluid dynamics algorithm (ICE) with the material point method (MPM) for solids modeling will be modified to account for the momentum and energy exchange between a rarified gas and a deformable surface. The resulting FSI algorithm will be validated using four representative cases of slip flow for which analytical and/or numerical data are available. The proposed work will naturally lead to other slip flow FSI studies, such as associated with atomic force microscope probes, microscale diaphragm pumps and valves, and micro air vehicle wings and control flaps. Following the implementation and validation of slip flow and temperature jump conditions into the MPM-ICE methodology, a systematic study will be conducted to gain physical understanding into the FSI behavior and heat transfer enhancement of microscale flexible pin fins, individually, in pairs, and in arrays. Single microscale flexible pin fin studies will a) confirm the existence of unsteady flow at Reynolds numbers Re 47 in the continuum regime and b) produce data for the flow and heat transfer characteristics in the slip flow regime as functions of Re, Knudsen number Kn, fin aspect ratio, and material properties. The thermal fluid interaction of two microscale flexible pin fins, aligned with the principal flow direction, will be examined to determine optimal spacing. An array of microscale flexible pin fins will be studied to ascertain optimal configurations for maximum overall heat transfer rates, taking into account the previously mentioned parameters. Intellectual Merit: Computational modeling of fluid structure interaction in the slip flow regime has not been reported in the literature. Thus, the proposed project is expected to be transformative, resulting in an enabling technology for the design and analysis of a number of novel micro- and nano-fluidic systems, including the proposed microscale flexible pin fin concept for enhancement of air-side heat transfer. Data from continuum flow rigid pin fins and microscale flexible pin fin studies will increase the understanding of mechanisms related to drag and heat transfer enhancement in this complex FSI system. In addition, for the first time, data will also be produced for a system with FSI in the slip flow regime with concurrent momentum and thermal transport.Broader Impacts: The algorithm will enable modeling of systems in which fluid structure interaction takes place in the slip flow regime. Many other microscale systems, such as particulate flows, two-phase flows, and microactuators could be modeled with the modified MPM-ICE methodology. The optimized design of microscale flexible pin fin arrays could be extensively applied to a wide variety of electronic packages to enhance heat dissipation in applications limited to air cooling. Local impact will occur through the introduction of project results into two existing undergraduate/graduate course within the College of Engineering. Project results will be conveyed to the scientific community through refereed archival journal publications and by presentations at multidisciplinary meetings, providing opportunities for cross-fertilization of ideas. Graduate students involved in the project will be actively recruited from underrepresented groups in engineering. Research outcomes will be converted into engaging video presentations for outreach and recruitment activities. Underrepresented groups in engineering will be the focus of outreach, utilizing existing College of Engineering activities. Examples of these programs include Utah's Engineers: A Statewide Initiative for Growth, an NSF-funded initiative to increase engineering graduation rates, and Hi-GEAR Girls Summer Camp which is a residence summer program for high school females.