Adaptive Hotspot Cooling with Self-Propelled Jumping Condensate

移动热点在电子系统中非常普遍，包括微处理器和电力电子系统，这些系统的计算任务和外部有效载荷都在不断变化。现有的冷却解决方案通常是为固定热点（如热电冷却器）或缓慢变化的热负荷（如平板热管）而设计的，因此不足以解决移动热点的冷却挑战。本研究旨在开发一种新的相变冷却机制，用于热点的自适应热管理，该机制利用超疏水表面液滴冷凝水的自推进跳跃来促进液体返回蒸发器。冷却系统由两个紧密间隔的平行板，一个超亲水性蒸发器和一个超疏水性冷凝器封闭的水/蒸汽组成。蒸发器上的热点驱动工作流体蒸发，然后在对面的板上凝结。当多个凝析液滴结合在一起时，释放的表面能推动合并后的液滴垂直跳回热点，完成液体回流，维持相变过程。自适应冷却是通过工作流体在热点处的优先蒸发和在极短的板间距离上的快速跳跃返回来实现的。跳凝方法提供了一个独特的热点冷却能力组合：(i)对移动热点的快速响应；（ii）最小热梯度的自适应冷却；（三）不受外力影响的被动冷却。在简单标度定律指导下，通过综合实验和数值研究，对自适应热点冷却条件下的自航跳跃凝结水进行了研究。在界面传输现象方面，该项目有望对表面能量驱动的跳跃过程产生物理见解，这种过程在自然界中被广泛观察到，可能对改进工业冷凝器有用。在热传输过程方面，该项目为相变系统中的冷凝水返回提供了一种全新的机制，并为移动热点的自适应热管理提供了一种新方法。该项目在实现移动热点的热管理方面具有潜在的变革性，而移动热点是最先进的微处理器和电力电子性能的瓶颈。提出的研究也适用于促进自我持续滴状冷凝，特别是在有利的外力可能不存在的应用（例如航天器冷却），以及开发仿生材料和收集界面能的系统（例如防露材料）。除了培养研究生和吸引少数族裔本科生参与STEM研究外，该项目还将努力向K-12学生和公众推广。通过PI？一名高中教师将继续翻译PI的前沿研究。在teachengienering.org上发布的美国实验室的参考课程单元。在适当的时候，该项目还将利用PI？他曾与探索频道（Discovery Channel）等主要媒体成功合作，传播研究成果。

CBET-1236373Chuan-Hua ChenDuke UniversityMobile hotspots are prevalent in electronic systems, including microprocessors and power electronics with constantly changing computing tasks and external payloads. Existing cooling solutions are generally designed for fixed hotspots (e.g. thermoelectric coolers) or slowly varying heat loads (e.g. flat plate heat pipes), and are therefore not adequate to address the cooling challenges of moving hotspots. This study aims at developing a novel phase-change cooling mechanism for adaptive thermal management of hotspots, where the self-propelled jumping of dropwise condensate on superhydrophobic surfaces is utilized to promote liquid return to the evaporator. The cooling system consists of water/vapor enclosed by two closely spaced parallel plates, a superhydrophilic evaporator and a superhydrophobic condenser. The hotspots on the evaporator drive the working fluid to vaporize and then condense on the opposing plate. When multiple condensate drops coalesce together, the released surface energy propels the merged drop to jump perpendicularly back to the hotspots, completing the liquid return and sustaining the phase change process. The adaptive cooling is accomplished by the preferential evaporation of the working fluid at the hotspots and the rapid jumping return across the very short inter-plate distance. The jumping-condensate approach offers a unique combination of hotspot cooling capabilities: (i) rapid response to moving hotspots; (ii) adaptive cooling for minimal thermal gradients; and (iii) passive cooling independent of external forces. Through integrated experimental and numerical investigations that are guided by simple scaling laws, the self-propelled jumping condensate will be studied in the context of adaptive hotspot cooling. In terms of interfacial transport phenomena, the project is expected to yield physical insights to surface-energy-powered jumping processes, which are widely observed in nature and potentially useful for improving industrial condensers. In terms of thermal transport processes, the project offers a fundamentally new mechanism for condensate return in phase change systems and a novel approach for adaptive thermal management of moving hotspots. This project is potentially transformative in enabling the thermal management of mobile hotspots which bottleneck the performance of state-of-the-art microprocessors and power electronics. The proposed research is also applicable to the promotion of self-sustained dropwise condensation, particularly for applications where favorable external forces may not exist (e.g. spacecraft cooling), and the development of biomimetic materials and systems harvesting interfacial energy (e.g. anti-dew materials). In addition to training graduate students and attracting minority undergraduates to STEM research, the project will strive to outreach to K-12 students and the general public. Through the PI?s ongoing CAREER program, a high school teacher will continue to translate cutting-edge research in the PI?s lab into refereed curricular units published at teachengienering.org. When appropriate, this project will also leverage the PI?s past successes with major media outlets such as the Discovery Channel to disseminate the research findings.