Collaborative Research: Very High Heat-flux Cooling through Stable Energy-Efficient Macro-scale Partial Flow-boiling Using Microstructured Surfaces and Ultrasonics

各行各业对高功率密度电子器件的迫切需求创造了对高效和具有成本效益的冷却解决方案的迫切需求。一种有前途的方法是利用先进和稳定的流动沸腾过程，使用环境友好的介电流体，其沸点温度低（40-50℃）接近大气压，最大允许芯片温度与冷却介电流体之间的工作温差相对较小。该项目将展示一种高效的冷却策略，采用高热流密度（50 - 200 W/cm2或更高）的Novec/ 3m工程流体的高度稳定和节能的局部流动沸腾。所提出的方法将涉及充满流体的微结构表面，这些表面经历特殊的结构和亚结构微纳米级振动，消耗非常少的能量。这种方法的一个吸引人的好处是产生明显更高的压力蒸汽（比其他方法多2-3倍），能够从冷却热交换器中回收大量废热：允许这些现象，当扩展到大型系统（如数据中心）时，回收大部分废热（例如，仅从数据中心全球回收200太瓦时）作为清洁电力。提出的研究将利用具有充满流体的微结构沸腾表面的毫米级散热器的部分流动沸腾的稳定节能冷却性能来增强核沸腾（ENB）。该提案将通过利用子结构（即频率为1-10 MHz，振幅为nm/ μ m范围的网状金属丝）的压电诱导的超声波微振动引起的声热效应，在100至10,000 Hz的声频范围内叠加振幅调制，从而在非均核气泡中实现显著且可持续的汽化速率，从而产生μ m尺度的振幅。声波频率将促进有效和共振的结构微振动，交替增强液体再润湿和从微观结构沸腾区域去除微气泡，使它们过渡到散热器内的宏观两相流。因此，ENB将通过共振和节能的结构和子结构微振动的协同结合来实现。此外，这种方法引起的额外加热将在蒸汽中产生高压，可以用来开发新的废热回收技术。因此，该提案具有为高功率密度设备开发新型节能环保冷却解决方案的潜力，以及改进废热回收的策略，将在数据中心和混合动力汽车市场中得到重要应用。此外，该项目将促进大学与产业的合作，通过学生指导促进人力资源开发，并有助于促进该领域的多样性和包容性。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The urgent demand for high power-density electronic devices in various industries has created a pressing need for efficient and cost-effective cooling solutions. One promising approach is the utilization of advanced and stable flow-boiling processes, employing environmentally friendly dielectric fluids with low boiling temperatures (40-50 deg C) near atmospheric pressures, and relatively small operating temperature differences between the maximum allowable chip temperatures and the cooling dielectric fluid. This project will demonstrate an efficient cooling strategy by employing highly stable and energy-efficient partial flow-boiling of Novec/3M-engineered fluids at high heat fluxes (50 - 200 W/cm2 or more). The proposed approach will involve fluid-filled microstructured surfaces that undergo special structural and sub-structural micro-nano-scale vibrations, consuming very small amounts of energy. An attractive benefit of this approach is the generation of significantly higher pressure vapor (2-3 times more than other approaches), enabling significant waste heat recovery from cooling heat exchangers: allowing these phenomena, when scaled to large systems (such as data centers), to recover a large portion of the waste heat (e.g., 200 TWh globally from data centers alone) as clean electricity.The proposed research will leverage the stable energy-efficient cooling performance of partial flow-boiling in a millimeter-scale heat sink with a fluid-filled microstructured boiling surface for enhanced nucleate boiling (ENB). This proposal will deliver on achieving significant and sustainable vaporization rates within the heterogeneously nucleated bubbles by leveraging the acoustothermal effects caused by piezo-induced ultra-sonic micro-vibrations of the sub-structures (i.e. of mesh wires at frequency: 1-10 MHz; amplitude: nm/µm range), with superposed amplitude modulations at sonic frequencies ranging from 100 to 10,000 Hz and resulting in µm-scale amplitudes. The sonic frequencies will promote efficient and resonant structural micro-vibrations, alternately enhancing both liquid rewetting and the removal of micro-bubbles from the microstructured boiling region, allowing them to transition into the macro-scale two-phase flow within the heat sink. Hence, ENB will be achieved through the synergistic combination of resonant and energy-efficient structural and sub-structural micro-vibrations. Furthermore, the additional heating induced by this approach will generate high pressures within the vapor that can be harnessed to develop new waste heat recovery technologies. This proposal, therefore, with the potential to develop novel energy-efficient and environment-friendly cooling solutions for high-power density devices as well as strategies for improved waste heat recovery will have significant applications in data centers and the hybrid electric vehicle market. Furthermore, the project will foster university-industry collaborations, facilitate human resources development through student mentoring, and contribute to promoting diversity and inclusiveness within the field.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.