Enhanced Flow Boiling Heat Transfer at Microscale for Stable, High Heat Flux Removal

CBET-1236062 PI：Kandlikar在限制基板温度的同时，高热流量的去除在电子冷却应用中至关重要。目前的处理器冷却要求达到1 kW/cm 2的热通量，而器件表面温度需要足够低，以保持IC芯片内的结温低于85 °C。微通道内的流动沸腾被认为是满足这种冷却需求的一种潜在的冷却技术。然而，微通道内流动沸腾的不稳定性和传热性能差一直是实现理想冷却性能的主要障碍，本项目的努力是专门针对开发一个稳定的，高性能的流动沸腾系统，以满足当前电子冷却的需求。这将通过具有锥形歧管的新型开放微通道设计来实现。开放的微通道设计为蒸气提供低阻力路径，同时液体保持与基底接触，从而由于成核和/或对流沸腾而提供有效的冷却。通过在衬底上分别增加偏置的条形翅片和纳米线，可以进一步提高传热系数和临界热流密度（安全运行时的最大热流密度）。锥形歧管为消除流动沸腾不稳定性提供了一种有效途径。这些概念已在PI的初步实验中得到验证？s实验室。该项目的重点将是了解这种配置中流动沸腾的基本机理，并显着提高水的传热性能。此外，FC 87和乙醇也将作为工作流体进行研究。FC 87是一种可直接用于电子冷却应用的介电流体。乙醇也是一种介电流体，与FC 87相比具有更好的传热性能。虽然乙醇是易燃的，但其上级性能可能会与设计安全冷却系统所需的预防措施相权衡。这项工作将由研究生和本科生完成，他们将获得对微尺度传输过程进行高级研究的实践经验。该项目的主要成果将是开发一种新型的高热流去除系统，了解微尺度流动沸腾过程中的基本传热机制，并教育本科生和研究生。此外，学生和PI工作的项目将开放互动与地区中学生。他们将被介绍到新兴的科学领域，包括先进的传热概念，纳米结构的发展和研究工作，以寻求克服科学障碍。来自当地城市学校的学生计划每周访问RIT一次，与研究生互动，并从模拟项目中学习，这些项目将直接模仿计划研究的一些关键方面。该项目还将在RIT的WE（工程妇女）志愿者组织的访问期间向高中女生展示。

CBET-1236062PI: KandlikarHigh heat flux removal while limiting the substrate temperature is critical in electronics cooling application. Current processor cooling demands are seen to reach a heat flux of 1 kW/cm2 while the device surface temperature needs to be low enough to keep the junction temperatures below 85 °C within the IC chip. Flow boiling in microchannels has been identified as a potential cooling technique to meet this cooling demand. However, the boiling instability and poor heat transfer performance during flow boiling in microchannels have been major impediments in realizing the desired cooling performance.The project effort is directed specifically at developing a stable, high performance flow boiling system to meet the current electronics cooling demands. This will be accomplished by a novel open microchannel design with tapered manifolds. The open microchannel design provides a low resistance pathway for vapor while the liquid remains in contact with the substrate providing efficient cooling due nucleate and/or convective boiling. Further enhancements in heat transfer coefficient and critical heat flux (maximum possible heat flux under safe operation) will be achieved by adding offset strip-fins and nanowires respectively on the substrate. The tapered manifold provides an effective way to eliminate the flow boiling instability. These concepts have been validated in the preliminary experiments in the PI?s lab. The focus of the project will be to understand the basic mechanism of flow boiling in this configuration and significantly improve the heat transfer performance with water. In addition, FC87 and ethanol will also be investigated as working fluids. FC87 is a dielectric fluid that can be directly used in electronics cooling application. Ethanol is also a dielectric fluid and has a better heat transfer performance compared to FC87. Although ethanol is flammable, its superior performance may be weighed against the precautions needed in designing safe cooling systems. The work will be done by graduate and undergraduate students who will gain hand-on experience on conducting advanced research on microscale transport processes. The major outcomes of the project will be developing a novel high heat flux removal system, understanding the basic heat transfer mechanisms during flow boiling at microscale, and educating undergraduate and graduate students. In addition, the students and PI working on the project will open interactions with area middle school students. They will be introduced to the emerging scientific areas including advanced heat transfer concepts, nanostructure development and research endeavors in quest of overcoming scientific barriers. Student from a local city school are scheduled to visit RIT once every week to interact with graduate students and learn from simulated projects that will be directed towards mimicking some of the key aspects of the planned research. The project will also be showcased to female students from high schools during their visits organized by WE (Woman in Engineering) volunteers at RIT.