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

CBET-1236062PI：KANDLike在限制基板温度的同时，高热流密度去除在电子冷却应用中是至关重要的。目前的处理器冷却要求达到1 kW/cm2的热流密度，而器件表面温度需要足够低，以使IC芯片内的结温保持在85°C以下。微通道内流动沸腾已被认为是满足这一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较差的换热性能一直是实现预期冷却性能的主要障碍。该项目致力于开发一种稳定、高性能的流动沸腾系统，以满足当前电子冷却的需求。这将通过一种新颖的带有锥形歧管的开放式微通道设计来实现。开放式微通道设计为蒸汽提供了一条低阻力通道，同时液体与基材保持接触，从而提供了有效的冷却，从而实现了成核和/或对流沸腾。通过在衬底上分别添加偏置的条形翅片和纳米线，将进一步提高换热系数和临界热流密度(安全运行时的最大可能热流密度)。锥形歧管为消除流动沸腾不稳定性提供了一种有效的途径。这些概念已经在皮？S实验室的初步实验中得到了验证。该项目的重点将是了解这种构型下流动沸腾的基本机理，并显著改善有水的换热性能。此外，还将研究FC87和乙醇作为工质。FC87是一种可直接用于电子散热应用的介电流体。乙醇也是一种介电流体，与FC87相比具有更好的传热性能。尽管乙醇是易燃的，但其优越的性能可能会与设计安全冷却系统所需的预防措施进行权衡。这项工作将由研究生和本科生完成，他们将在进行微尺度运输过程的高级研究方面获得实践经验。该项目的主要成果将是开发一种新型的高热流密度去除系统，在微尺度上了解流动沸腾的基本传热机理，并培养本科生和研究生。此外，参与该项目的学生和PI将与地区中学生展开互动。他们将被介绍到新兴的科学领域，包括先进的传热学概念、纳米结构的开发和寻求克服科学障碍的研究努力。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，这些项目将旨在模仿计划研究的一些关键方面。该项目还将在RIT的WE(工程女性)志愿者组织的高中女学生参观期间向她们展示。

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.