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

在限制衬底温度的同时去除高热流密度在电子冷却应用中至关重要。目前的处理器冷却需求可以达到1 kW/cm2的热流密度，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已被确定为一种潜在的冷却技术来满足这种冷却需求。然而，微通道流动沸腾过程中的沸腾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。该项目致力于开发一种稳定、高性能的流动沸腾系统，以满足当前电子设备的冷却需求。这将通过一种具有锥形歧管的新颖开放微通道设计来实现。开放的微通道设计为蒸汽提供了低阻力通道，而液体仍与基板接触，由于成核和/或对流沸腾而提供有效的冷却。通过在衬底上分别添加偏移带状翅片和纳米线，可以进一步提高传热系数和临界热流密度（安全运行下的最大可能热流密度）。锥形管汇是消除流动沸腾不稳定性的有效途径。这些概念已经在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流动沸腾的基本机制，并显着提高与水的传热性能。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设备冷却的介电流体。乙醇也是一种介电流体，与FC87相比具有更好的传热性能。虽然乙醇是可燃的，但在设计安全冷却系统时，其优越的性能可能会与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，他们将获得进行微观运输过程高级研究的实践经验。本项目的主要成果将是开发一种新型的高热流通量去除系统，了解微尺度流动沸腾过程中的基本传热机制，以及培养本科生和研究生。此外，学生和项目负责人将与当地中学生进行互动。他们将介绍新兴的科学领域，包括先进的传热概念，纳米结构的发展和研究努力，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 （women in Engineering）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.