UNS: Heat Transfer in Granular Flows: Understanding Similarities and Differences with Molecular Fluids

提出的研究旨在了解为什么流体中的颗粒可能或可能不会增强表面的传热。研究人员将检查模型和实验的结果，以阐明现有的相互矛盾的工作。拟议计划的一部分是让本科生和高中生参与单独的小型研究项目，目标是《不可思议研究年鉴》（AIR）杂志，其编辑委员会包括几位诺贝尔奖获得者。AIR的口号是“让人发笑然后思考的研究”，旨在激励更广泛的学生获得科学研究的经验，同时也为更多的公众提供一种使科学更容易接近和令人兴奋的手段。PI建议开发数值模型并通过实验验证数值模型（以及相关假设），以应用颗粒流在两相流中增强传热。现有文献的实验结果令人困惑地表明，热流不随佩莱特数单调缩放。拟议的研究旨在解决这一矛盾，因此很有趣。这项工作建立在最近涉及多相流的研究基础上，但增加了涉及不同形状、表面粗糙度、滑移速度和流动不稳定性的颗粒的复杂方法。需要验证的假设是：(1)文献中现有数据集的宏观量（传热系数）差异可以追溯到微观特征，如表面粗糙度和层析成像；(2)粒子迁移率的增加可导致与边界接触时间的减少，从而减少传热；(3)流动不稳定性的存在可能会减弱传热，因为颗粒流动性增加，从而减少接触。

The proposed study aims at understanding why particles in fluid might or might not enhance heat transfer for surfaces. The investigator will examine results from models and experiments to shed lights on existing conflicting work. Part of the proposed plan is to engage undergraduates and high school students in separate, small research projects aimed at the magazine Annals of Improbable Research (AIR) with an editorial board that includes several Nobel Prize winners. AIR has a tagline "research that makes people laugh and then think," designed to motivate a broader range of students to gain experience in scientific research, as well as a means for making science more accessible and exciting for the greater public. The PI proposes to develop numerical models and experimentally validate the numerical models (and the associated hypotheses) for application of granular flows in enhancing heat transfer during two-phase flows. The existing experimental results in the literature perplexedly indicates heat flux does not scaling monotonously with Peclet number. The proposed research aims at resolving such a contradiction and is thus intriguing. This work builds on recent research involving multi-phase flows but adds complex approaches involving granules with different shapes, surface roughness, slip velocities, and flow instabilities. The hypotheses to be tested are: (1) the discrepancy in existing data sets in the literature for macro-level quantities (heat transfer coefficient) can be traced to micro-level characteristics, such as surface roughness and tomography; (2) an increase in particle mobility can lead to reduced heat transfer due to reduced contact time with boundary; (3) the presence of flow instabilities may attenuate heat transfer due to increased particle mobility and thus decreased contact.