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

这项研究旨在了解为什么流体中的颗粒可能会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，目标是杂志《不可能研究年鉴》（AIR），编辑委员会包括几位诺贝尔奖得主。 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，以及使科学更容易获得和更令人兴奋的手段。PI建议开发数值模型，并通过实验验证数值模型（和相关假设），用于颗粒流在两相流期间增强传热的应用。 已有的实验结果令人困惑地表明，热流密度与Peclet数并不单调成比例关系。 拟议的研究旨在解决这样一个矛盾，因此是耐人寻味的。 这项工作建立在最近的研究，涉及多相流，但增加了复杂的方法，涉及不同形状的颗粒，表面粗糙度，滑移速度和流动不稳定性。待检验的假设是：（1）文献中现有数据集对宏观层面数量的差异（传热系数）可以追溯到微观水平的特征，如表面粗糙度和层析成像;（2）颗粒迁移率的增加可以导致由于与边界的接触时间减少而导致的传热减少;（3）流动不稳定性的存在可能由于增加的颗粒移动性和因此减少的接触而减弱热传递。

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.