Elucidating the True Role of Surface Microtexturing in Friction Reduction and Enhanced Convective Heat Transfer

这个项目的目标是阐明表面微纹理（粗糙度）对减少摩擦和对流（基于流动）传热的作用。了解微织构的流动行为和传热相互作用将对超疏水（疏水）表面的一般区域产生重大影响，特别是对减少摩擦和热管理的目的。这项研究的结果将对用于电子冷却和便携式生化诊断应用的微观流动系统以及用于气候控制和发电应用的大规模流动系统产生重大影响。该项目还为研究人员教授的课程提供了新的课堂材料，并为小学观众提供了外展活动。东北大学正在为来自STEM领域代表性不足群体的大一和大二学生建立一个本科暑期实习项目，为他们未来在工程领域的职业生涯做好准备。研究和分析了不同润湿程度、气液界面固定和Re条件下表面微观几何内部流动的控制物理特性。一个多任务的研究计划，包括微纹理样品的热液压和光学诊断特性，不同边界条件下的单相和两相流的数值模拟，以及微纹理的微观几何优化。该项目包括以下具体工作：(1)开发实验基础设施，以表征不同润湿和热条件下的压力-流量行为、滑移速度、流体/壁温度和壁热流密度。这些结果正在通过数值模拟和分析进行验证；(2)评价微织构试样在压力和温度作用下不同润湿程度、不同气液界面固定化程度下的减摩特性；(3)表征微织构微通道对流换热的摩擦减少，解决间隙空间热扩散减少和间隙空间摩擦减少导致的热平流增强之间的权衡问题。

The goal of this project is to elucidate the role that surface microtexturing (roughness) has on friction reduction and convective (flow-based) heat transfer. Understanding flow behavior and heat transfer interactions with microtexturing will have significant impact on the general area of superhydrophobic (water repelling) surfaces, particularly for friction reduction and thermal management purposes. The results of this research should have major implications for microscopic flow systems used in electronics cooling and portable biochemical diagnostics applications, as well as larger scale flow systems used in climate control and power generation applications. This project also provides new classroom materials for courses that the researchers teach as well as outreach activities geared towards elementary school audiences. An undergraduate summer internship program aimed Northeastern University freshmen and sophomores from groups that are underrepresented in STEM fields is being established to prepare them for future careers in engineering. The governing physics behind the flow within surface microgeometry for different wetting degrees, gas-liquid interface immobilization, and Re conditions is being studied and analyzed. A multi-task research program is in place that includes thermo-hydraulic and optical diagnostics characterization of microtextured samples, numerical simulations of single and two-phase flow with different boundary conditions, and microgeometry optimization of the microtexturing. The project is comprised of the following specific thrusts: (1) Development of an experimental infrastructure to characterize pressure-flow rate behavior, slip velocity, fluid/wall temperature, and wall heat flux for different wetting and thermal conditions. These results are being validated against numerical simulations and analysis; (2) Assessment of the friction reduction characteristics of the microtextured samples under varying degrees of wetting due to pressure and temperature effects, and under different degrees of gas-liquid interface immobilization; and (3) Characterization of friction reduction on the convective heat transfer of the microtextured microchannels, addressing the tradeoffs between reduced thermal diffusion in the gap space and enhanced thermal advection due to the friction reduction brought about by said gap spaces.