EAGER: Collaborative Research: Feasibility of Self-Propelled Nanoparticles for Heat Transfer Enhancement

许多设备（如计算机）的性能受到从关键组件散热的能力的限制。改进散热技术将使设备更快、更小、更可靠、成本更低。根据该奖项进行的研究将集中在增强传热流体所产生的主动“搅拌”元素的形式，自推进微粒。理论表明，实质性的改进是可能的。如果这些预测能够实现，那么由此产生的技术进步可能会导致数据中心、电动汽车电池、太阳能电池板、医疗设备和其他此类设备设计的变革性改进，每年可能节省数十亿美元的成本。该项目的研究目标是测量在冷却液中添加自推进微粒对传热的影响。一系列的传热测量将获得使用两种不同的设计的自推进微粒，已经被证明产生大量的流体混合和主动湍流。在微搅拌液体的热导率的测量提出了独特的挑战。在这项工作中使用的传热增强的品质因数是有效导热率，其被定义为允许与自推进微粒悬浮液相同的传热速率的虚构停滞液体的导热率。增强在此定义为相对于含有相同颗粒但其自推进运动失活的液体的热导率的有效热导率的增加。将在一系列颗粒直径、速度和体积分数上进行测量，以量化这些参数对有效热导率的影响。实验结果将进行比较，有限元模拟，以方便与现有的理论比较，并确定增强的热流体传输现象。该研究的学术价值在于更全面地了解了流体-颗粒混合物在颗粒推进通过流体的条件下的热流体行为。该奖项反映了NSF的法定使命，并通过使用基金会的学术价值和更广泛的影响审查标准进行评估而被认为值得支持。

The performance of many devices, such as computers, is limited by the ability to remove heat from critical components. Improving heat removal technologies will enable faster, smaller, more reliable, and lower-cost devices. The research conducted under this award will focus on the enhancement of heat transfer fluids resulting from active “stirring” elements in the form of self-propelled microparticles. Theory indicates that substantial improvements may be possible. If these predictions can be realized, the resulting technological advances could lead to transformative improvements in the design of data centers, electric vehicle batteries, solar panels, medical devices and other such devices, potentially leading to cost savings of several billion dollars per year.The research objective of this project is to measure the effect on heat transfer of the addition of self-propelled microparticles to coolant liquids. A series of heat transfer measurements will be obtained using two different designs of self-propelled microparticles that have already been shown to generate bulk fluid mixing and active turbulence. The measurement of thermal conductivity in a microstirred liquid poses unique challenges. The figure of merit for heat transfer enhancement used in this work is the effective thermal conductivity, which is defined as the thermal conductivity of a fictitious stagnant liquid that permits the same heat transfer rates as the self-propelled microparticle suspensions. Enhancement is defined here as the increase in effective thermal conductivity relative to the thermal conductivity of the liquid containing identical particles but with their self-propelled motion deactivated. Measurements will be taken over a range of particle diameters, speeds, and volume fractions to quantify the effect of these parameters on effective thermal conductivity. Experimental results will be compared to finite-element simulations to facilitate comparison with extant theory and identify the thermal-fluid transport phenomena underlying enhancement. The intellectual merit of this research lies in a more comprehensive understanding of the thermal-fluid behavior of fluid-particle mixtures under conditions where the particles propel themselves through the fluid.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.