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

许多设备(如计算机)的性能受到关键部件散热能力的限制。改进散热技术将使设备更快、更小、更可靠和更低成本。在该奖项下进行的研究将侧重于由以自推进微粒形式存在的活性“搅拌”元素所产生的强化换热流体。理论表明，可能会有实质性的改善。如果这些预测能够实现，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的设计得到革命性的改进，潜在地每年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。使用两种不同设计的自行式微粒将获得一系列的传热测量，这两种微粒已经被证明可以产生大量的流体混合和活跃的湍流。微搅拌液体中导热系数的测量提出了独特的挑战。本文所用的强化换热优值系数是有效导热系数，它被定义为允许与自行式微粒悬浮液具有相同传热率的虚拟滞留液体的导热系数。这里的增强定义为有效导热系数相对于含有相同颗粒的液体的导热系数的增加，但其自身推进运动被停用。测量范围包括颗粒直径、速度和体积分数，以量化这些参数对有效导热系数的影响。实验结果将与有限元模拟进行比较，以便于与现有理论的比较，并确定增强背后的热-流体传输现象。这项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动自身通过流体的条件下的热-流体行为。这一奖项反映了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，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.