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 â€œstirringâ€ 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.