Colloquium Series: Let droplets drop the temperature – Droplet-based heat transfer applications (Dr. Patricia Weisensee, Washington University in St. Louis)

Join us on Zoom for our Colloquium Series. Dr. Patricia Weisensee from Washington University in St. Louis will be joining us to present “Let droplets drop the temperature – Droplet-based heat transfer applications.”

Abstract:

We experience and rely on droplets almost every single day of our lives: some more obvious (the shower in the morning, the rain on our way to work, printing at work, etc.), some less (atmospheric water harvesting, thermal management & power generation, materials manufacturing and processing). Yet we hardly ever think about them – take them for granted. In this talk I will show that droplets aren’t only ubiquitous in both nature and industrial processes, but also a complex and fascinating research subject that still holds many mysteries to be solved. In my research group, we are especially interested in the coupling of fluid dynamics, heat transfer, and phase change (condensation or evaporation) during the interaction with solid surfaces.

In this presentation, I will introduce two examples of such interactions: 1) droplet impact and evaporation dynamics on heated surfaces, and 2) dropwise condensation on so-called lubricant-infused surfaces. Using a combination of advanced imaging techniques, ranging from high-speed optical and infrared (IR) imaging to high-speed interferometry and scanning confocal fluorescence microscopy, we study the interplay of droplet dynamics and heat transfer in these systems. For example, I will show that water condensation on the lubricant-infused surfaces can lead to significantly increased water collection rates due to an extremely high droplet mobility compared to bare metal surfaces. Lubricant wetting ridges surrounding droplets introduce an attractive capillary force, leading to self-propelled and gravity-independent droplet motion, which efficiently clears the surface for frequent re-nucleation. On the other hand, wettability-patterning a surface and thus restricting the mobility of droplets can be advantageous during quasi-static droplet evaporation. Interestingly, when droplets impact a heated surface, the creation of additional contact lines, either through wettability-patterning the surface or the formation of an entrapped air bubble, does not significantly alter the heat transfer performance. Instead, convection (at early times) and conduction (at later times) dominate heat transfer.

Biography:

Dr. Patricia Weisensee is an Assistant Professor of Mechanical Engineering and Materials Science at Washington University in St. Louis (WashU). She earned her PhD in Mechanical Engineering from University of Illinois at Urbana-Champaign in 2016. She received a Diplom-Ingenieur in Mechanical Engineering from TU Munich in 2013 and also holds a M.S. in Materials Sciences from University of Illinois at Urbana-Champaign (2011). For her Diplom thesis on condensing steam bubbles in sub-cooled flow, Dr. Weisensee received the Siemens Energy Award 2014. She is an alumna of the German National Academic Foundation (“Studienstiftung des deutschen Volkes”), Germany’s largest, oldest, and most prestigious scholarship foundation.

At WashU, Dr. Weisensee leads the Thermal Fluids Research Group, which focuses on understanding the interplay of fluid dynamics and heat transfer of droplets and other multi-phase systems. Practical applications of interest are phase change heat transfer for thermal management, thermal storage, and water harvesting, metallic additive manufacturing, and droplet interactions with natural systems. To fundamentally study these thermal-fluidic interactions, her group combines multiple experimental techniques, such as high-speed optical and infrared (IR) imaging, interferometry, confocal fluorescence microscopy, and probe-based heat transfer measurements. Dr. Weisensee is a recipient of the NSF CAREER award, the ACS Petroleum Research Fund Doctoral New Investigator grant, and the prestigious NASA Early Career Faculty Award. In recognition of her contribution to the advancement of thermal fluid sciences, Dr. Weisensee received the 2020 ASME ICNMM Outstanding Early Investigator Award and for her dedication to education the St. Louis-wide 2020 Emerson Excellence in Teaching award.

To register, please contact Melissa Gammon at mkgammon@email.UNC.edu.