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Researchers at the University of Texas at Dallas recently conducted tests on a newly developed surface intended for rapid collection and removal of condensates, yielding unexpected results.
The team of mechanical engineers found that their innovative design managed to gather more liquid formed by condensation than their forecasts, which were based on traditional physics models, had suggested.
This discrepancy highlighted a flaw in the existing model and motivated the researchers to propose a new theoretical framework to clarify the observed phenomenon. Their findings were detailed in a paper published on March 13 in the journal Newton.
The implications of this new theory are significant for the development of advanced surfaces intended for energy-efficient water harvesting from the atmosphere.
“This new approach enhances our ability to engineer surfaces that are effective at condensing water and other fluids,” stated Dr. Xianming (Simon) Dai, who is the lead author of the study and an associate professor of mechanical engineering at the Erik Jonsson School of Engineering and Computer Science.
Dai’s research focuses on creating surfaces that can efficiently collect and remove condensed droplets, with potential applications in technologies like water collection and refrigeration.
The core of their new theory pertains to the behavior of rolling droplets—small droplets that detach from a surface during a process known as dropwise condensation. This process is advantageous as it allows surfaces to clear quickly, thereby maximizing the collection of newly formed condensates.
Deepak Monga, a doctoral candidate and research scientist in Dai’s lab, identified that a surface he was experimenting with had regions where droplet formation was not visually apparent. Conventional theories did not account for condensation in such areas.
Upon further examination, the team found that these areas were indeed contributing to condensation, contrary to the predictions of longstanding theories. The droplets formed were just too small to be seen with the naked eye and also reflected the new surface’s efficiency in collecting and removing condensates.
“The key factor is speed. Traditional heat transfer theories overlook how swiftly our new surface can eliminate condensates,” explained Monga, who served as the paper’s lead author. “In our revised model, we integrated the frequency of droplet disappearance to account for the rapid rolling motion.”
Dr. Yaqing Jin, an assistant professor of mechanical engineering, led experiments that visualized the dynamics of tiny water droplets. By employing a sophisticated time-resolved particle image velocimetry system alongside a long-distance microscope, the team was able to document the flow and movement of microscopic particles within droplets.
“This system offers exceptional resolution, allowing us to analyze the velocity and movement patterns of small droplets, thus enhancing our understanding of how these droplets interact with surfaces,” Jin remarked.
Monga has successfully applied the new theoretical insights to design a surface, a study he presented at The American Society of Mechanical Engineers’ 2024 Summer Heat Transfer Conference, where he received the award for best presentation.
This research was supported by various grants, including a Young Faculty Award from the Defense Advanced Research Projects Agency, a Faculty Early Career Development Program (CAREER) award from the National Science Foundation, and funding from the Department of Energy.
Additional co-authors on the paper include mechanical engineering doctoral student Dylan Boylan, research associate Dhanush Bhamitipadi Suresh, Jyotirmoy Sarma, and Dr. Pengtao Wang from Oak Ridge National Laboratory.
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