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MIT team eases surface cooling under extreme heat

Posted: 13 Nov 2013 ?? ?Print Version ?Bookmark and Share

Keywords:MIT? cooling? nanoscale particle? electronic device?

MIT researchers have come up with a way to cool hot surfaces more effectively by keeping droplets from bouncing and turning to vapor in an instant. They were able to do this by decorating the surface with tiny structures and then coat it with particles about 100 times smaller. Using that approach, they produced textured surfaces that could be heated to temperatures at least 100 higher than smooth ones before droplets bounced.

Our new understanding of the physics involved can help people design textured surfaces for enhanced cooling in many types of systems, improving both safety and performance, said Kripa Varanasi, the Doherty Associate Professor of Ocean Utilization in MIT's department of mechanical engineering and the lead author of the study.

The goal for Varanasi and his co-authors, recent MIT PhD recipient Hyuk-Min Kwon and former MIT postdoc J.C. Bird, was to find a way to increase the temperature at which water droplets start bouncing. Past research indicated that rough materials would add more surface area to hold onto the droplets, making it harder for them to bounce. But the research team discovered that not just any rough surface will do.

Through systematic studies using well-defined surfaces, they found that installing microscale silicon posts on a silicon surface raised the temperature at which droplets transitioned from landing to bouncing. But it worked best when the posts were relatively diffuse. As the posts got closer together, the transition temperature gradually dropped until it was no higher than that of a smooth surface.

That result was surprising, noted Bird, who is now an assistant professor of mechanical engineering at Boston University. Common knowledge suggests that the closely spaced posts would provide greater surface area, so would hold onto the droplets to a higher temperature.

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