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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?

By analyzing the physics involved, the researchers concluded that closely spaced posts do provide more surface area to anchor the droplets, but they also keep the vapor that forms from flowing. Trapped by adjacent posts, the accumulating vapor layer under a droplet builds up pressure, pushing the droplet off. When the force of the vapor exceeds the attractive force of the surface, the droplet starts to float.

Bringing the posts closer together increases surface interactions, but it also increases resistance to the vapor leaving, Varanasi stated.

To decouple those two effects, the researchers coated the surface featuring spaced-out microscale posts with nanoscale particles. This micro-nano surface texture provides both the extensive surface area of the tiny particles and the wide spacing of the posts to let the vapor flow.

Experiments confirmed their approach. When they sprayed water on their micro-nano surfaces at 400-the highest temperature their experimental setup could provide the droplets quickly wet the surfaces and boiled. Interestingly, under the same conditions, the droplets did not wet the surfaces of samples with either the microscale posts or the nanoscale texture, but did wet the surfaces of samples with both.

In addition to nuclear safety systems, this work has important implications for systems such as steam generators, industrial boilers, fire suppression and fuel-injected engines, as well as for processes such as spray cooling of hot metal. One application now being considered by Varanasi and his colleagues is electronics cooling. The heat fluxes in electronics cooling are skyrocketing, Varanasi added. It might be a job for efficient spray cooling-if they can figure out how to fit a system into the small space inside electronic devices.

The research was supported by a Young Faculty Award from the Defense Advanced Research Projects Agency, the MIT Energy Initiative and the MIT-Deshpande Center.

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