Jumping drops are boosted by gravity

10 years ago, a new idea was introduced in the general scientific community: the elimination of water condensers has proven more effective by using surface tension to make "jump" microscopic water droplets. The idea has taken the community of researchers by storm.

"In the last ten years, since I've discovered jumping droplets, the debate is using gravity versus jumping over obstacles," said Jonathan Boreyko, an assistant professor of mechanical engineering at the College of Engineering.

The problem was that because the jump itself was taking place regardless of the severity, what happened after the jump was not taken into account. Five years after his original article, Boreyko returned to the laboratory to discover that to be effective, jumping and gravity should not be mutually exclusive. Now in an article published in the newspaper JouleBoreyko and PhD student Ranit Mukherjee began to examine the orientation of the surface and found that by using vertical condensers, the combination of superhydrophobic surfaces and gravity produced a capacitor at least twice more efficient.

Using superhydrophobic surfaces, featuring nano-pillars and a hydrophobic coating, water droplets can release the power of surface tension whenever two or more drops touch and join, for detach from the surface, regardless of the orientation of this surface. However, not all droplets make a clean getaway.

"Some droplets do not jump or fall to the surface," Boreyko said. "These droplets can then join with each other and form a buildup of condensation that covers the condenser and limits its cooling capacity.For these large droplets, where the jump has failed, draining them by gravity would be an excellent assurance."

Historically, condensers were always oriented vertically to allow water to flow by gravity. However, researchers studying droplets fed by surface tension mainly studied the phenomenon of jumps on flat surfaces and did not talk about the importance of orientation.

"The researches were so focused on the use of surface tension to eliminate droplets instead of gravity, that no one considered that it was not a problem." a "or" situation, "said Boreyko. "It turns out that surface tension and gravity work much better together than one or the other does not work alone."

"What we found shows that there is a unique and optimal way to dissipate the moisture of condensers, which increases the efficiency of various elements, including power plants, or all that. that requires heat exchange, "said Mukherjee.