Researchers at Oregon State University use new technology to control the formation and release of bubbles. Here that technology is illustrated with the letters “OSU” printed on a substrate. Credit: Image courtesy of Oregon State University
Engineers at Oregon State University have found a new way to induce and control boiling bubble formation, that may allow everything from industrial-sized boilers to advanced electronics to work better and last longer. The concept could be useful to either to boil water and create steam more readily, like in a boiler or a clothing iron; or with a product such as an electronics device to release heat more readily while working at a cooler temperature.
“One of the key limitations for electronic devices is the heat they generate, and something that helps dissipate that heat will help them operate at faster speeds and prevent failure,” said Prof, Chang. “The more bubbles you can generate, the more cooling you can achieve. “On the other hand, if you want to create steam at a lower surface temperature, this approach should be very useful in boilers and improve their efficiency. We’ve already shown that it can be done on large surfaces and should be able to scale up in size to commercial use.”
Heterogeneous surfaces structures to tailor bubble nucleation. SEM images of (a), Uniformly dense ZnO nanostructures. (b) 150–500 μm heterogeneous surface configuration. (c) Plain polymer dot, 150 μm in diameter. (d) Cross-sectional area of interface between ZnO nanostructures and polymer dot. (e) Schematic of downhill capillary wicking mechanism on the heterogeneous surface. The downhill scheme promotes the flow of liquid to the lower-level polymer site where nucleation has occurred to efficiently lift-off bubbles and allow for subsequent bubble nucleation.
The new approach is based on the use of piezoelectric inkjet printing to create hydrophobic polymer “dots” on a substrate, and then deposit a hydrophilic zinc oxide nanostructure on top of that. The zinc oxide nanostructure only grows in the area without dots. By controlling both the hydrophobic and hydrophilic structure of the material, bubble formation can be precisely controlled and manipulated for the desired goal.
It allows researchers to control both boiling and condensation processes, as well as spatial bubble nucleation sites, bubble onset and departure frequency, heat transfer coefficient and critical heat flux for the first time.
In electronics, it has apps with some types of solar energy, advanced lasers, radars, and power electronics – anywhere it’s necessary to dissipate high heat levels. In industry, a significant possibility is more efficient operation of the steam boilers used to produce electricity in large electric generating facilities.
http://oregonstate.edu/ua/ncs/archives/2016/may/engineers-create-better-way-boil-water-%E2%80%93-industrial-electronics-applications
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