MIT Scientists Invent a Better Way to Boil Water

MIT News has an announcement:The boiling of water or other fluids is an energy-intensive step at the heart of a wide range of industrial processes, including most electricity generating plants, many chemical production systems, and even cooling systems for electronics. Improving the efficiency of systems that heat and evaporate water could significantly reduce their energy use. Now, researchers at MIT have found a way to do just that, with a specially tailored surface treatment for the materials used in these systems.The improved efficiency comes from a combination of three different kinds of surface modifications, at different size scales. The new findings are described in the journal Advanced Materials in a paper by recent MIT graduate Youngsup Song PhD '21, Ford Professor of Engineering Evelyn Wang, and four others at MIT..... "If we have lots of bubbles on the boiling surface, that means boiling is very efficient, but if we have too many bubbles on the surface, they can coalesce together, which can form a vapor film over the boiling surface," Song says. That film introduces resistance to the heat transfer from the hot surface to the water. "If we have vapor in between the surface and water, that prevents the heat transfer efficiency and lowers the critical heat flux value," he says....Adding a series of microscale cavities, or dents, to a surface is a way of controlling the way bubbles form on that surface, keeping them effectively pinned to the locations of the dents and preventing them from spreading out into a heat-resisting film... In these experiments, the cavities were made in the centers of a series of pillars on the material's surface. These pillars, combined with nanostructures, promote wicking of liquid from the base to their tops, and this enhances the boiling process by providing more surface area exposed to the water. In combination, the three "tiers" of the surface texture - the cavity separation, the posts, and the nanoscale texturing - provide a greatly enhanced efficiency for the boiling process, Song says... The nanostructures promote evaporation under the bubbles, and the capillary action induced by the pillars supplies liquid to the bubble base. That maintains a layer of liquid water between the boiling surface and the bubbles of vapor, which enhances the maximum heat flux. While the article stresses it's still a laboratory-scale process (needing more work to become a practical "industry-scale" process), "There may be some significant small-scale applications that could use this process in its present form, such as the thermal management of electronic devices, an area that is becoming more important as semiconductor devices get smaller and managing their heat output becomes ever more important." Wang says in the announcement, "There's definitely a space there where this is really important."The article includes a bizarre-looking video showing how water now boils on their specially treated surface. Thanks to Slashdot reader joshuark for sharing the link!

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