MIT scientists figured out a way to boil water faster and more efficiently, a discovery that could allow industrial processes to save more energy for things such as electricity-generating plants, chemical production systems, and cooling systems.
The newly-discovered method, which was revealed in a press release by the institution and published on Tuesday, shows how the team tackled the heat transfer coefficient (HTC) and the critical heat flux (CHF).
Efficient Boiling of Water
Generally, there is a tradeoff between the two factors, which are crucial to the boiling process, which means that improving one would tend to make the other worse. A co-author of the study, Youngsup Song, Ph.D., who is a recent graduate, said that both parameters are important. He noted that improving both parameters at the same time is "kind of tricky" because of their intrinsic tradeoff.
Song added that if there were a lot of bubbles on the surface of boiling water, it means that the process was very efficient. On the other hand, if there are too many bubbles on the surface, they can coalesce together, which can form a vapor film over the boiling surface, as per Interesting Engineering.
The vapor film introduces resistance to the heat transfer from the hot surface to the water, with the researchers adding that if the vapor is between the surface and the water, it prevents the heat transfer efficiency and lowers the CHF value.
The team of scientists achieved the process by adding a series of microscale cavities, or dents, to a surface, controlling the way bubbles form on that particular surface. This allowed them to keep the bubbles effectively pinned to the locations of the dents and prevented them from spreading out into a heat-resisting film.
According to SciTechDaily, the finding could help significantly reduce energy use by improving the efficiency of systems that heat and evaporate water. The team made three different kinds of surface modifications, at different size scales, that together account for the increased efficiency.
Saving Energy for Industrial Purposes
Despite the potential benefits of the findings, the team cautioned that the initial results are still at a laboratory scale, and noted that more effort is required to develop a practical, industrial-scale process.
Song, who is now a postdoctoral researcher at Lawrence Berkeley National Laboratory, carried out much of the research as part of his doctoral thesis work at MIT. While the various components of the new surface treatment that Song developed had been studied before, the researchers said that this work is the first to show that the methods could be combined to overcome the tradeoff between the two competing parameters.
The team placed an array of microscale dents on the surface that measured 10 micrometers wide that were spaced roughly two millimeters apart. The surfaces of the dents were also covered in nanoscale ridges, which increase the heated surface area, boosting the rate at which the liquid water evaporates into bubble-forming vapor.
Each dent sits within the top of its own individual tiny pillar, which has a wicking effect, drawing water up to the dent where it continuously forms a layer of liquid between the boiling surface and the bubble. This allowed the researchers to increase boiling efficiency by ensuring that the surface is always heating liquid water, as opposed to passing heat through the vapor in the bubble, New Atlas reported.
Related Article:
New Study Challenges Long-Held Beliefs Regarding Shock-Absorbing Woodpecker Skulls
