Cockrell School of Engineering professor Vaibhav Bahadur and his team of researchers have discovered an innovative method to keep ultrahot surfaces cool while consuming low levels of power. The new technology, which utilizes a technique called electrowetting to enable liquid cooling at ultrahigh temperatures, could ultimately result in significant safety and cost-saving benefits for power plants, most of which rely on high temperature steam generation.
The UT Austin technology requires small voltages and consumes very little power compared to the amount of cooling that is provided. The new technology overcomes an existing fundamental limit to liquid cooling and also has better scalability, robustness and performance, which could provide added benefits in other applications like the cooling of high wattage electronics and nuclear reactor operations.
“Electrical voltages are an extremely powerful, efficient tool to boost heat transfer rates and prevent the overheating of surfaces,” said Bahadur, an assistant professor in the Department of Mechanical Engineering at The University of Texas at Austin. “If this technology is applied at a large scale, it could have a tremendous impact on the energy sector.”
The team’s method combats a phenomenon called the Leidenfrost effect, which involves the formation of a vapor gap below a liquid on a hot surface. This insulating vapor gap degrades heat transfer and leads to dryout and the eventual failure of industrial heat transfer equipment, including boiler tubes and steam generators. Liquid cooling thus fails to work at very high temperatures. To solve this problem, Bahadur and his team decided to take a closer look at a technique called electrowetting, which relies on electrical voltages to keep a surface wet.
“It is known that electrowetting will help in getting rid of the vapor gap, and what we discovered was that this works even at very high temperatures. We have demonstrated this at 1000 °F and expect it to work even at higher temperatures” Bahadur said. “The energy-saving benefits of keeping a surface wet at such high temperatures are enormous.”
The insulating vapor layer responsible for the Leidenfrost effect typically reduces the heat dissipation capacity by 100 times. Through the use of electrowetting, the Cockrell School team has shown that the heat dissipation capacity can be increased by at least 10 times.
The picture to the right shows a liquid drop on an ultrahot surface under dryout conditions (surface is starved of liquid). Dryout can be electrically eliminated, as shown in the right image.
This enhancement represents a major advancement in the field of boiling heat transfer. Bahadur and his research team, which includes mechanical engineering doctoral student Arjang Shahriari and undergraduate student Jillian Wurz, published their findings in a recent paper in the journal Langmuir.
