After nearly 25 years of digging deep into surface modification -- the branch of materials science that explores the outer parts of all things solid -- UNLV's Kwang Kim has emerged as a thought leader in developing and deploying a technology that helps condensers at steam-power plants function more efficiently.
The technology, called "dropwise condensation," could one day save power companies millions and lead to decreased electricity costs for consumers around the globe.
Condensation is a familiar part of daily life: Think of water vapor, for example, forming droplets on a cold bottle of soda. At power plants, a similar process occurs at heat-exchanging units called condensers. Here, exhaust steam from electricity-producing turbines condenses into water that is recirculated to a boiler. The boiler heats it and produces steam that's pumped back into the turbines.
But the process isn't perfect. When water molecules adhere to the surface of the condenser's collection tubes they create a thin film of moisture. This "film condensation" tends to make heat transfer less robust than it might be.
Working in collaboration with the Daejeon-based Korea Institute of Energy Research, Kim and his team found that by coating condenser tubes with a water repelling, or hydrophobic, substance they can manipulate the water to form droplets instead film.
"The film is the killer for heat transfer," says Kim, who serves as the Southwest Gas Professor of Energy and Matter in the Howard R. Hughes College of Engineering. "In what we have done, if you look at the surface of the tube, the condensate drops off instead of creating a film. This creates a cost savings for the power plant. You can maintain the size of these drops and transfer more heat. Intrinsically, you will have better power plant efficiency. It all interconnects and makes things quite interesting."
The dropwise condensation method can improve heat transfer by more than 200 percent in some steam-producing environments, says Kim, who is also a fellow with the American Society of Mechanical Engineers. Its wider application, he adds, could even revolutionize the way steam plants are constructed.
In a typical power plant using steam, condensers take up a very large footprint of a building. With Kim's coating, their footprint could shrink to a much smaller size.
NBD Nanotechnologies, a Boston-based venture company, took note of Kim's research nearly two years ago.
"They looked at the entire playground of research and noticed that this guy is always popping up. They said, 'Why don't we visit him?'" Kim recalls. "They knew we had one invention that is quite unique. The industry was ignoring this particular application, and we just happened to put things together in the right context."
One patent application had been filed on the technology, and in January 2014 UNLV finalized the licensing deal. Also, NBD hired Bong June Zhang, a postdoctoral scholar and Kim's former doctoral student who had worked closely on the project. As NBD finalizes the product for commercial use, Zhang will be an important part of the testing process.
"This is a great example of a technology developed at a university finding a great commercial partner to create a product to benefit the public," says Zachary Miles, UNLV's executive director of technology transfer and economic development. "We are excited about this partnership and look forward to working with NBD in the future."
The coating may have other important applications as well. It could be used one day to turn fog into water in countries and regions that lack water resources, could boost the performance of everyday condenser-dependent appliances like refrigerators, or speed the "deicing" of frost-bound passenger planes.
The dropwise method is just one of many discoveries Kim has made during his career. His research interests also encompass a wide spectrum of energy systems and active materials and sensors, blending expertise and concepts from mechanical engineering, physics, biology and more. In his Active Materials and Smart Living Laboratory at UNLV, Kim provides an environment that promotes the acquisition of the skills and attitudes students need to become great innovators.
Among Kim's ongoing projects is an investigation aimed at developing a battery system that uses a unique composite material as part of an electrochemical cell for energy conversion. The device could offer several advantages over conventional batteries: lower maintenance, a longer cycle life, and unlimited scalability of energy capacity. It could be particularly attractive for electric vehicles, for example, since the batteries could be easily -- and almost instantly -- recharged.
Finally, Kim is currently at work on a next-generation "robotic catheter," one using an ionic polymer-metal composite artificial muscle, for use in medical therapy and diagnosis. The National Science Foundation is supporting the project.
Kim has authored and co-authored more than 325 publications, including 148 refereed journal papers and three monographs. His research has been funded by NASA, the U.S. Office of Naval Research, the U.S. Department of Energy, the Army Research Office, the National Science Foundation, private companies, and other organizations.
