A team of researchers led by Jiangtao Cheng, an associate professor at Virginia Tech Department of Mechanical Engineering, has discovered a method to create aquatic levitation at much lower temperatures than previously thought possible. This phenomenon, known as the Leidenfrost effect, typically occurs at temperatures above 230 degrees Celsius. By designing a surface covered with micropillars that press into water droplets, the team was able to lower the starting point of the effect to 130 degrees Celsius, a significant breakthrough in the field of heat transfer.
The Leidenfrost effect occurs when water droplets hover on a bed of their own vapor due to the high temperature of the surface beneath them. The heat causes the bottom of the droplet to vaporize, creating a layer of vapor that supports the droplet. This effect has been known to start at around 230 degrees Celsius, but Cheng’s team was able to achieve this phenomenon at much lower temperatures by using micropillars on the heated surface. These micropillars are arranged in a regular pattern and help to release heat into the interior of the water droplet, causing it to boil more quickly and leading to levitation and jumping off the surface within milliseconds.
The traditional view of the Leidenfrost effect assumes that the heated surface is flat, causing the heat to hit the water droplets uniformly. However, by using micropillars designed by Cheng’s team, the heat transfer is more efficient, allowing for the effect to be triggered at lower temperatures. This breakthrough has significant implications for various applications, including cooling industrial machines, preventing damage to nuclear machinery, and surface fouling cleaning for heat exchangers. The ability to control the speed of boiling by changing the height of the pillars allows for a more efficient heat transfer process.
In addition to the practical applications of this discovery, Cheng’s team has also found that the interaction between bubbles and droplets in the Leidenfrost effect can provide valuable insights for boiling heat transfer. By investigating how surface structure affects the growth mode of vapor bubbles, the team is able to gain a better understanding of controlling and mitigating the risk of vapor explosions. This is particularly important in industries such as nuclear plants, where surface structure can influence vapor bubble growth and potentially trigger explosions.
Furthermore, the team’s research addresses the challenge of impurities left behind in the textures of rough surfaces, which can pose self-cleaning challenges. Using the micropillars, the generation of vapor bubbles is able to dislodge particles from surface roughness and suspend them in the droplet, allowing for a more efficient cleaning process. Overall, the discovery of a method to achieve the Leidenfrost effect at lower temperatures opens up new possibilities for improving heat transfer applications and preventing disasters caused by overheating machinery.
