Article 6N3RK New Method to Create Aquatic Levitation Has Implications For Cooling Nuclear Reactors

New Method to Create Aquatic Levitation Has Implications For Cooling Nuclear Reactors

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janrinok
from SoylentNews on (#6N3RK)

Arthur T Knackerbracket has processed the following story:

Splash a few drops of water on a hot pan and if the pan is hot enough, the water will sizzle and the droplets of water seem to roll and float, hovering above the surface.

The temperature at which this phenomenon, called the Leidenfrost effect, occurs is predictable, usually happening above 230 degrees Celsius. The team of Jiangtao Cheng, associate professor in the Virginia Tech Department of Mechanical Engineering, has discovered a method to create the aquatic levitation at a much lower temperature, and the results have been published in Nature Physics.

Alongside first author and Ph.D. student Wenge Huang, Cheng's team collaborated with Oak Ridge National Lab and Dalian University of Technology for sections of the research.

The discovery has great potential in heat transfer applications such as the cooling of industrial machines and surface fouling cleaning for heat exchangers. It also could help prevent damage and even disaster to nuclear machinery.

Currently, there are more than 90 licensed operable nuclear reactors in the U.S. that power tens of millions of homes, anchor local communities, and actually account for half of the country's clean energy electricity production. It requires resources to stabilize and cool those reactors, and heat transfer is crucial for normal operations.

For three centuries, the Leidenfrost effect has been a well-known phenomenon among physicists that establishes the temperature at which water droplets hover on a bed of their own vapor. While it has been widely documented to start at 230 degrees Celsius, Cheng and his team have pushed that limit much lower.

The effect occurs because there are two different states of water living together. If we could see the water at the droplet level, we would observe that not all of a droplet boils at the surface, only part of it. The heat vaporizes the bottom, but the energy doesn't travel through the entire droplet. The liquid portion above the vapor is receiving less energy because much of it is used to boil the bottom. That liquid portion remains intact, and this is what we see floating on its own layer of vapor. This has been referred to since its discovery in the 18th century as the Leidenfrost effect, named for German physician Johann Gottlob Leidenfrost.

That hot temperature is well above the 100 degree Celsius boiling point of water because the heat must be high enough to instantly form a vapor layer. Too low, and the droplets don't hover. Too high, and the heat will vaporize the entire droplet.

The traditional measurement of the Leidenfrost effect assumes that the heated surface is flat, which causes the heat to hit the water droplets uniformly. Working in the Virginia Tech Fluid Physics Lab, Cheng's team has found a way to lower the starting point of the effect by producing a surface covered with micropillars.

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