Chilling Breakthrough: The Perfect Trio to Conquer the Heat

Cooling large, superheated objects present a significant challenge, but a new study from Jonathan Boreyko’s lab at Virginia Tech reveals that the combination of ice, water, and vapor might just be the answer.

Under the leadership of Associate Professor Jonathan Boreyko, the Virginia Tech team has built an impressive body of research centered around ice and water.

Their work spans a range of applications, including de-icing aircraft, developing innovative water harvesting devices, and even crafting snow globes using bubbles.

Their extensive experience with water in various forms has paved the way for their latest project, which demonstrates the remarkable ability of ice to quench heat compared to water alone.

The team’s groundbreaking findings were published in the journal Chem today.

Mojtaba Edalatpour and graduate student Camryn Colón spearheaded this groundbreaking project. Their research focused on exploring techniques for extracting heat from metal, an essential process in fields like metallurgy and firefighting, where rapid temperature reduction is crucial.

In metallurgy, swift cooling is needed to obtain specific material properties, whereas firefighters must act fast to prevent further property damage. However, using water for quenching purposes only works up to a certain temperature threshold; beyond this point, water starts levitating on its vapor, rendering it incapable of dissipating heat effectively.

The team led by Boreyko sought to determine whether employing ice instead of water could overcome the levitation obstacle, potentially allowing them to quench extremely hot surfaces more effectively.

In their experiments, Edalatpour and Colón used a heated aluminum stage to compare the cooling rates of water and ice. To enable a fair comparison, they applied equal amounts of water and ice to the heated surface.

When the initial surface temperature ranged between 100 and 300 degrees Celsius, both water and ice effectively reduced the temperature below 100 C. However, ice accomplished this feat in half the time. For even higher initial temperatures, between 300 and 500 C, ice was the sole successful quencher. At these elevated temperatures, ice’s heat transfer efficiency surpassed that of liquid water by more than 100 times.

So, what made the difference? It all comes down to the unique properties of water, which hinder its ability to efficiently remove heat.

The optimal condition for heat removal is boiling, as the escaping steam in bubbles carries heat away most effectively. However, at high temperatures, water tends to levitate on its vapor, insulating itself from the surface and preventing boiling. Conversely, ice exhibits different behavior. When placed on a hot surface, it absorbs significant amounts of heat while melting, leaving less heat for vapor bubble production and avoiding the levitation issue. As a result, the meltwater boils at a slower rate than pure water, enabling boiling to continue even at high temperatures.

Boreyko compared this peculiar liquid behavior to worker productivity.

“Think about a workaholic who is always focusing on their job,” he added.

“They start off hyper-productive but quickly burn out and become ineffective. It turns out that water is the same way when exposed to ultra-high temperature surfaces: It is so focused and productive at boiling water into vapor that it experiences ‘burnout,’ which is the scientific term for levitation and the catastrophic failure in cooling that results. So ice is like the slow and steady tortoise that wins in the long run. It doesn’t make vapor bubbles very well, but this allows it to keep boiling and avoid levitation when things get heated.”

The team’s hypothesis of utilizing ice for quenching emerged from their recent discovery that ice does not levitate or lose its boiling capacity until it reaches 550 C, as opposed to water’s limit of 150 C. Inspired by these findings, Boreyko’s group embarked on multiple new projects that apply these principles. The published heat transfer study is the first outcome of their efforts.

As part of the ongoing research, Colón is investigating the cooling performance of ice on surfaces maintained at a constant temperature, rather than allowing them to cool down naturally.

“When you have a constant temperature, you can measure the steady-state heat flux, which would allow us to directly compare the heat transfer of ice versus state-of-the-art boilers,” Colón added.

Additionally, the team is exploring ideas for developing a feasible ice-quenching system that can be practically implemented.

“It remains to be seen exactly how to implement three-phase heat transfer for real life applications, but we’re excited to figure it out over the next several years,” Boreyko added. “It might involve making spray nozzles that are able to eject ice particles instead of water, or perhaps it will look more like releasing a pre-formed block of ice onto an overheated surface. There’s a lot more to figure out before this becomes an on-the-shelf technology.”

Image Credit: Virginia Tech