Using ice to boil water: Researcher makes heat transfer discovery that
expands on 18th century principle

Date:
January 21, 2022
Source:
Virginia Tech
Summary:
Scientists have made a discovery about the properties of water that
could provide an exciting addendum to a phenomenon established
over two centuries ago. The discovery also holds interesting
possibilities for cooling devices and processes in industrial
applications using only the basic properties of water.



FULL STORY ========================================================================== Associate Professor Jonathan Boreyko and graduate fellow Mojtaba
Edalatpour have made a discovery about the properties of water that
could provide an exciting addendum to a phenomenon established over two centuries ago. The discovery also holds interesting possibilities for
cooling devices and processes in industrial applications using only the
basic properties of water.

Their work was published on Jan. 21 in the journal Physical Review Fluids.


========================================================================== Water can exist in three phases: a frozen solid, a liquid, and a gas. When
heat is applied to a frozen solid, it becomes a liquid. When applied to
the liquid, it becomes vapor. This elementary principle is familiar to
anyone who has observed a glass of iced tea on a hot day, or boiled a
pot of water to make spaghetti.

When the heat source is hot enough, the water's behavior changes
dramatically.

According to Boreyko, a water droplet deposited onto an aluminum plate
heated to 150 degrees Celsius (302 degrees Fahrenheit) or above will no
longer boil.

Instead, the vapor that forms when the droplet approaches the surface will become trapped beneath the droplet, creating a cushion that prevents the
liquid from making direct contact with the surface. The trapped vapor
causes the liquid to levitate, sliding around the heated surface like
an air hockey puck.

This phenomenon is known as the Leidenfrost effect, named for the German
doctor and theologian who first described it in a 1751 publication.

This commonly accepted scientific principle applies to water as a liquid, floating on a bed of vapor. Boreyko's team found themselves wondering:
Could ice perform in the same way? "There are so many papers out there
about levitating liquid, we wanted to ask the question about levitating
ice," said Boreyko. "It started as a curiosity project. What drove our
research was the question of whether or not it was possible to have a three-phase Leidenfrost effect with solid, liquid, and vapor." Going into
the ice Curiosity sparked the first investigation in Boreyko's lab some
five years ago in the form of a research project by then-undergraduate
student Daniel Cusumano. What he observed was fascinating. Even when
the aluminum was heated above 150 C, the ice did not levitate on vapor
as liquid does. Cusumano continued raising the temperature, observing
the behavior of the ice as the heat increased. What he found was that
the threshold for levitation was dramatically higher: 550 C (1022 F)
rather than 150 C. Up until that threshold, the meltwater beneath the
ice continued to boil in direct contact with the surface, rather than
exhibit the Leidenfrost effect.



==========================================================================
What was going on underneath the ice that prolonged the boiling? The
project was picked back up by graduate student Mojtaba Edalatpour a
short time later, to solve the mystery. Edalatpour had been working with Boreyko to develop novel methods of heat transfer and put that knowledge
to work in approaching this problem. The answer turned out to be the temperature differential in the meltwater layer beneath the ice. The
meltwater layer has two different extremes: Its bottom is boiling,
which fixes the temperature at about 100 C, but its top is adhered to
the remaining ice, which fixes it at about 0 C.

Edalatpour's model revealed that the maintenance of this extreme
temperature differential consumes most of the surface's heat, explaining
why levitation was more difficult for ice.

Boreyko elaborated. "The temperature differential the ice is uniquely
creating across the water layer has changed what happens in the water
itself, because now most of the heat from the hot plate has to go
across the water to maintain that extreme differential. So only a
tiny fraction of the energy can be used to produce vapor anymore."
The elevated temperature of 550 degrees Celsius for the icy Leidenfrost
effect is practically important. Boiling water is optimally transporting
heat away from the substrate, which is why you feel ample heat rising
from a pot of water that is boiling, but not from a pot of water that is
merely hot. This means that the difficulty in levitating ice is actually
a good thing, as the larger temperature window for boiling will result
in better heat transfer compared to using a liquid alone.

"It is much harder to levitate the ice than it was to levitate the water droplet," said Boreyko. "Heat transfer plummets as soon as levitation
begins, because when liquid levitates, it doesn't boil anymore. It's
floating over the surface rather than touching, and touching is what
causes it to boil the heat away. So, for heat transfer, levitation is
terrible. Boiling is incredible." Using ice for heat transfer As the
team explored possibilities for practical application, they looked to
their existing work. Since Edalatpour had extensive research in heat
transfer, that topic became a logical fit.



==========================================================================
Heat transfer comes most into play for cooling off things like computer
servers or car engines. It requires a substance or mechanism that can
move energy away from a hot surface, redistributing heat quickly to
reduce the wear and tear on metal parts. In nuclear power plants, the application of ice to induce rapid cooling could become an easily-deployed emergency measure if power fails, or a regular practice for servicing
power plant parts.

There are also potential applications for metallurgy. To produce alloys,
it is necessary to quench the heat from metals that have been shaped in
a narrow window of time, making the metal stronger and less brittle. If
ice were applied, it would allow heat to be offloaded rapidly through
the three water phases, quickly cooling the metal.

Boreyko also foresees a potential for applications in firefighting.

"You could imagine having a specially made hose that is spraying ice chips
as opposed to a jet of water," he said. "This is not science fiction. I
visited an aerospace company that has an icing tunnel and they already
have this technology where a nozzle sprays out ice particles as opposed
to water droplets." With myriad possibilities, Boreyko and Edalatpour
are excited about the new contribution that has come to the science
world. Looking back over the past five years, they still credit this
exciting development to their shared spark of curiosity and the drive
to be creative in research.

========================================================================== Story Source: Materials provided by Virginia_Tech. Original written by
Alex Parrish. Note: Content may be edited for style and length.


========================================================================== Related Multimedia:
* Slow-motion_video_as_ice_becomes_water_and_water_levitates ========================================================================== Journal Reference:
1. Mojtaba Edalatpour, Daniel T. Cusumano, Saurabh Nath, Jonathan B.

Boreyko. Three-phase Leidenfrost effect. Physical Review Fluids,
2022; 7 (1) DOI: 10.1103/PhysRevFluids.7.014004 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220121124832.htm

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