Observation of quasi-equilibrium phase coexistence in supercritical fluids

A protracted-lasting non-equilibrium phase coexistence in supercritical fluids has been noticed by a Korean analysis group.

A group of researchers led by Professor Gunsu S. Yun from POSTECH’s Department of Physics and the Division of Advanced Nuclear Engineering and Professor Dong Eon Kim of the Department of Physics and Max Planck POSTECH/Korea Research Initiative (MPK) has noticed the non-equilibrium phase coexistence in supercritical fluids lasting a number of hours. The researchers defined the phenomenon by way of a mass transport mannequin on the phase coexistence interface, the place the transport happens in chunk of nano-sized clusters as a substitute of single atoms.

It has been accepted as scientific data for about 200 years that when the temperature and strain of a fluid rise above a sure stage known as the critical point, the boundary between liquid and fuel disappears and a change of state not happens. However, within the 2010s, analysis findings reported that supercritical fluids might have liquid or fuel properties relying on temperature and strain situations. Since then, it has been repeatedly confirmed by way of varied experiments and simulations that a number of states exist within the supercritical fluid area. However, the opportunity of a state by which a plurality of phases coexists fairly than a single phase on the identical temperature and strain level—that’s, a state just like that by which a common liquid and fuel coexist after phase separation—has not been mentioned.

To this, the joint analysis group, within the course of of creating a supercritical argon fluid utilizing a high-pressure chamber that operates in successive compression-expansion cycles, demonstrated a state the place a considerable amount of argon droplets (fashioned by adiabatic enlargement cooling) coexist with the gas-like supercritical background whereas sustaining their liquid-like properties. The state the place these two phases coexist in isolation persists a surprisingly very long time and the researchers introduced a brand new mass transport mannequin mediated by nano-clusters—an enchancment on the standard evaporation mannequin—to clarify the phenomenon.

Supercritical fluids are being utilized in varied industries akin to warmth alternate methods in energy vegetation, pharmaceutical processes, semiconductor cleansing, and meals processing due to their helpful properties akin to low viscosity and excessive solubility. The non-equilibrium phase coexistence in supercritical fluids found on this research has a big influence on the bodily and chemical properties akin to warmth capability, thermal conductivity, and viscosity, which can show necessary for supercritical fluid processing in industrial purposes.

In addition, this achievement is of great tutorial worth in that it laid the inspiration for associated analysis by figuring out for the primary time the nonequilibrium phase coexistence of supercritical fluids, which is an unexplored space.

“Research on nonequilibrium of supercritical fluids is not only helpful in industrial processes, but also helpful in understanding various supercritical fluids that exist in the natural world, as in the atmospheres of planets such as Venus and Jupiter, volcanic eruptions, and fluids in the Earth’s crust,” remarked Professor Gunsu S. Yun who participated as a co-corresponding writer within the research. “Our findings will contribute to understanding the transport properties of supercritical fluids.” He added, “We are conducting research to theoretically interpret nonequilibrium phase coexistence in supercritical fluids beyond experimental results.”

The findings from this research had been revealed on July 30, 2021 inNature Communications. The analysis was performed with the assist from the National Research Foundation of Korea and the Max Planck Korea/POSTECH Research Initiative.

Provided by
Pohang University of Science & Technology (POSTECH)