To Chill, Just Squeeze

Scientists in Japan have developed a new type of refrigeration that generates a liquid-to-gas transition when a nanosponge is squeezed.

AsianScientist (Jul. 11, 2019) – A research team from Tohoku University, Nissan Motor Co., Shinshu University and Okayama University have discovered how to use a nanosponge to carry out liquid-to-gas phase transitions. Their findings, published in Nature Communications, could lead to more efficient refrigerants with a smaller carbon footprint.

Refrigeration systems are widely used in air conditioners and refrigerators. Conventional systems use hydrofluorocarbons as a refrigerant. Unfortunately, hydrofluorocarbons are super pollutants, with a Global Warming Potential about 1,300 times higher than that of carbon dioxide.

Instead of a refrigerant, researchers have figured out how to use force for cooling. When a normal wet sponge is squeezed, water comes out. However, when using a nanosponge with a pore size of under 10 nanometers, a different phenomenon occurs and the sponge retains its liquid. What happens is that the liquid pushed out from the nanosponge immediately evaporates into gas. As the sponge returns to its natural shape, it adsorbs the gas as a liquid into the nanopores again.

Until now, researchers have not carried out the squeezing process of nanoporous materials because conventional materials are too hard to be deformed. The team circumvented this problem by creating their own soft, elastic, nanoporous materials consisting of a single-layer of graphene walls. They measured their results using home-made equipment designed to monitor liquid-gas phase transition when mechanical force is applied.

Until now, there were only two methods of converting trapped liquid into gas: heating or decreasing the gas-phase pressure. The squeezing method provides a third way, generating a new theme in the field of physical chemistry and paving the path for more environmentally friendly refrigeration systems.

The article can be found at: Nomura et al. (2019) Force-driven Reversible Liquid–gas Phase Transition Mediated by Elastic Nanosponges.


Source: Tohoku University; Photo: Hirotomo Nishihara.
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