N-alkanes have proven to be a new cooling material, environmentally friendly and safe
The traditional refrigerant represented by freon is a powerful greenhouse gas that leads to serious climate problems. Boosted by the excellent cooling performance of plastic crystal materials, barocaloric cooling (BC) has recently received much attention as a promising green refrigeration technology. However, issues such as high driving pressure and poor thermal response remain unsolved, which have hampered their practical applications.
In a new studyPosted in Nature CommunicationScientists led by Professor Tong Peng from Institute of Solid State Physics, Hefei Institutes of Physical Sciences (HFIPS), Chinese Academy of Sciences (CAS), described how they discovered excellent BC cooling performance in the n -alkanes with a self-developed BC test platform, which has provided a new perspective for the development of application-oriented green refrigeration technology.
“It is safe and environmentally friendly,” explained Lin Jianchao, first author of the paper, “and the cost is low. Current cold exploration tends to use solid state phase transition materials. Now we have a future with solid-liquid phase transition (LST) materials in mind. »
The material they found is called n-alkanes. By applying a low pressure of about 50 megapascals, a colossal entropy change of ~700 J kg-1 K-1 was triggered. This is comparable to those of commercial freon-based refrigerants and at least three times higher than reported values of existing BC materials driven by the same pressure. Apart from this, the adiabatic temperature change caused under this pressure also reaches the highest value of the existing BC materials.
In this article, they further revealed the possible mechanism of BC. Raman study and molecular dynamics simulation reveal that applying pressure in the liquid state suppresses torsion and random thermal motions of molecular chains, resulting in lower configurational entropy. When the pressure is strong enough to drive the LST, the configurational entropy will be completely removed and induce the colossal BC effect.
Excellent BC properties, tunable operating temperatures, low cost raw materials, and well-known thermal properties suggest that n-alkanes are promising refrigerants for heat cooling.
“We expect more excellent BC performance by evoking LST materials in the near future,” Jianchao said.
– This press release was provided by the Hefei Institutes of Physical Science, Chinese Academy of Sciences