Effect of SWCNT with different length-diameter ratios on the thermophysical properties of molten carbonates: A molecular dynamics study

MY Yang and YT Jia and JT Wang, JOURNAL OF ENERGY STORAGE, 134, 118187 (2025).

DOI: 10.1016/j.est.2025.118187

Carbonate molten salt as the most competitive thermal energy storage medium, being fabricated into nanofluids is currently the primary method to enhance its thermophysical properties. Meanwhile, the shape of nanoparticles plays a crucial role in the thermophysical properties of molten salt-based nanofluids, but the mechanism of its influence remains unclear. In this study, the molecular dynamics simulation method was adopted. Innovatively, the unique one-dimensional tubular structure of SWCNT (keeping the cylindrical shape unchanged) was utilized to precisely control the aspect ratio (L/R), and a carbonate/SWCNT molten salt based nanofluid was constructed. At high temperatures ranging from 1150 K to 1450 K, a systematic study was carried out on the influence of adding 1 wt% SWCNT with different aspect ratios (1.99, 2.42, 3.17, 5.74, 7.98) on the thermophysical properties of molten salt-based nanofluids. By in depth analysis of the evolution of the microscopic structure and energy distribution, the molecular mechanism by which the L/R affects the thermal performance was revealed. The results showed that SWCNT with a larger L/R value can further enhance the thermal properties of the system. In the molten salt-based nanofluid where the SWCNT has a length- diameter ratio of 7.98, the maximum increases in thermal conductivity and specific heat capacity relative to base salt are 7.92 % and 2.78 % respectively. The increase of L/R significantly enlarges the contact area between SWCNTs and molten salt ions. This leads to changes Coulomb potential (Ecoul) and molecular energy (Emol) of the system. It promotes a more compact structure of the interfacial compression layer. This study provides new theoretical basis and design ideas for the targeted improvement of the performance of CSP thermal storage molten salts through the precise design of nanoparticle morphology.

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