Molecular dynamics simulation of heat, mass and phonon transport performances of nanoparticle enhanced Na2SO4•10H2O

WD Huang and GB Zhou, JOURNAL OF MOLECULAR LIQUIDS, 397, 124157 (2024).

DOI: 10.1016/j.molliq.2024.124157

Nanoparticles are widely used to prepare nanocomposite phase change materials for higher thermal conductivity (TC). To elucidate the enhancing mechanism of Cu nanoparticles in salt hydrate phase change materials, molecular dynamics simulations are employed to investigate the TC, diffusion coefficient, especially the phonon density of states (PDOS) of pure SSD (sodium sulfate decahydrate) and NSSD (nanoparticle- enhanced SSD). Due to the complex structure of SSD - consisting of two types of ions and water molecules, not only the PDOS of the whole system, but also the PDOS of each component in SSD are separately calculated to reveal the internal phonon transport relationships. The results show that, compared with the pure SSD, the TC of NSSD with 5.94-24.57 wt% Cu nanoparticles increases by 8.19% to 28.73%, while the mass transfer rate decreases by 31.60% to 69.86% due to the increase of the distances between atoms. Furthermore, dispersed Cu nanoparticles may lead to a decrease in TC by 2.64-4.91% by comparison with the single Cu nanoparticle. Prominently, Cu nanoparticles can not only centralize the PDOS of components, but also increase the proportion of PDOS in low frequency for components; meanwhile, the average phonon resonances of Na+/SO42-, SO42- /H2O and Na+ /H2O are promoted by 5.1%, 15.2%, and 26.0%, respectively. It is suggested that the reduction of phonon scattering as well as enhancing phonon resonance between different components is an important mechanism for increasing TC. Moreover, the addition of Cu nanoparticles will reduce the Debye temperature of the system. This work reveals the variation mode of phonon distributions in the SSD lattice caused by the addition of Cu nanoparticles, which helps to understand the relationship between nanoparticle-enhanced heat transfer and phonon transport in salt hydrate PCMs.

Return to Publications page