Phase transition behaviour of hydrated Glauber's salt based phase change materials and the effect of ionic salt additives: A molecular dynamics study

AS Deepa and A Tewari, COMPUTATIONAL MATERIALS SCIENCE, 203, 111112 (2022).

DOI: 10.1016/j.commatsci.2021.111112

Melting behaviour of inorganic hydrated salts plays an important role in their application as phase change energy storage materials. Particularly, the phase transition temperature and latent heat are determining factors for their application in specific areas for building heating. Ionic salts (e.g. NaCl, KCl) have been proposed as additives to synthesize Glauber's salt with desired phase change properties. However, melting behaviour of the hydrated salts as well as the role of additives is poorly understood, which limits our ability to synthesize these salts with targeted properties. In the present study, classical molecular dynamics simulations were used to study the melting behaviour of pure Glauber's salt. System of NaCl center dot Na2SO4 center dot 10H(2)O was studied to gain insights into the atomistic mechanism of the ionic salt additives. It is observed that the transition of hydrated Glauber's salt into anhydrous Na2SO4 happens over a temperature range due to the stepwise dissociation of water molecules from the parent salt molecule. Addition of NaCl results in lowering the phase transition temperature, while increasing the latent heat of phase change at the same time. Simulation results showed that the hydrogen bonding capacity and ionic charge of the additive salts are the determining factors in altering the phase transition behaviour of hydrated salts. Simulation results showed an excellent agreement with the experimental data available in the literature.

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