Abstract

MARTINEZ, Franklin R. et al. Experimental evaluation of thermal behavior of Mg(NO₃)₂ based PCMs after addition of nanoparticles for their enhancement. RevActaNova. [online]. 2025, vol.12, n.1, pp.29-39.  Epub Mar 31, 2025. ISSN 1683-0789.  https://doi.org/10.35319/acta-nova.202529.

The use of phase change materials (PCMs) for thermal energy storage (TES) is attractive due to their high-energy storage density within a narrow temperature range. Inorganic PCMs such as salt hydrates and eutectic mixtures are attractive options, although they do have drawbacks like subcooling. This study investigates the addition of commercial nanoparticles in inorganic PCMs to improve the subcooling issue. Specifically, two binary eutectic mixture of Mg(NO3)2·6H2O - NH4NO3 (61.2-38.8wt.%), and Mg(NO3)2·6H2O - MgCl2·6H2O (used as natural bischofite) (50.7-49.3wt.%), and an inorganic commercial SP58 PCM were experimentally tested in a lab-scale shell-and-tube finned thermal energy storage unit. The two eutectic mixtures were doped with 3% of a mixture of nanoparticles of γ-Al2O3 and Mg(OH)2 (50-50wt.%) as additives. All resulting PCMs underwent melting and solidification cycles in a temperature range between 30 °C and 70 °C. Results show that the use of additives reduced the subcooling from 3.5 °C to 2 °C and from 2 °C to 0°C in the case of the Mg(NO3)2·6H2O - NH4NO3 and Mg(NO3) 6H2O - MgCl2·6H2O mixtures, respectively. The commercial PCM exhibited a sub-cooling of 6 °C. Moreover, no clear effect of the additives was observed on the heat transfer rate during melting and crystallization processes, as discrepancies in the results were obtained.

Keywords : Phase change materials; salt hydrates; eutectic mixtures; nanoparticles additives; subcooling; thermal conductivity.

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