Preparation and properties of NH4Al(SO4)2·12H2O- CH3COONa·3H2O eutectic phase change materials and supercooling modification

Abstract

A eutectic hydrate salt phase change material composed of NH₄Al(SO₄)₂·12H₂O-CH₃COONa·3H₂O was prepared. The eutectic composition, determined experimentally to consist of 92.5 wt% NH₄Al(SO₄)₂·12H₂O and 7.5 wt% CH₃COONa·3H₂O, deviated significantly from predictions made by the Scholar’s equation, highlighting the need for optimization of theoretical prediction methods. The eutectic material exhibited promising thermal storage properties, but a significant supercooling degree of 12.98 K was observed. To mitigate this issue, 14 different nucleating agents were evaluated and five nucleating agents were identified as effective in reducing the supercooling degree to below 1 °C. Furthermore, the thermophysical properties of the eutectic phase change materials with five preferred nucleating agents, including phase change temperature, latent heat, volume expansion ratio and thermal storage density, were characterized using differential scanning calorimetry, T-history, and solid–liquid density testing. Among the five preferred nucleating agents, Nano Cu demonstrated the best performance, achieving a high thermal storage density of 223.45 kJ/kg and a minimal volume expansion ratio of 4.92 %. Future studies will focus on optimizing heat transfer characterization and integrating this material into renewable energy-based heating systems such as heat pumps, solar heating systems, and valley electric heating systems to achieve sustainable and efficient heating solutions.