Thermal behaviors of energy storage process of eutectic hydrated salt phase change materials modified by Nano-TiO2

This paper investigated the thermal behaviors of energy storage process of eutectic hydrated salt phase change materials (EHS PCMs) modified by Nano-TiO 2 , including energy storage efficiency and energy storage density of the sample. The energy storage process of EHS PCMs with different mass fraction of Nano-TiO 2 was divided into three stages – solid-solid stage, solid-liquid stage and liquid-liquid stage. The factors affecting energy storage efficiency and energy storage density at each stage were analysed, and the whole energy storage process was comprehensively evaluated. Before that, the study about SrCl 2 ·6H 2 O as an auxiliary nucleator was carried out to ensure the stability of EHS PCMs. Results show that the synergistic effect of Nano-TiO 2 and SrCl 2 ·6H 2 O could optimize the crystallization of EHS PCMs and reduce the supercooling degree to 1.7 °C. The EHS PCMs with 0.5 wt% Nano-TiO 2 has the highest energy storage efficiency, the energy storage density of EHS PCMs with 0.3 wt% Nano-TiO 2 increased about 10.4% compared to that without Nano-TiO 2 . This attributes to the Nano-TiO 2 in EHS PCMs changes the crystallinity and crystallization morphology of PCMs affecting the latent heat, and the different changes of thermal conductivity and specific heat capacity of the sample occurring in solid and liquid energy storage stages. This experiment provides a macro comprehensive evaluation of energy storage process of EHS PCMs with nanoparticles and explains the change regularity of thermal properties in different energy storage stages, giving a reference for EHS PCMs using nanoparticles. • Thermal behaviors of energy storage process of EHS PCMs modified by Nano-TiO 2 are investigated. • Energy storage efficiency and density are determined by the latent heat, thermal conductivity and specific heat capacity. • The latent heat of EHS PCMs is affected by the crystallinity and crystallization morphology of the sample. • Grain refinement increases the specific heat capacity, but interfacial thermal resistance reduces the thermal conductivity. • Hydrogen bond and thermal conductivity network formed by Nano-TiO 2 and water increases the thermophysical property.