Thermal characterization of NaNO₃/KNO₃ with different concentrations of Al₂O₃ and TiO₂ nanoparticles

The thermo-physical properties of NaNO₃/KNO₃ (solar salt) added with Al₂O₃ and TiO₂ nanoparticles as phase change material in thermal energy storage system were investigated. Initially the Al₂O₃ and TiO₂ nanoparticles were added to NaNO₃/KNO₃ (60:40) with a concentration of 1%, 3% and 5 mass% using low-energy ball mill. The differential scanning calorimetry instrument is used to measure the thermal properties of the prepared PCM composites. It is found that the phase change temperature and latent heat capacity vary with Al₂O₃ and TiO₂ nanoparticles loading levels. When the loading is not over 3 mass% of Al₂O₃, the phase change temperature drops, and the latent heat capacity increases up to 23.3%. When the loading is over 3 mass% of Al₂O₃, the phase change temperature increases, and the latent heat capacity drops to 14.23%. A significant increase in latent heat capacity is found around 3 mass% of Al₂O₃ loading. When the TiO₂ nanoparticle concentration increases, the phase change temperature decreases, and the latent heat capacity increases up to 32.2%. When the TiO₂ nanoparticle's concentration decreases, the phase change temperature increases, and the latent heat capacity decreases. The thermal conductivity of the composites was found to increase with the increase in the loading of nanoparticles. After adding 3% by mass of Al₂O₃ and TiO₂ nanoparticles, the thermal conductivity was found to increase by 8.30 and 8.10%, respectively. From the characterization studies, we found that TiO₂ helps to achieve the improved thermo-physical properties and heat storage characteristics for NaNO₃/KNO₃ which suggests their potential candidate of usage in the thermal energy storage system.