LiNO3/NaCl nanocapsules with high thermal properties for medium-temperature thermal energy storage

The use of molten salts as phase change materials (PCMs) for medium temperature thermal energy storage is common. However, these materials are associated with limitations, including leakage during the phase change process , low thermal conductivity , and low moisture resistance for specific types of molten salts such as LiNO 3 /NaCl. This research focuses on the preparation and properties of LiNO 3 /NaCl nanoencapsulated phase change materials (NEPCM). Through detailed analysis using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), we confirmed the successful encapsulation of the PCM and the presence of spherical nanocapsules . Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) results indicated that the encapsulation process did not alter the crystal structure of the PCM. Differential scanning calorimetry (DSC) revealed that the NEPCM exhibited a phase change temperature of 222.4 °C and a latent heat of fusion of 228.7 kJ/kg. Furthermore, the NEPCM demonstrated a high thermal reliability of 99.7 % after fifty thermal cycles, indicating excellent cyclic stability. Moisture resistance experiments were carried out by subjecting both the PCM and NEPCM to a humid environment . The results showed that encapsulation effectively reduced water absorption in the PCM. Thermal conductivity measurements of the nanocapsule suspension were conducted using the Hot Disk method, which indicated an approximate 16.3 % increase in thermal conductivity compared to the base fluid. Additionally, the addition of 2 % MgO to the nanocapsule suspension further enhanced the thermal conductivity by 31.7 %, while maintaining the dispersion stability of the suspension. These enhancements in properties are advantageous for the practical application of the NEPCM as a PCM for thermal energy storage. The overall results demonstrate that nanoencapsulation offers significant improvements in the thermal reliability, moisture resistance, and thermal conductivity of molten salt PCMs, thus broadening their potential applications in medium temperature thermal energy storage systems .