Study on thermophysical properties of porous aluminosilicate ceramics/hitec melting salt composite phase change material: A thermal storage application

Abstract

Thermal storage has begun to be utilized in the process of solar energy utilization. Given the inherent fluctuations and intermittency of solar energy, phase change thermal storage plays a crucial role in enhancing energy utilization efficiency and promoting energy conservation. A series of novel Hitec salt/porous aluminosilicate ceramic composite PCMs (CPCMs) were synthesized and characterized through a combination of molecular dynamics simulations and experimental studies. Computational models of porous aluminosilicate ceramics (ACs) with varying SiO₂:Al₂O₃ molar ratios were established to calculate the porosity, specific surface area, thermal conductivity, and specific heat capacity of the ceramic matrix. Experimentally, porous ACs were prepared using these same molar ratios by incorporating a pore-forming agent. Ceramic precursors were fabricated from kieselguhr, aluminum hydroxide, aluminum oxide, and soluble starch, followed by sintering at 1250 °C to produce porous ACs. The porosity was measured using the Archimedes displacement method, and the molten Hitec salt was subsequently adsorbed into the ceramic matrix via the melt infiltration method to form CPCMs. The performance characteristics of CPCMs, including specific heat capacity, phase change temperature, latent heat of fusion, thermal conductivity, decomposition point, and microstructure, were evaluated using differential scanning calorimetry, thermal conductivity analysis, thermogravimetric analysis, and scanning electron microscopy. When CPCMs containing 25 wt% soluble starch had an SiO₂:Al₂O₃ ratio of 1:2, their thermal conductivity was 2.11 W/(m·K), while the specific heat capacity (Cp) and latent heat of fusion were 1.25 J/(g·K) and 60.83 J/g, respectively. This study provides a theoretical foundation for selecting appropriate CPCMs in thermal storage systems.