Fabrication and optimization of kaolin/stearic acid composite as a form-stable phase change material for application in the thermal energy storage systems

Abstract

The intended object of this research was to evaluate the influence of different parameters employed on the form-stable phase change materials (FSPCMs) characteristics, with emphasis on the loading percentage of a phase change material (PCM) into the supporting material layers. A melt impregnation process was established to fabricate the FSPCM composites. Stearic acid (SA), one of the fatty acids included in the vegetable oils, possessed various properties suitable as a renewable PCM and was used to be impregnated into kaolin as the supporting material that comes from the clay-based mineral group. Mesh size of kaolin, PCM mass fraction, impregnation time, and temperature were among the studied parameters that took part in the loading percent optimization predicted by the experimental design method of optimization using MINITAB 16. The loading percentage of SA within the kaolin has resulted in a solution method using N-hexane as the solvent of SA. Furthermore, the impact of the parameters interaction on the PCM loading percentage was also studied, and the significant ones were determined. The results of the review and analysis lead to achieving the optimal condition of the experiment with 75%, 260, 100 min, and 130°C for PCM mass fraction, kaolin mesh size, time, and temperature, respectively. Additional characterization procedures were also done on the pre-selected runs to facilitate the explanation for the features of the prepared FSPCMs, PCM, and the supporting material. Various characterization techniques investigated the BET surface area of kaolin, NMR of SA, the morphology, chemical compatibility, and thermal properties of the SA/kaolin composites. The fabricated composite has latent heat of 149.5 J/g with a melting temperature of 60.1°C. The vice versa event (solidifying) requires 143.9 J/g heat dissipation to be solidified at 51.1°C.