Effect of particle size on the thermal conductivity of organic phase change materials with expanded graphite

Numerous studies have been conducted to enhance the thermal conductivity of phase change materials (PCMs) using various techniques. Among them, adding high-conductive particles, such as expanded graphite (EG). Nevertheless, in the published literature, there is limited information about the impact of particle sizes on the thermophysical properties of the PCM. This work aims to investigate the impact of two particle sizes of EG (20 and 200 μm) on three commercial PCMs, RT62HC, RT64HC and OM65, using different characterisation techniques, including differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and thermal conductivity measurements. The results indicated that the thermal conductivity of PCMs increases by incorporating the high-conductive particles. The highest thermal conductivity enhancement (156 %) was obtained for the composite PCM based on RT62HC with 6 wt% of 200 μm EG. It could be highlighted that the solid thermal conductivity results are better with particles of 20 μm in paraffin (RT64HC) and with particles of 200 μm in fatty acids (RT62HC and OM65).