Experimental investigations of Alum/expanded graphite composite phase change material for thermal energy storage and its compatibility with metals

A novel composite phase change material(CPCM) were prepared with Aluminum potassium sulfate dodecahydrate(Alum, KAl(SO4)2·12H2O) as PCM and expanded graphite(EG) as nucleating agent and porous matrix for thermal conductivity enhancing. The detailed thermo-physical properties and thermal energy storage performance were studied. The DSC revealed that the melting temperature and latent heat of fusion of Alum/EG CPCM were 87.92 °C and 214.9J/g, respectively. The thermal conductivity of Alum/EG CPCM was improved from 0.497W·m−1·K−1 to 5.875W·m−1·K−1 due to the addition of EG, which can also be confirmed by the infrared thermal imager during charging/discharging process. The Alum/EG CPCM exhibited prominent chemical stability and thermal reliability before and after 500 thermal cycle tests. Furthermore, the corrosion of three metals and one metal alloy were studied and the gravimetric analysis and the results of element composition of four samples exhibited that the brass was the suitable materials for the container for long-term used while stainless steel 304L and aluminum were severely corroded. The results demonstrated that Alum/EG CPCM was a prospective candidate for thermal energy storage and accelerated the research on the Alum/EG heat storage system.