Physicochemical Characterization of Phase Change Materials for Industrial Waste Heat Recovery Applications

The recovery and storage of process heat in industrial applications are some of the key factors to improve the sustainability and reliability of high temperature applications. In this sense, one of the main drawbacks is focused on the selection of proper thermal energy storage (TES) materials. This paper performs a full characterization of four phase change storage materials (PCM), KOH, LiOH, NaNO3 and KNO3, which are proposed for storage applications between 270 and 500 degrees C, according to the results obtained through differential scanning calorimeter and thermogravimetric analysis. One of the main innovations includes the corrosive evaluation of these materials in a promising alumina forming alloy (OC4), close to their corresponding phase change temperature during 500 h. The physicochemical properties obtained confirm the optimal use of NaNO3 and KNO3 and recommend the use, with caution, of KOH, due to its higher corrosive potential. FeCr2O4, NiCr2O4 and FeAl2O4 were the main protective spinels formed in the alloy surface, however, the cross-section study in the alloy immersed in KOH, revealed a non-uniform behavior, presenting some cracks and spallation in the surface. On the other hand, the proposal of LiOH was disregarded since it presents a narrow operation temperature range between melting and solidification point.