Preparation and thermal performance of phase change material with high latent heat and thermal conductivity based on novel binary inorganic eutectic system

To manipulate the melting temperature of phase change material for more flexible match with practical applications, two eutectic mixtures of BHO (barium hydroxide octahydrate)-KCl and BHO-KNO3 were investigated as novel binary inorganic eutectic system in this study. Given that the latent heat of BHO-KNO3 eutectic mixture was higher than that of BHO-KCl eutectic mixture, then BHO-KNO3/EG (expanded graphite) composite phase change material (CPCM) with high thermal conductivity was fabricated by melting impregnation method. The thermal properties and performance were assessed using differential scanning calorimeter, thermogravimetry analyzer and thermal conductivity test. The crystalline structure and morphology were revealed by X-ray diffraction and scanning electron microscopy. These results revealed that the two eutectic mixtures still possessed high latent heat more than 200J/g when containing 10 wt% KCl and 12 wt% KNO3, respectively. In light of the similar melting temperatures of the two eutectic mixtures, it could be concluded that melting point altering was related to K+. It was worth noting that for BHO-KNO3/EG composite phase change material, EG not only improved the thermal conductivity up to 7.27 W.m(-1).K-1 as an excellent heat transfer enhancement filler, but also reduced the supercooling degree by 7.6 degrees C as an effective nucleation-site provider.

Automated summary

In this study, two eutectic mixtures of BHO-KCl and BHO-KNO3 were investigated as novel binary inorganic eutectic system to manipulate the melting temperature of phase change material for practical applications. The BHO-KNO3/EG composite phase change material showed improved thermal conductivity and reduced supercooling degree, making it a promising option for thermal energy storage systems. The results indicated that the melting point alteration was related to the presence of K+, and the addition of expanded graphite enhanced heat transfer efficiency.