Heat transfer characteristics of AlN porous ceramic skeleton/molten salt composite phase change materials for mid-temperature thermal energy storage

A 3D-Ct porous ceramic skeleton was fabricated using photocuring 3D Printing. • The porous ceramic skeleton can accommodate up to 90% molten salt. • The maximum thermal conductivity of the composite PCMs is 2.23 W·m −1 ·K −1 . • The heat storage rate of the composite PCMs can be increased by up to 45.48%. Porous ceramic skeletons exhibit excellent performance in enhancing the heat transfer capacity of molten salt phase change materials (PCMs). However, the low connectivity and structural uncontrollability of their pore struts have limited further improvements in molten salt heat transfer performance. In this study, a three-dimensional continuous Topological (3D-Ct) porous ceramic skeleton with a topological structure was proposed and fabricated by 3D printing coupled with liquid-phase silicon infiltration reaction sintering. The 3D-Ct porous ceramic skeleton/molten salt composite PCMs were prepared using a melt-impregnation method, and their heat transfer performance was investigated both experimentally and numerically. The results showed that the 3D-Ct porous ceramic skeleton provides outstanding heat transfer performance. Compared with pure molten salt PCMs, the 3D-Ct porous ceramic skeleton/molten salt composite PCMs exhibits a 35.31% higher melting rate, a 45.48% increase in heat storage rate, and a 45.50% increase in Nusselt number ( Nu ). In addition, the maximum temperature difference among the measurement points was reduced by 14.3 °C. The numerical simulation results indicate that the 3D-Ct porous ceramic skeleton suppresses heat convection during the phase change of the PCMs, while accelerating PCMs melting and yielding a more uniform overall velocity field. This work proposes a novel structural design strategy for porous ceramic skeletons, overcoming the bottlenecks of low connectivity and poor structural controllability in their pore struts. It also lays a foundation and provides a theoretical basis for the structural design and development of heat energy storage devices.