Beyond water: Physical and heat transfer properties of phase change slurries for thermal energy storage

Thermal energy storage is a key technology for decarbonization. In this context, phase change slurries (PCSs) retain the heat storage advantages of phase change materials (PCMs) while relying on fluidity to overcome heat transfer inefficiencies caused by the poor thermal conductivity of bulk PCMs. PCSs can replace water in conventional low-temperature storage tanks, offering numerous advantages. Despite their potential, there is a lack of research in this area, especially regarding natural convection heat transfer. Furthermore, addressing the complex thermo-physical and rheological properties of slurries is essential. This review focuses on the characterization, measurement, and modeling of physical properties of micro/nano-PCSs and their heat transfer performance under natural convection. The state-of-the-art in the field is presented, research gaps are identified, and directions for future research are proposed. Filling the above gaps will support the choice of PCSs as future and sound enhanced fluids for low-temperature heat storage.