Melting dynamics and energy efficiency of nano-enhanced phase change material (NePCM) with graphene, Al2O3, and CuO for superior thermal energy storage (TES)

Nano-enhanced phase change materials (NePCMs) have emerged as a promising option for boosting the efficiency of thermal energy storage (TES) systems. This study investigates, through numerical simulations, how the incorporation of nanoparticles such as Al2O3, CuO, and Graphene (with concentrations phi = 0.5 % to 5 %) into paraffin wax affects melting performance. The study further examines how key material properties like thermal conductivity, viscosity, and density influence the overall thermal behavior. Also, the effects of varying cavity inclination angles (theta = 0 degrees to 60 degrees) and heated wall temperatures (Theta = 323 K to 343 K) are analyzed. The computational analysis is carried out using computational fluid dynamics (CFD) and the finite volume method to solve the heat transfer equations. Results indicate that although increased nanoparticle concentrations result in higher viscosity, the improvement in thermal conductivity and the reduction in latent heat outweigh the drawbacks, leading to higher energy storage efficiency. Energy efficiency increases by 4.975 % with the addition of 0.5% Al2O3, while Graphene nanoparticles at a 3% concentration leads to a 7.118 % improvement. The study also shows that increasing the inclination of the cavity angle enhances the melting rate by 43.841 % for pure phase change material (PCM) and 44.865 % for NePCM compared to the horizontal position (theta = 0 degrees). These results demonstrate the potential of NePCMs for improving TES systems and suggest the need for further research to refine NePCM formulations for practical applications in sustainable energy technologies.