Mechanism study on the synergistic coupling of the double-dish solar latent heat storage system to enhance heat transfer

With the rapid advance of the global economy, latent heat storage (LHS) is critical to solar thermal utilization. In this study, a double-dish solar Stirling LHS power generation system was designed. The heat transfer performance of the thermal storage system was improved by using the gradient tree-shaped fins and adding graphene nanoparticles to paraffin. Two-dimensional numerical models of three thermal storage systems were developed to study the effects of natural convection and graphene nanoparticle concentration on the melting characteristics of paraffin. From the perspective of field synergy, the coupling effect of fin structure and graphene nanoparticle concentration on the heat transfer process was analyzed. The results show that natural convection exerts an important role in the heat transfer characteristics of paraffin melting. Compared with the six-longitudinal and snowflake fin structures, the gradient tree-shaped fin structure shows a 52.13% and 27.73% reduction in the complete melting time and a 52.16% and 9.53% increase in thermal storage efficiency. Little variation is observed in the liquid phase rate and the average temperature of the composite phase change materials (PCMs) with different concentrations of graphene nanoparticles. The total thermal storage capacity of composite PCMs is higher than that of pure paraffin. The synergistic coupling of gradient tree-shaped fin arrangement and graphene nanoparticles added in paraffin can enhance heat transfer