Enhancing thermal storage in a single-tank molten salt system using fins

Thermal stratification and localized overheating limit the charging rate and capacity of single-tank molten salt thermal storage systems driven by single source heaters. To address these challenges, this study is the first to systematically optimize annular fin geometry for single source molten salt heaters under natural convection, aiming to elucidate the coupling mechanism of fin geometry on natural convection heat transfer. A transient three-dimensional computational fluid dynamics (CFD) model based on the fundamental conservation laws was developed and experimentally validated to simulate the single-phase transient heating process. In this work, the effects of fin radial width and fin number on natural convection intensity, plume evolution, and temperature uniformity are investigated. The simulation results reveal that the annular fins effectively disrupt the thermal boundary layer and suppress the rapid ascent of thermal plumes, thereby intensifying fluid mixing at the tank bottom. Parametric analysis demonstrates that, in terms of extending thermal storage duration, increasing the fin number is more effective than increasing the fin radial width. Specifically, the optimal fin configuration (h ring =0.055m, N ring = 9) extended the thermal storage duration by 54.52% compared to the single source heating system, effectively mitigating localized overheating and achieving a significantly more uniform temperature distribution.