Thermal storage performance of phase change material in a cylindrical tank with concave-convex fin configuration

• A concave and convex fin in the storage tank has been designed and performed. • The melting process and the storage energy rate of PCM has been obtained and calculated. • Multi-conditions have been investigated and analyzed. Fin design plays a crucial role in the thermal performance of latent heat storage systems (LHSS), as it directly governs the transfer heat behavior in the storage unit. This work proposes an innovative three-level concave–convex fin architecture designed to improve both temperature uniformity and overall energy storage capacity. The numerical model is validated against comprehensive experimental data. Three arrangement layouts (PA-1, PA-2, and PA-3) are examined under various operating conditions—specifically, for the unit heat transfer fluid (HTF), the HTF inlet temperature and mass flow rate—to evaluate their influence on the melting behavior. Results state that setting the HTF flow rate to 0.187 kg/s shortened the PCM melting time by 39.1% and increased the charging rate by 40.4% for the unit, relative to the minimum flow condition. Likewise, raising the HTF inlet temperature to 368.15 K contribute to a 33.3% reduce in melting time and a 39.8% improvement in average melting rate for the unit compared to the lowest temperature case. The PA-1 pattern, with its alternating concave–convex layout, outperformed the other configurations. This innovative design mitigates the inefficiency of traditional single-sided fins by harnessing synergistic melting between longer and shorter fin sections, thus enhancing natural convection-driven heat transfer. These findings offer valuable guidance for the structural refinement of fins and for deeper insight into phase change behavior in thermal storage systems.