Performance evaluation of rotational thermal storage tank in energy harvesting and releasing cycle: design of gradient fin structure

To address the issue of low thermal conductivity of phase change materials (PCMs) in energy system applications, this study develops a numerical model to investigate the effects of gradient-height fin configurations on the melting and solidification performance of a rotating TES unit, and compares three types of fin arrangements (uniform, positive-gradient, and negative-gradient). The results indicate that the optimized negative-gradient fin structure significantly accelerates the melting process, reducing the complete melting time by 20.42%. Moreover, it enhances heat transfer in the lower PCM region, improving temperature uniformity by 29.66%. The combination of negative-gradient fins and rotation significantly improves melting efficiency, especially in the upper and middle sections, where velocity field uniformity is improved by 19.98%. In contrast, the positive-gradient configuration exhibits better performance during solidification, as heat dissipation in the upper region is enhanced. This study provides valuable guidance for the design of efficient TES systems.