<p>The addition of fins to Latent-Heat Thermal Energy Storage (LHTES) units enhances heat transfer but may simultaneously suppress the natural convection of liquid phase change material (PCM), creating a design conflict that is often overlooked in conventional uniform fin arrangements. To address this, the present study proposes a novel non-uniform fin distribution strategy characterized by “sparse in the upper region and dense in the lower region” within a shell-and-tube LHTES unit. This design aims to synergistically utilize natural convection in the upper zone and enhanced conductive heat transfer in the lower zone. A two-dimensional numerical model employing the enthalpy-porosity method is established to investigate the melting characteristics of RT35 under four distinct fin arrangement modes with identical fin numbers. The results demonstrate that merely altering the circumferential distribution of fins can significantly intensify natural convection, thereby markedly affecting the overall melting rate. Mode 3, which embodies the proposed non-uniform strategy most effectively, achieved the shortest melting times, reducing the 3/4, 7/8, and 15/16 melting times by 3.00%–10.51%, 3.42%–18.92%, and 6.58%–22.70%, respectively, compared to other modes. This work systematically elucidates the mechanism by which fin arrangement modulates the coupled heat transfer of conduction and convection, providing a practical design principle for optimizing fin layouts in LHTES units.</p>