Shape Optimization for Capsule to Enhance PCM Melting in Thermal Energy Storage System

This study proposes an optimization‐driven capsule design strategy to enhance the melting performance of phase change materials (PESs) in thermal energy storage (TES) systems. Diverging from traditional methods that often rely on experiential design, we formulate and implement a systematic shape‐optimization workflow to generate a previously unreported capsule configuration, with the optimized design obtained using the method of moving asymptotes (MMA). Three capsule geometries—smooth, sinusoidal, and optimized—are investigated via numerical simulations and experimental validation. Relative to the smooth baseline, the optimized capsule shortens the total melting time by 20.9% numerically and 20.5% experimentally, outperforming the sinusoidal capsule. Heat‐transfer analysis reveals that the optimized capsule maintains a higher average heat‐transfer coefficient during the transition stage—12.1 W/(m ² ·K) versus 8.9 and 7.7 W/(m ² ·K) for the sinusoidal and smooth capsules, respectively—indicating improved convective transport persistence. Mechanistically, the performance gain arises not solely from the increased surface‐to‐volume ratio (159 vs. 153 and 148 m ⁻¹ ), but also from curvature‐enhanced and sustained buoyancy‐driven circulation that mitigates boundary‐layer thickening and thermal stratification. The results demonstrate that shape optimization offers a robust and scalable route to high‐efficiency PCM encapsulation, providing a practical design pathway for TES systems requiring rapid thermal response and high energy charging rates.