TPMS-based PCM capsules for thermal management in compact electronic systems: Design and evaluation

The increasing power density and transient heat load of compact electronic systems pose critical challenges for thermal management, highlighting the need for effective thermal energy storage (TES) devices as thermal buffers. However, conventional packed-bed TES devices with spherical phase change material (PCM) capsules suffer from poor heat transfer and low space utilization. This study, for the first time, proposes a novel capsule design using triply periodic minimal surface (TPMS) shells to improve both thermal charging performance and PCM packing density. Two TPMS capsule configurations (Case 1 and Case 2), based on the sheet-type I-WP structure, were evaluated and compared with spherical capsules using computational fluid dynamics simulations. Results showed that TPMS-based designs exhibited superior thermal performance. The complete melting time of PCM was reduced by over 70 %, and peak thermal charging power increased by up to 97.2 % compared to spherical capsules. Flow field analysis attributed the improvements to increased heat transfer surface area, more uniform convection, and closer heat transfer distance. However, these advantages came at the cost of higher flow resistance, with pressure drops up to 4.8–5.6 times greater than those in the spherical capsule. Further parametric studies showed that, at low inlet velocity, Case 2 showed better early-stage charging but was later surpassed by Case 1. This crossover occurred earlier as inlet velocity increased. Pressure drop also showed a crossover: Case 2 was more resistive at low flow, while Case 1 incurred higher frictional loss at high flow. These findings offer guidance for compact, efficient TES design in high-power applications.