Enhancing the thermal energy storage performance of multiphase PCM using triply periodic minimal surface structures

Phase change materials (PCMs) are hindered by low thermal conductivity and the limitation of a single melting point in coping with complex thermal conditions, which significantly constrains the thermal regulation capability and thermal response rate of latent heat thermal energy storage systems. To overcome this bottleneck, this study exploits the triply periodic minimal surface (TPMS) structures, which offer both high specific surface area and spatially independent compartmentalization, to systematically investigate the thermal storage performance of single-phase and multi-phase PCMs under different spatially segregated configurations. The results reveal that, in single-phase systems, elevating the PCM melting point nonlinearly extends the complete melting time; when the melting point is set at 313 K, the latent heat contribution reaches its maximum proportion and the system achieves the highest thermal storage rate. By utilizing TPMS to divide the enclosed space into two independent regions, this study constructs a multi-phase PCM system. The advantage of this system lies in its synergistic functionality: the low-melting-point component enables rapid heat absorption, while the high-melting-point component sustains long-term thermal storage, thereby allowing the system to maintain continuous heat absorption across the entire temperature range. The results indicate that when a single-phase system with a melting point of 324 K is replaced by a multi-phase combination, the heat absorption rates of the P type and G type structures are enhanced by 17.0% and 22.2%, respectively. During the discharge stage, the solidification sequence of the multi-phase system is opposite to that of the melting process, and the total solidification time is primarily governed by the low-melting-point component. Without altering the total heat release, the multi-phase system can effectively modulate the discharge rate by flexibly combining PCMs with different melting points. This study provides important theoretical support for the selection of multi-phase materials and the design of TPMS structures in latent heat thermal energy storage systems.