Enhanced melting behavior of phase change materials using anisotropic Primitive sheet-networks triply periodic minimal surface structure

Triply periodic minimal surface (TPMS) lattices offer great design flexibility. A well-designed lattice effectively enhances the effective thermal conductivity of TPMS composite phase change materials, thereby improving the efficiency of latent heat thermal energy storage systems. In this study, four anisotropic Primitive structures (gamma-10, gamma-2.5, beta-10, and beta-2.5) were obtained by varying cell sizes along the heat flux direction (gamma) and perpendicular to it (beta). Computational fluid dynamics (CFD) simulations were used to investigate the effective thermal conductivity and melting behavior of these structures under isothermal and isoflux conditions. Results indicated that, due to the shortened heat transfer path along the TPMS, gamma-10 and beta-2.5 enhanced effective thermal conductivity by24.8 % and 10.5 %, respectively, compared to the original Primitive. This enhancement led to a 12.5 % reduction in the complete melting time for gamma-10 under isothermal conditions, while maintaining excellent temperature uniformity under isoflux conditions. However, beta-2.5's significant suppression of convective heat transfer offset the increase in effective thermal conductivity, resulting in no reduction in complete melting time. Furthermore, as gamma increased, the complete melting time under isothermal conditions gradually decreased (by 8.0-14.5 %), while temperature uniformity under isoflux conditions improved. These findings provide a promising approach for efficient thermal energy storage applications.