Composite phase change materials (CPCMs) are essential components in thermal energy storage systems, but accurately modeling their solid liquid phase change is challenging due to complex thermal behavior caused by anisotropic heat flow, varying thermal and material properties, and thermal contact resistance(TCR) at interfaces. This study presents a unified enthalpy-based lattice Boltzmann method (HLBM), building on the frameworks developed by Huang et al. [1, 2] and the TCR modeling approaches of Feng et al. and Dai et al.[3, 4], to simulate phase change in CPCMs with variable interfacial thermal resistance under realistic conditions. To accurately represent the complex thermal behavior of CPCMs, the model also incorporates anisotropic and spatially varying thermal and material properties, capturing the inherent heterogeneity during phase transitions.  To handle complex geometries, the TCR formulation is extended from flat to curved interfaces using an interpolation scheme. The present HLBM performs with high accuracy when TCRs are negligible and outperforms traditional temperature-based lattice boltzmann models in robustness and stability under large TCRs and high Rayleigh number conditions. Benchmark validations demonstrate excellent agreement with the analytical solution of the Stefan problem for conduction-driven melting in a semi-infinite domain and accurately capture convection-enhanced melting in a 2D cavity across Rayleigh numbers ranging from 10³ to 10⁵. Compared to conventional temperature-based LBM models, the present enthalpy-based LBM demonstrates enhanced numerical stability and accuracy under high thermal contact resistance (TCR) and large Rayleigh number conditions. It also has the capability to incorporate variable interfacial resistance along with spatial variations in the thermal and material properties of CPCMs. This model offers deeper insights into the complex thermal behavior of CPCMs under realistic operating conditions and holds strong potential for guiding the design and optimization of advanced thermal energy storage systems.
 

Composite phase change materials, Interfacial thermal contact resistance, Enthalpy based lattice Boltzmann method