Thermal Conductivity Behavior and Modeling of Microencapsulated Phase Change Material-Modified Cement Composites
Microencapsulated phase change material (MPCM)-modified cement composites have attracted increasing attention for energy-efficient buildings and thermal energy storage applications. Accurate prediction of thermal conductivity is essential for optimizing thermal management performance. However, quantitative understanding of the multiscale heat transfer mechanisms in MPCM-modified cement composites remains relatively limited. In this study, the thermal transport behavior of MPCM-modified cement composites was investigated through experimental characterization and multiscale theoretical modeling. A micro–macro combinatorial accumulation approach was developed based on representative volume element (RVE) construction and cumulative thermal interactions to characterize hierarchical heat transfer mechanisms within the composite system. The proposed model enables quantitative prediction of thermal conductivity for inclusions with different geometries and accumulation states. The results revealed that the proposed MMCA model successfully captured the multiscale evolution of thermal conductivity by considering cumulative RVE effects and inclusion geometrical characteristics. The effective thermal conductivity decreased from 0.802 to 0.519 W/(m·K) as the MPCM volume fraction increased from 0 to 0.217, corresponding to a reduction of approximately 35.3%. Furthermore, the accumulation of RVEs exhibited a rapid reduction followed by stabilization of thermal conductivity, revealing the scale-dependent heat transfer behavior induced by hierarchical inclusion interactions. The main contribution of this work is the establishment of a physics-based multiscale framework that quantitatively links MPCM inclusion characteristics, cumulative thermal interactions, and macroscopic thermal conductivity, providing new insights into the micro-to-macro heat transfer mechanisms of PCM-modified cement composites. This study offers theoretical support for the multiscale design and thermal performance optimization of PCM-modified energy-functional cementitious materials.