Multiscale finite element modeling of macro-encapsulated phase-change material in 3D-Printed concrete walls under Riyadh climatic conditions

Phase-change materials (PCMs) are widely used in building systems to control indoor temperature fluctuations and improve energy efficiency. This study conducts a multiscale finite element investigation of the thermal performance of three-dimensional (3D) printed concrete walls incorporating hollow ceramsite (HC) macro-encapsulated PCM under the climatic conditions of Riyadh. A two-scale modeling approach wherein a concrete/HC-PCM unit cell is used to estimate the effective thermal conductivity of the thermal storage concrete is developed. The predicted values are validated against experimental data from the literature, followed by implementation in dynamic wall-scale simulations. The effects of the HC-PCM volume fraction, PCM melting–solidification temperature, wall infill geometry, and multiple PCM melting ranges on thermal regulation are evaluated. The results indicated that increasing the HC-PCM volume fraction improved thermal regulation; a 0.3 HC-PCM volume fraction reduced the peak inner-wall temperature by ∼1.2 °C compared with the wall without PCM. The PCM transition temperature strongly affected seasonal performance; a 30–32 °C range was the most suitable for summer, whereas lower ranges of 15–17 °C and 18–20 °C were more effective in winter. Among the investigated wall geometries, the diamond infill produced the lowest mean temperature and decrement factor, demonstrating the best thermal damping performance. In addition, using two PCMs with different melting ranges reduced the inner-wall temperature swing by ∼45% compared to that of a single-PCM system. These findings highlight the importance of optimizing PCM properties and printed wall geometry for passive thermal regulation in hot arid climates.