Numerical analysis of 3D-printed concrete envelopes with micro-encapsulated phase change materials (MPCMs) for thermal control

This study extends numerical analyses of 3D-printed cementitious walls incorporating microencapsulated phase change materials (MPCMs). Two wall configurations are examined to assess the combined effects of conduction, natural convection, and surface radiation, with particular attention to emissivity-driven radiative heat transfer. A finite-element CFD model is developed, using thermophysical properties derived from experimental data and homogenised via a three-phase Maxwell-Eucken scheme. Natural-convection predictions are validated against benchmark measurements. A parametric analysis, varying wall geometry and MPCM content, evaluates their influence on thermal performance under Mediterranean summer conditions. Key performance indicators, including periodic transmittance, temperature damping, time lag, and latent-energy storage, are computed. Results show that MPCM content is the dominant factor governing thermal evolution in time, whereas divider geometry has only a minor impact because cavity convection remains laminar and radiative exchange controls heat transfer near peak temperatures. Increasing MPCM content yields large reductions in periodic transmittance and average heat flux (up to 50% and 40%, respectively), followed by pronounced attenuation of indoor temperature oscillations and thermal-wave delays exceeding 9 h. A maximum reduction of 2 °C in peak indoor wall surface temperature is observed under severe conditions. Melt-fraction fields reveal that phase change occurs primarily in the external wall region, while interior layers contribute minimally to latent-energy cycling. This indicates that uniform MPCM distribution is suboptimal and that concentrating MPCM in the outer part of the wall, or adopting asymmetric material grading, would further enhance thermal buffering. Results demonstrate the strong potential of MPCM-enhanced 3D-printed walls to improve dynamic thermal inertia.