Seasonal adaptability analysis and thermal performance optimization of breathable and heterogeneous phase change material (B&H-PCM) walls

Phase change materials and ventilation significantly enhanced thermal performance of walls, while different parameter combinations exhibited varying effects, particularly for heterogeneous phase change materials across different seasons. This study aimed to identify the optimal parameter combination of composite phase change materials (CPCMs) for breathable and heterogeneous phase change material (B&H-PCM) walls to improve seasonal adaptability in winter and summer. A numerical model of B&H-PCM wall was established, examining the effects of phase change temperature, latent heat, thermal conductivity and thickness of double-layer CPCMs, and the optimization was performed using the Taguchi method. To comprehensively assess the energy-saving potential and thermal comfort level of B&H-PCM wall, a measure of key response (MKR) was introduced. The optimal parameter combination for CPCMs across different seasons were determined as: for paraffin wax/porous silica in the exterior layer, the phase change temperature, latent heat, thermal conductivity and thickness were 30∼36 °C, 150 kJ/kg, 0.1 W/(m·K) and 33 mm respectively, and for paraffin wax/expanded graphite in the interior layer, the corresponding values were 22∼26 °C, 200 kJ/kg, 2.2 W/(m·K) and 43 mm respectively. Following optimization, the thermal performance of B&H-PCM wall improved significantly, with MKR values increasing by 59.3 % in summer and 138.2 % in winter.