Numerical study on the effects of PCM layout and layer configuration on envelope thermal performance: a comparative study in cold climates

The energy conservation advantages of phase change materials (PCMs) in building envelopes have been widely recognized. A modified mixed convective heat transfer coefficient model for the exterior surface of building envelopes is constructed. The heat transfer process and thermal performance of six cases with different PCM layouts and layer configurations are numerically investigated in summer and winter. The modified model is proven to be in better agreement with published experimental data than conventional classical models. Single-layer placement on the interior and exterior sides is found to be more suitable for thermal insulation in winter and summer, respectively. In summer, the envelope of the roof with dual-layer PCM improves the reduction of indoor temperature rise by 26.9% compared with the wall installation. In winter, the envelope of the walls with dual-layer PCM enhances thermal insulation performance by 23.6% compared with the roof installation. The optimal envelope thermal performance is achieved by installing dual-layer PCM on both the wall and the roof, which significantly mitigates indoor temperature rise in summer and reduces heating load by 48.1% in winter. The findings provide design guidance for the application of building envelopes incorporating dual-layer PCM in the representative climate conditions.