The Optimum Phase Transition Temperature for Building Roof with Outer Layer PCM in Different Climate Regions of China

Abstract

Outer-layer shape-stabilized phase change roof is a building roof construction that laying shape-stabilized phase change material (PCM) on the surface of the roof. The peak temperature and the decrement factor of the roof inner surface can be greatly reduced. In this study, the thermal insulation properties of this structure in five climate regions of China are studied using CFD numerical simulation. By comparing with roof without PCM, the optimal phase transition temperature for each climate region is analyzed. The results show that the phase transition temperature of the PCM in the roof increases linearly with the increase of the average outdoor solar air temperature. The optimum phase transition temperatures in severe cold region, cold region, hot summer and cold winter region, hot summer and warm winter region, and mild region are 31~33°C, 34~36°C,36~38°C, 34~36°C, and 29~31°C, respectively. The corresponding decrement factors of the inner surface of the roof under the optimum phase transition temperature are 0.033, 0.030, 0.033, 0.028 and 0.026, respectively. Compared with roof without PCM layer, the decrement factors are decreased by 85.90%, 87.12%, 85.78%, 87.83%, and 88.79%, and the peak temperatures of inner surface are decreased by 3.7, 4.0, 3.9, 3.8, and 3.7°C, respectively.