Optimal location of PCM layer in building walls under Nanjing (China) weather conditions

The phase change material (PCM) location in the building walls has great effects on the thermal performance improvement of PCM walls. In this paper, a numerical model was built to estimate the optimal PCM locations in the wall during different seasons under Nanjing (China) weather conditions. The heat flux fluctuation reduction rate was used to evaluate the effects of the PCM on the thermal performance of the wall; the optimal PCM location meant the heat flux fluctuation reduction rate was the largest. The heat of fusion of the PCM used in the model was 179 J g(-1); it was found that when the phase change temperature range of PCM was 26-28 A degrees C, the optimal PCM locations in Nanjing for spring, summer, autumn, winter and a whole year were 8/16, 2/16, 5/16, 8/16 and 4/16 L, respectively. However, the PCM had great effects only in summer because of its high phase change temperature. It was also found that the optimal phase change temperature ranges for spring, summer, autumn, winter and a whole year were 24-26, 26-28, 24-26, 20-22 and 24-26 A degrees C. Accordingly, the optimal PCM locations were 0/16, 2/16, 1/16, 3/16 and 0/16 L. In addition, the most suitable kind of PCM for a certain location in the wall could also be found.