Numerical investigation of double layered PCM building envelope during charging cycle for energy saving

An efficient operating cycle of a building envelope containing PCM layers requires a well charging cycle. The goal of this work is to carry out a detailed study to overcome situations where the PCM double layer building envelope is not efficient. Taking into account numerous combinations of melting temperatures (0m1, 0m2), and latent heat (Ste1, Ste2), the heat lost over charging cycle is examined. The finite volume approach is used to solve numerically the mathematical model that governs the configuration. The obtained results show that the melting temperature of outer PCM layer is the main controlling parameter of the heat lost amount, where increasing 0m1 increases the heat lost, such as, combination (0m1=0.7, 0m2=0.5) releases the ratio of 18% as extra heat more than the reference case (without PCM). While, for the combination (0m1=0.5, 0m2=0.7) it achieves 13%. Moreover, it is better for the latent heat of the inner layer to be lower than the latent heat of the outer layer, which leads to a strong solidification process, then, a high amount of released heat could be achieved. As well as, for combination (Ste1=0.1, Ste2=0.01) the extra heat released ratio was 15%, while for (Ste1=0.1, Ste2=0.5) it was 8%.