Thermal performance study of double-layer heterogeneous phase change wall under active and passive regulations in different seasons

Combining phase change materials (PCMs) with building envelopes has emerged as an effective means to improve the thermal performance of envelopes and achieve the energy conservation and emission reduction in buildings. However, the PCM envelopes with constant phase change temperature and thermal conductivity typically work in a single season and have limited thermal regulation functions. This study proposed a double-layer heterogeneous phase change (DHPC) wall, composing two kinds of PCMs with different thermal conductivities and phase change temperatures. The thermal storage capacity, energy-saving rate and indoor thermal comfort of DHPC wall were analyzed under passive and active regulation strategies to evaluated its thermal performance in different seasons. In summer, the peak temperature of DHPC wall/box decreased by 6.6 °C/1.5 °C compared with the gypsum wall/box, which was further lowered by 1.7 °C/3.3 °C after introducing the cool water. In winter, the average temperature drop rate of gypsum/DHPC wall was 3.7/1.6 °C/h, and the thermal comfort interval duration of DHPC box increased to 92.8% ∼ 87.7% after introducing the hot water. Compared with gypsum wall/box, the attenuation factor and heat load level of DHPC wall/box decreased by 6.7% ∼ 27.3% and 4.0% ∼ 67.6% respectively, the heat storage coefficient increased by −4.2% ∼ 197.1%, and the energy-saving rate reached 9.0% ∼ 22.7%. The results showed that DHPC wall could efficiently meet the thermal requirements in winter and summer, and thus had broad application prospects.