不同气候条件下相变屋顶传热性能数值分析

Walls filled with phase change materials (PCM) can effectively reduce building energy consumption and improve thermal comfort. The porous brick roof was filled with paraffin with a phase transition temperature of 25-33℃. The equivalent temperature considering radiation and air temperature was introduced. The GPU accelerated multi-relaxation-time lattice Boltzmann method (MRT-LBM) based on enthalpy method was used to analyze the effects of paraffin wax with different phase change temperatures on the thermal response characteristics of roofs in seven cities of China in August 2020. The results of paraffin with phase change temperature of 27℃ were shown that phase change of paraffin did not occur in the building roof of Shanghai, and the entering heat flux was as high as 324.3kJ/m². The liquefaction rate of paraffin in the phase change roof of Chengdu area changed by 30%. The internal surface temperature fluctuates between 25.6℃ and 27.3℃, and the temperature difference was only 1.7℃. The entering heat flux was only 50.9kJ/m². The results indicated that the change of liquid phase rate in Wuhan and Beijing was very close, the phase transition time was 50% of the whole day and the corresponding heat flux entering the room was 0.37 times of that in Shanghai. The temperature fluctuation of the inner surface of the roof wall in Kunming and Harbin reached 4.5℃ and 4.4℃, respectively, but the corresponding temperature was 28℃. The indoor temperature fluctuation of Guangzhou was 2.6 times of that in Chengdu. Beijing, Chengdu, Wuhan and Kunming were suitable for paraffin with phase transition temperature of 27℃, while Guangzhou, Shanghai and Harbin were suitable for paraffin with phase transition temperature of 29℃, 31℃ and 25℃, respectively. This work can provide the guide for the optimization design of phase change building.