Heat And Moisture Transfer Characteristics Of Phase Change Wall In Hot Summer And Cold Winter Region

Phase change materials are used in building walls to improve the thermal inertia of building walls,reduce the peak indoor temperature through two-way transmission,improve human comfort,and achieve the purpose of building energy conservation.In normal walls,heat and moisture are transferred by conduction and diffusion,while in phase change walls,the presence of phase change materials affects the heat and moisture transfer process within the wall,so it is more complicated.In addition,as the single-layer PCM wall has poor year-round applicability in areas with hot summer and cold winter,the PCM wall in this paper is equipped with high-temperature PCM and low-temperature PCM on both sides of the main brick layer respectively,so as to adapt to the characteristics of areas with hot summer and cold winter and play the advantages of PCM energy storage in winter and summer.Based on this,based on the review of the research on heat and moisture transfer of PCM wall at home and abroad,the optimal incorporation ratio of PCM material was obtained by preparing test blocks to test its performance,and corresponding PCM wall and ordinary wall were built for test.The research contents of this paper are as follows:(1)Summarize the research status of heat and moisture transfer of PCM wall in recent years from the aspects of theoretical model development of wall heat and moisture transfer,research on PCM building materials,experimental research on PCM wall and numerical simulation methods.Then the basic theory of heat and moisture transfer of phase change wall is described,which mainly includes heat transfer process,moisture transfer process and phase change process.(2)According to the application principle of PCM in the wall,the PCM was selected.The optimal incorporation ratio of PCM was obtained by preparing test blocks to test their strength properties.The heat and moisture transfer performance of PCM under different mixing amounts of cement mortar based materials was analyzed.It is pointed out that the incorporation of PCM interferes with the change of moisture content in cement mortar structure and then affects the wet transfer process of building materials.(3)In the paper,through experiments in hot summer and cold winter area(Hengyang)outdoor natural environment to build a multi-layer phase change wall experiment room and ordinary wall experiment room without phase change materials.The main brick layer of the wall is aerated concrete block,phase change material with different phase change temperature is placed on both sides of the main brick layer of the phase change wall,and ordinary cement mortar with the same thickness is placed on both sides of the main brick layer of the ordinary wall.In this experiment,the temperature and humidity data of the inner and outer surfaces of the wall were collected to compare and analyze the temperature and humidity changes of the two types of wall in summer and winter,so as to study the heat and humidity transfer performance of the phase change wall in hot summer and cold winter region in winter and winter.The results show that the PCM wall can reduce the indoor temperature fluctuation and effectively reduce the indoor maximum temperature in summer,and can reduce the indoor temperature fluctuation and increase the indoor minimum temperature in winter,and the PCM wall has a certain humidity control effect in both winter and summer.(4)COMSOL Multiphysics software is used to solve and calculate the heat and humidity physical field under four conditions: phase change wall considering only heat transfer,phase change wall considering heat and humidity transfer,ordinary wall considering only heat transfer and ordinary wall considering heat and humidity transfer.The curves of wall temperature and humidity changing with time under the synergistic action of various fields are obtained to further verify the characteristics of heat and humidity transfer of phase change wall.