Heat Transfer Characteristics And Performance Optimization Of Phase Change Insulation Wall In Hot Summer And Cold Winter Area

In face of the growing problem of building energy consumption,the state continues to improve building energy conservation standards,pay attention to energy conservation and emission reduction.Phase change materials are applied to building walls as a new type of energy-saving technology.The heat absorption and heat release characteristics of phase change materials are used to change the heat conduction process of the wall and improve the indoor thermal environment of the building,so as to effectively reduce the energy consumption of the building.Taking Nanchang as an example,this paper explores the selection method of suitable phase change temperature of phase change wall in hot summer and cold winter.Furthermore,analyzing the heat transfer characteristics of phase change wall with different structures and the influence of phase change wall on the energy consumption of air conditioning operation.The details are as follows:(1)The physical model and mathematical model of the phase change wall were established.Meanwhile,the numerical simulation results were compared with the experimental results in the literature to verify the applicability and accuracy of using CFD to simulate the heat transfer process of the phase change wall.(2)Considering the influence of different orientations,structures and insulation layers on the suitable phase change temperature of the phase change wall.Based on the judgment of surface temperature,attenuation factor,delay time and latent heat utilization rate of phase change materials,the suitable phase transition temperature of different facing phase change walls is obtained.The suitable phase change temperatures of the east,south,west and north directions of the outer phase change wall are respectively 34～36°C,32～34°C,34～36°C and 32～34°C.The suitable phase transition temperatures of the inner phase change wall are respectively 28～30°C,27～29°C,28～30°C and 27～29°C.Taking the west-facing wall as an example,the influence of the insulation layer on the phase change temperature was analyzed.The calculation results show that the existence of the insulation layer has a great influence on the selection of suitable phase change temperature of different structural walls.The suitable phase transition temperature on the outside and the suitable phase transition temperature on the inner side are reduced.(3)On the basis of the optimization of phase change temperature parameters,the heat transfer characteristics of phase change walls of different structures are revealed.Furthermore,the influence of phase change latent heat,thermal conductivity and phase change layer thickness on the heat transfer characteristics of the inner phase change wall,and the influence of the insulating layer on the heat transfer characteristics of the phase change wall were studied.The maximum temperature of the inner surface of the inner phase change wall is reduced by 1.06°C,the average temperature is reduced by0.08°C,the heat storage on the inner surface is reduced by 53k J/m~2,and the average heat transfer coefficient is reduced by 0.08W/(m~2·K).(4)The energy consumption of buildings with different structures of phase change walls in summer is analyzed and compared with the control group of wall buildings without phase change materials.The results show that the summer energy consumption of the inner and outer phase change walls is respectively reduced by 2.96%and 2.08%,respectively.The effect of the inner phase change wall in reducing the building energy consumption is more significant.After adding the insulation layer,the summer energy consumption of the outer phase change wall I,the outer phase change wall II and the inner phase change wall is respectively reduced by 0.67%,1.30%and 1.00%.There are insulated exterior phase change walls II reduce building energy consumption more significantly.