Heat Transfer Analysis Of Phase Change Wall And Its Architectural Application

Phase change material(PCM)in phase change wall can store and absorb indoor and outdoor heat through latent heat energy storage.It can reduce the fluctuation of indoor temperature and the cooling and heating load required by air conditioning system,so that thermal comfort of indoor environment can be improved,and achieve the corresponding energy saving effect.In the heat transfer analysis of PCM wall,it is necessary to consider the influence of PCM natural convection on heat transfer.When PCM wall is applied in buildings,it is necessary to consider the influence of PCM on the annual room temperature energy consumption of buildings.In depth study of the above issues are conducive to promote the application of PCM in building walls,and these are of great significance to building energy conservation.In this paper,the model of PCM wall is established,and the parameters of average melting rate,average solidification rate and phase change rate difference are defined.The phase change rates of convection thermal conductivity model and pure thermal conductivity model are compared.The change rules of phase change rate,indoor temperature of wall and heat passing through wall are studied when the thermal physical parameters and wall structure parameters change,and the results suitable for summer are obtained.On this basis,the double-layer phase change wall building is established.Compared with ordinary buildings,the annual temperature control effect and energy saving potential of double-layer phase change wall in different cities are obtained.The results show that:(1)The effect of natural convection on the melting process of PCM is greater than that of solidification process.Natural convection is dominant in the melting process,and heat conduction is dominant in the solidification process.By defining and comparing the phase change rate difference,it is found that the influence of natural convection on the phase change process is positively correlated with the thermal conductivity,and negatively correlated with the phase change temperature and the thickness of the phase change layer.(2)The temperature decay and the heat passing through the wall decrease with the increase of latent heat,thickness of phase change layer and the distance between PCM and external wall.When the phase change temperature is closer to the average temperature of the environment,the temperature decay and the heat passing through the wall are smaller,but the change of thermal conductivity has little effect on them.When the parameters(except the thermal conductivity)change,the heat change is between 20.32% and 40.75%.Among them,the position of PCM has the greatest influence on the heat,and the phase change temperature has the greatest influence on the heat among the thermophysical parameters,which indicates that the phase change temperature of materials should be given priority in the selection of PCM.By fitting the temperature decay curve,the optimal values of latent heat of phase change and thickness of phase change layer on indoor temperature regulation are 330 kg / k J and 8 cm,respectively.(3)The energy-saving rate of double-layer phase change wall for each city is 5.45% ～20.14%,and the energy-saving effect is considerable.PCM combined with air conditioning system can achieve dehumidification effect and make the indoor thermal comfort level I,and the dehumidification effect is between 1.381% and 6.437%.(4)Through three angles(room temperature,energy consumption,thermal comfort),using temperature difference,temperature attenuation factor,energy saving rate,PMV and PPD index,this paper quantitatively studies the application effect of double-layer phase change wall in different cities: the application effect in Harbin and Beijing in winter is greater than that in other seasons;The application effect in winter in Wuhan is less than that in other seasons;The application effect in summer in Guangzhou is less than that in other seasons;There is little difference in the application effect in Kunming.