Suitability Analysis And Optimization Design Of S Olar Energy Phase Change Energy Storage Wall

There are abundant solar energy resources in Western China.Developing passive solar heating buildings according to local conditions will play a positive role in solving the contradiction between heating energy and ecological protection of rural buildings in ecologically fragile areas.However,due to the instability and discontinuity of solar energy,the fluctuation of indoor air temperature in passive solar buildings is obvious,and indoor temperature often can not meet the requirements of human thermal comfort.Heat storage by envelope structure can effectively adjust the temperature difference between day and night of indoor air,which plays an important role in improving the thermal performance of passive solar buildings and thermal comfort of rooms.In this paper,the application of passive solar energy buildings combined with phase change energy storage wall is proposed.The contradiction between intermittent solar energy supply and building heating load in terms of time and demand is solved by the heat storage characteristics of phase change materials.Based on the field investigation and test of existing solar energy buildings,this paper puts forward the research idea of combining phase change energy storage wall with solar energy buildings,aiming at the problems of large fluctuation range of indoor temperature and poor thermal environment stability in rural solar energy buildings.Based on the analysis of phase change heat transfer characteristics,a phase change energy storage wall model is established and evaluated.Then the theoretical model of heat transfer for passive solar energy rural heating buildingys with phase change energy storage wall is established.From the perspective of indoor thermal comfort,considering the influence of phase change temperature,thermal conductivity,latent heat value,building model parameters and dosage of phase change materials,the application effect of phase change energy storage wall passive solar rural heating building is analyzed.Finally,the thickness of phase change material layer is designed by the principle of thermal penetration,and the thermal comfort of the optimized room is evaluated.The main results of this paper are as follows:(1)By testing the thermal environment of a residential building in Lhasa area,it is found that the solar radiation intensity is relatively high,and it contributes a lot to the indoor thermal environment.However,there is still a problem of large fluctuations in indoor air temperature at present.The idea of combining passive solar building with phase change energy storage wall is put forward.It is pointed out that for solar energy buildings with phase change energy storage walls,the improvement effect of indoor thermal comfort should be considered comprehensively from the perspective of obj ective environment and human thermal comfort demand.Finally,the application effect evaluation index of phase change energy storage walls is determined as indoor air temperature fluctuation and "Daily indoor temperature discomfort hours".(2)Based on the characteristics of passive solar rural heating buildings,a representative building model is established.Based on this model,the Fourier series method is used to express the inner surface temperature of buildings under the coupling of internal and external thermal disturbances.It can be seen from the variation of thermal disturbance of indoor side fluctuation that phase change material layer is disposed on the inner side of the wall can make the phase change material play a better role in suppressing indoor air temperature fluctuation.(3)By optimizing the thermophysical parameters of phase change materials,it can be found that when the phase change temperature is too high or too low,it is not conducive to the performance of materials.The thermal conductivity has little effect on the room temperature in the exothermic stage of the material,but more significant effect on the room temperature in the endothermic stage.In order to make the selected phase change materials used in the wall achieve better results,it is suggested that the ratio of length to width of the building be 1.4:1 under the climate conditions in Lhasa.(4)Through calculation,the thermal penetration depth of the wall in different directions is obtained:the thermal penetration depth of the south wall is 39 mm,the east wall is 35 mm,and the north wall and the west wall is 34 mm.The range of indoor temperature fluctuation before optimization is 10.9?26.5 ?,and after optimization is 14.5?24.3 ?.Through optimization,the fluctuation of indoor temperature is obviously restrained,and the indoor temperature discomfort is reduced by 63.0%.Through the study of this paper,we hope to provide useful theoretical reference for the application and optimization of phase change materials in the envelope structure.