Study On The Application Of Composite Phase Change Material Based On Expanded Graphite Coupled With Solar Energy In Building Energy Conservation

The problem of high global energy consumption has attracted much attention in recent years,with the greatest increase in energy consumption in buildings.In order to address the increasing energy consumption problem,this study investigates the use of phase change materials in buildings to reduce energy consumption.The first is to fill the building envelope with phase change materials to regulate indoor temperature fluctuations,the second is to use a double layer of phase change materials to absorb sunlight and convert it to solar heat for building heating,and finally to clarify the effects of the two together.The details of the research are as follows:(1)Based on the year-round human thermal comfort temperature range(18 ℃ to28 ℃)and the year-round optimal human thermal comfort temperature(24 ℃),a composite phase change material of lauryl alcohol/expanded graphite was prepared and the thermal conductivity and latent heat properties of the composite phase change material were tested,showing excellent performance in terms of thermal inertness.The phase change material was then placed in a building model and various characteristics of indoor temperature were investigated,including time delay,growth rate,thermal comfort and elapsed time per unit temperature.The results show that the solution reduces indoor temperature fluctuations and extends the time when the indoor temperature is within the human comfort temperature range.The approach can extend the time that the indoor temperature is in the comfort temperature zone by 461% for the warming process and 471% for the cooling process compared to insulated buildings.This method can therefore increase human comfort while reducing the length of time that air conditioning equipment is switched on.(2)If the ambient temperature is more extreme in winter and fluctuations in indoor temperature cannot cover the phase change temperature of lauric acid,then the heating demand needs to be met using phase change materials.This study therefore proposes a double-layer material based on lauric acid to solve the problems of poor thermal conductivity and poor photothermal conversion performance of lauric acid.Specifically,sodium dodecyl sulphate is used to combine carbon black and lauric acid in the upper layer to enhance the photothermal conversion.An expanded graphite was added to lauric acid in the lower layer to enhance thermal conductivity.The synthesis ratio,thermal conductivity,latent heat performance and heating rate of lauric acid/carbon black-lauric acid/expanded graphite were tested.Specifically,this study specifies a preferred ratio of 100:5:1(lauric acid:carbon black:sodium dodecyl sulphate)for the photothermal conversion material in the upper layer and a preferred ratio of 100:1.4(lauric acid:expanded graphite)for the lower layer.This study also clarified that the addition of carbon material had only a small effect on the latent heat properties of the overall material.To verify the physical properties of this bilayer material,this study tested the surface heating rate of the material and the internal material during the photothermal conversion of the material.The results show that the surface temperature rise rate of lauric acid/expanded graphite-lauric acid/carbon black is 217% of that of lauric acid and 109% of that of lauric acid/expanded graphite over a 30 minute time frame.The internal temperature rise rates for lauric acid/expanded graphite/lauric acid/carbon black were 226% of lauric acid and 136% of lauric acid/expanded graphite respectively.On the basis of completing the above;two composite phase change materials and their corresponding application methods,the coupling effect between the above two application methods was further explored.Firstly,the house model was established in the 3D modelling software,and then imported into the meshing software for meshing,and then into the simulation software.Secondly,all the physical property data of the 2 composite phase change materials were collated and the physical property data were imported into the simulation software for numerical simulation experiments.The results show that with the above scheme,the average indoor temperature can be at18 ℃ for more than 50% of the day,based on an average outdoor temperature of 0 ℃in winter.This work can be used in building heating and other ways to achieve energy saving and emission reduction.This thesis has 25 figures,14 tables and 80 references.