Preparation Composite Phase Change Materials And Study On Building Thermal Insulation Performance

With the rapid development of economic,The energy demand is higher and higher,and the building energy consumption accounts for about 25-30%,which restricts the social and economic development.while in hot summer and warm winter area of summer,not only the climate is hot and humid,but also the solar radiation is intensity,so that the temperature of the peripheral protection structure increases,which not only forms a larger building air-conditioning load,but also causes a strong sense of barbecue and reducing the human comfort,Accordingly,It is very important to take effective insulation measures for reducing the quantity of heat to indoor and bake feeling to bring great discomfort to indoor living personnel.Phase change material is an special material,It has great application prospects in the utilization of solar energy peak-shifting and valley filling of electric power,recovery and utilization of industrial waste heat,civil and military fields.Appropriate technologies are adopted to combine phase change materials with building constructions can reduce building energy consumption,also can solve the problem of building heat insulation in hot summer and warm winter areas.In this paper,Composite phase change facing bricks were prepared by mixing composite phase change and cement,then attaching to building wall outside surface.When attain its phase change temperature,the phase change materials will phase change,using phase change materials in the phase change process of phase change latent heat to increase the thermal inertia building envelope structure,it can not only reduce the incoming indoor heat and energy consumption of buildings,and also decorate building,until good thermal insulation effect have been realized.Expanded graphite has special characteristics of porous adsorption,In this paper,expanded graphite was prepared by microwave expansion method,high latent heat of phase change paraffin was selected as phase change materials.Melt adsorption method was used for preparing paraffin/expanded graphite composite phase change material.The properties of paraffin/expanded graphite composites with different contents were characterized by SEM,saturation analysis DSC,thermal stability analysis and XRD.The experimental results showed that when the paraffin content of the phase change material is 90%,SEM and saturation analysis showed that the paraffin/expanded graphite composite phase change material had the best adsorption rate,and no leakage phenomenon in the process of phase change,DSC test results show that the phase transition temperature of paraffin/expanded graphite composite phase change materials is 41.1 ℃,and the phase change latent heat is 224.7 J/g,high phase change latent heat has still maintained.compared with the pure paraffin,phase transition temperature change is not obvious.Also,after cycle 100 times,The paraffin/expanded graphite composite phase change materials still maintain good stability,XRD test results show that the paraffin and expanded graphite has good compatibility.The paraffin/expanded graphite composite phase change material was mixed with cement to prepare the composite phase change facing brick.The influence of the addition of paraffin/expanded graphite composite phase change material on cement was studied,mainly including the apparent density,heat transfer heat storage properties and mechanical properties.The results showed that with the increase of the content of paraffin/expanded graphite composite phase change materials,the composite phase change facing brick of apparent density is reducing trend,the coefficient of thermal conductivity,the heat storage coefficient,and phase change latent heat are increasing trend,compressive strength is special,The paraffin/expanded graphite composite phase change materials has weakened the face brick of compressive strength,while the content of paraffin/expanded graphite composite phase change materials was 20%,the compressive strength has a maximum value,that is 5.01 MPa.A large number of composite phase change facing bricks were prepared by using the proportion of paraffin/expanded graphite composite phase change materials with cement as the optimal matching.Ordinary ceramic tiles were added as the comparison group,which were respectively attached to the outer side surface of 800 mm x 800 mm x 800 mm cube box,solar irradiation was going for studying the temperature changes at various points on the surface of the cube box.The results show that after three consecutive days of solar radiation,under the same external conditions,the composite phase change facing brick has better than heat insulation performance than the ceramic tile,except that the temperature fluctuation of the north surface,in addition to the north side surface temperature fluctuation is not obvious,in other directions that were performed,As can be seen from the test results,The east side of inside and outside surface of maximum temperature difference of phase transformation group is-1.2℃,-2.1℃,-1.3℃,the ordinary ceramic tile is-1.1℃,-2.0℃,-0.2℃;South the highest temperature phase change of inside and outside surface is-2.5℃,-2.5℃,-2.3℃;Ordinary ceramic tile is-2.3℃,-2.2℃,-1.8℃;Highest temperature difference phase transformation of the west side of inside and outside surface is-3.5℃,-1.2℃,-2.9℃,ordinary ceramic tile is-3.4℃,-2.2℃,-2.2℃;Top side the highest temperature phase change of inside and outside surface is-4.1℃,-5.3℃,-5.2℃;-5.5℃,-5.8 and-5.5 for ordinary ceramic tile group,which shows that the phase change material used in the building envelope has a certain heat insulation effect,achieving purpose of energy saving.Using EnergyPlus building energy simulation software,Take an office building in guangzhou which is hot in summer and warm in winter as an example,composite phase change facing brick and ordinary ceramic tile respectively applied exterior walls,load simulation and comfort evaluation were operated.The results show that,relative to the ordinary ceramic tile,when using composite phase change facing brick,The building cooling load was reduced by 5.91%,thermal comfort requirement attains level Ⅱ,indoor thermal environment is more comfortable.