Research On Thermal Energy Storage And Release Characteristics Of Foam Aluminum Paraffin Composite Phase Change Materials

An effective method of reducing energy consumption for heating a building is to incorporate phase change material(PCM)in building wall.Research on the way to improve the property of PCM,as well as thermal properties of PCM heat storage building does help to ensure the comfort of people and use energy reasonably and effectively,and the important problems in the field of building energy are reducing building energy consumption to the minimum.In this paper,choosing paraffin phase change material as heat storage material of building wall,and the phase change temperatures,phase change latent heats and stability of paraffin mixtures with different mass ratio by mix up low melting liquid paraffin with high melting solid paraffin were studied experimentally by differential scanning calorimeter(DSC).It shows that,the mixed paraffin wax with latent heat of phase change between 60~70 J/g and phase transition temperature between 19~29?was selected,as an ideal phase change material in wall when the ratio of 7: 13,3: 7 is reached.Measuring thermal conductivity of paraffin mixed phase-change material using KD2 Pro thermal analyzer,it shows that thermal conductivity of mixed phase change materials is low,and with the increase of liquid wax content decreased.of paraffin phase-change material,with aluminum foam as porous matrix,melting point close to the optimal temperature of mixed paraffin,preparation of aluminum foam /paraffin composite phase-change material,and put it into the wall.Using fusion method obtain the shape-stabilized phase change material,which include high density polyethylene(HDPE)and paraffin mixtures,in order to solve the leakage problems during the melting of phase-change material.The microstructure and the surrounding of the samples are observed by 3D laser microscope,the optimum phase-change material with the best ratio of 1:4 is more average,close,and better accommodates paraffin.The phase change temperatures,phase change latent heats,uniformity stability and thermal conductivity of shape-stabilized phase change materialwere studied experimentally by differential scanning calorimeter(DSC)and KD2 Pro thermal analyzer.It shows that the addition of polyethylene has little effect on the phase change temperatures,phase change latent heats and thermal conductivity,and the stability and uniformity of the shape-stabilized phase change material are better.However shape-stabilized phase change material as a heat storage material in the wall there is a small thermal conductivity,flammable shortcomings.In order to improve the thermal performance of paraffin phase-change material,with aluminum foam as porous matrix,melting point close to the optimal temperature of mixed paraffin,preparation of aluminum foam / paraffin composite phase-change material(English,referred to as FAPC phase change material),and the thermal conductivity and phase change latent heats were studied experimentally.The results show that,the phase change latent heat of the composite phase change material with foam aluminum only decreased by 2%,but its thermal conductivity was improved greatly.and it is improved by nearly 10 times than that of polyethylene / paraffin,so the heat transfer effect is remarkable.The foam aluminum/paraffin composite phase change material is placed in the wall structure,the experimental study was used to reach on thermal energy storage and release characteristics of composite phase change wall,and the effect of phase change walls on the channel and the room,to test the practicality of composite phase change materials.The results show that,if the composite phase change material is placed in the wall structure,the temperature range of the room is smaller,the phenomenon of temperature delay is obvious,has effect on the temperature distribution of solar panels too.A full size two-dimensional heat transfer model is abstracted,and the FLUENT software is adopted to carry out numerical simulation for the temperature distribution of the building envelope blending with mixed phase change materials and composite phase change material.The results show that,if phase change materials are applied in the south wall,and the melting point close to the appropriate temperature,it can keep the temperature stability in a long time.During the time of energy storage,the melting rate of aluminum / paraffin composite phase change wall is much greater than that of paraffin mixed phase change wall,and the temperature gradually rising along the height direction in the Trombe wall structure.During the time of energy release,the liquefaction rate of the mixed phase change materials is higher than that of the other two groups.And the smaller the thermal conductivity,the more obvious the roomtemperature drop,to improve the thermal conductivity of materials is good to wall insulation.Through the experimental research and numerical simulation,it shows that,if the composite phase change material is placed in the wall,the initial and the phase stage of melting are basically.Since the time of the phase transition process in the simulation is longer than the experimental,and we can not be completely insulated when the experimental research,so the results of experimental and the simulation have a certain deviation,the experimental value is low,but the maximum is not more than 18%,it meet the actual requirements in a certain range of error.So adding of copper foam can significantly increase the coefficient of thermal conductivity of composite materials,achieving the goal of building energy efficiency.