Thermal Storage Performance Of Glycerol Stearate/Metal Foam Phase Change Materials And Modification

With the further development and research of energy storage technology,composite phase change thermal storage materials have been gaining extensive attention in the field of thermal heat storage technology because of its better comprehensive performance in storing heat.As porous skeleton material,metal foam has rich pore volume and good sizing ability,and can greatly enhance the thermal conductivity of thermal storage material.In this paper,foam metal/glyceride phase change composites were prepared with the method of melt-impregnation,using two kinds of glyceride（GMS and GTS）as phase change materials and copper and nickel foam as support material.This research was carried emphatically on microscopic mechanism,as well as heat storage performance,adsorption properties,thermal conductivity,etc.to solve the drawbacks of glyceride as a phase change material,such as low thermal conductivity and high leakage.In this paper,the relationship between the foam copper（nickel）porosity-thermal conductivity-filling ratio was studied through the calculation of metal foam porosity and the filling ratio and the analysis of thermal conductivity theory.The melt-impregnation experiment was operated at eighty degrees Celsius under vacuum condition and the adsorption tends to be saturated after one and half an hour of adsorbing.When in saturated adsorption,the greater the porosity of foam metal is,the greater the filling ratio is.On the contrary,the smaller the porosity is,the greater the proportion of metal skeleton and coefficient of thermal conductivity will be.Theoretically,the thermal conductivity can be raised from 0.19 W·m^-1·K^-1 of glyceride to 4-8 W·m^-1·K^-1 of nickel foam/glyceride and 9-15 W·m^-1·K^-11 of bubble copper/glyceride.Specific surface area is an important indicator of microporous material adsorption performance.It has been demonstrated in a cycle experiment that the leakage of metal foam/glyceride is between 15%and 50%after one hundred times of cycles.Metal foam/glyceride heat storage material modified by nanometer graphite pieces was prepared by surface modification experiments using ultrasonic stripping preparation of nano flake graphite（GnPs）.In this paper,the author focused on several questions through some research methods like differential scanning thermal analysis,characteristics analysis of surface topography,XRD,thermal conductivity test and thermal cycling test experiment.The microstructure and thermal storage performance of the material was studied with these methods.And the author also discussed the enhancement mechanism of materials with the modification of nano graphite flake to thermal conductivity and adsorption performance.Nanoscale fold structure over the surface of metal skeleton was observed in SEM text.This kind of structure formed network in the pore by crosslinking,which increased heat transfer efficiency and thus improved the thermal conductivity.The thermal conductivity had a 10%-20%raise from 11.1-13.6 W·m^-1·K^-1 to 13.7-16.4 W·m^-1·K^-1measure by the laser flash method.DSC test has shown that the phase change temperature interval of GMS/foam metal composite was 54.0-61.3℃,the phase transition temperature of it was 60.0℃and the latent heat of it was 54.1-85.4 J/g.The phase change latent heat slightly decreased after adding GnPs.A series of glyceride/DMDBS Gel composite materials were prepared using1,3:2,4-di-（3,4-dimethyl）benzylidene sorbitol（DMDBS）as gelator and glyceride as PCM.And the foam metal/glyceride Gel material was prepared using foam metal as the skeleton.The heat storage performance of Gel materials and the microcosmic mechanism was studied with analysis methods such as SEM,XRD,DSC,UV and FI-IR and the thermal performance test.When adding 3 wt%DMDBS in glyceride,the Gel-sol transition temperature of composite phase change materials was 159℃and the leakage was only 6%.The melting heat and freezing heat of 3%GTS/DMDBS composite phase change materials was 126.4 and 105J·g^-1 respectively.Through UV absorption spectrum and IR absorption spectrum,the driving force of the three-dimensional network structure,which formed in the self-assembly of DMDBS in GTS,was the accumulation of and hydrogen bonding.