Performance Analysis Of Composite Phase Change Heat Storage Composite Material Of Sodium Heptahydrate/Sodium Sulfate

The application of renewable clean energy is the current trend of social development,and it is an important way to reduce environmental pollution.In clean and renewable energy,solar energy has the advantages of wide coverage,easy to obtain,and continuously provide energy to the earth in the form of direct and indirect.It also does not generate waste residue,waste water,waste gas,noise and other additives.Due to the alternation of day and night and seasonal change,the solar energy is unstable and discontinuous.Therefore,in order to provide continuous and stable solar energy,it is necessary to develop heat storage materials with large heat storage density,stable performance and cheap and easy to obtain.In this study,Mg SO4·7H2O and Na2SO4·10H2O were used as the research objects,and the composite heat storage materials with different proportions were prepared by common melting compound,and their properties were tested.In order to obtain the phase change heat storage material with phase transition temperature is about 60?,no phase separation,low degree of under cooling,large latent heat of transformation,good cycle stability.Through the phase separation condition observation,exothermic platform-degree of under cooling and phase transition temperature test,cyclic stability test,as well as TG-DTA test and phase change the amount of exothermic heat test,obtained the following results: when the mass ratio of Mg SO4·7H2O-Na2SO4·10H2O composite phase change thermal storage material is9.35:0.65 the thermal storage performance of the material is optimal;the phase transition temperature is about 64?,the length of the exothermic plateau is about 7min,no overcooling and good thermal stability,after 360 heating-cooling cycles the release of thermal energy was kept at 67.02%;the corrosion degree of the composite material to common metal materials such as copper and aluminum is low,the annual corrosion depth is about 0.003 mm and0.012mm;when the corrosion time of stainless steel is less than 180 h,the annual corrosion depth is about 0.1mm,the annual corrosion depth is more than 180 h is about 0.04 mm.