Preparation And Characterization Of Enhancement Thermal Performance Of Phase Change Materials

Since energy and environment are of keen concern,and the problem become more and more severe nowadays,investigation on phase change materials(PCMs)is a hot subject worldwide,and it is generally accepted as one of the most effective method to find a way out.The varied types of PCMs make it easily applied under both high and low temperature.However,the low thermal conductivity strongly decrease its heat absorption and release of latent heat,and further hinder its application.Traditional reinforcement method focuses on the use of fins and heat pipes to enhance efficiency of thermal exchange.An increased interest on improving the thermal conductivity by the natural property of material is shown in recent research.In this thesis,sodium chloride and its aqueous solution,as well as silicon nitride,are employed to improve thermal conductivity and reduce supercooling degree.We propose a concept that a few particles could improve thermal density of phase change materials.And this is already certified in experiment and theory.Silicon nitride,titanium barbide,barbon nanotubes are all employed as reinforced fillers for phase change microcapsules based on poly(methyl methacrylate)shell and n-octadecane core to enhance thermal conductivity.There are “molecular bridges” connecting inorganic particles and polymer.A mesh spherical shell filling with PCMs is formed of polymer and inorganic particles by this way.This structure,on the one hand,could build thermal conductivity channel to core of microcapsules and further enhances thermal conductivity of polymer shell.On the other hand,the mechanical performance of enhancement capsules is higher than that of common capsules.DSC,TGA,thermal conductivity device,infrared thermal imaging system,high and low temperature thermal cycling test oven and other equipment are employed to study thermal performance of PCMs.The results show a high latent heat of 110.6J/g.And thermal conductivity(0.363W/m K)is enhanced by 56.8%.It demonstrates that inorganic particles could enhance thermal conductivity,and thermal stability efficiently.In addition,we also prepare phase change nanocapsules based on polypyrrole shell which is an electrical conducting polymer.It is proved that the nanocapsules have a good thermal performance.Moreover,we design a kind of octadecyl solid-solid phase change material according to the principle of polymer segment secondary relaxation.It is an effective method to expand research and application of energy storage phase change materials.