| Organic phase change material(PCM)is widely used as phase change energy storage materials due to high latent heat,low supercooling,safety and non-toxicity.At present,many researches are to solve the problems of poor shape stability and low thermal conductivity by simply packaging and adding heat conducting agent.There are few researches on the scientific problems such as the packaging effect of matrix,phase change behavior and the mechanism of heat transfer process,thus there is a lack of theoretical reference in energy storage technology innovation.In view of the above problems,the performance control and influence mechanism of modified expanded vermiculite-based organic composite PCMs were studied in this paper.Hydrochloric acid and cetyltrimethylammonium bromide were used for acid treatment and intercalation modification of the expanded vermiculite.Polyethylene glycol and paraffin were used as organic phase change energy storage media,and aluminum oxide was used as the thermal conductivity agent.The preparation of organic composite phase change energy storage materials by physical impregnation.In this paper,the effects of modification treatment on expanded vermiculite encapsulation,the phase change dynamics of PCM in the pore and heat transfer enhancement mechanism were studied,and the application value of composite energy storage materials was evaluated.The main achievements of this paper are as follows:By investigating the effect of acid treatment and organic intercalation on the pore structure of expanded vermiculite,the regulation mechanism of pores was clarified.The modification technology with the optimal pore size,pore volume and porosity were obtained,and it was proved that the two modification treatments ccould improve the surface energy and organic affinity of the layer and surface of expanded vermiculite.The prepared modified expanded vermiculite with good pore structure could be used as PCM encapsulation matrix.After the research on the packaging effect of modified expanded vermiculite organic PCM,the improvement mechanism of packaging effect was analyzed.The results showed that the encapsulation efficiency of acid-modified expanded vermiculite for organic PCM was higher than that of expanded vermiculite,and the good affinity with organic PCM was also conducive to the package of organic PCM.Under the synergistic effect,the encapsulation ratio was higher(>70 wt.%),thereby enhancing the heat storage capacity of the composite phase change energy storage material(>130 J/g).The effect of modified expanded vermiculite on the phase change behavior of PCM was explored,and the influence mechanism of phase change behavior was clarified.The study of non-isothermal crystallization kinetics showed that the modified expanded vermiculite could further reduce the nucleation activation energy of polyethylene glycol,but it still had a certain limiting effect on the polyethylene glycol crystal growth process.The intercalation treatment enhanced the affinity of the encapsulation matrix with paraffin,promoted the solidification process of paraffin,and improved the latent heat of solidification.The other application capicities of the novel modified expanded vermiculite-based organic composite phase change energy storage were evaluated by using XRD,TGA,thermal conductivity and DSC test.The results showed that the prepared composite phase change energy storage materials had excellent chemical compatibility,thermal stability,thermal conductivity and cycle reliability,and had good application potential.In this paper,a novel preparation technology of organic composite phase change energy storage materials with high shape stability,high heat storage capacity and high thermal conductivity was obtained.The theoretical research on the influence mechanism of modified matrix on PCM packaging and phase change behavior provided a theoretical reference for the preparation of high-performance pore mineral based organic composite phase change energy storage materials. |
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