Research On The Preparation And Thermophysical Properties Of Coated Composite Phase Change Heat Storage Materials

In recent years,in order to promote the transformation of the primary energy consumption structure,reduce the abandoned wind and light power,and improve the utilization rate of new energy power generation,heat storage technology has received extensive research and attention.One of the main technical routes of heat storage technology is to store excess new energy generation in the form of heat energy through regenerative electric boilers and release it at peak heat load,breaking through the space-time limit of energy utilization and expanding the absorption space of new energy generation.The core of regenerative electric boiler is heat storage material,so the development of a kind of heat storage material with better structural performance and heat storage performance has become a research hotspot in recent years.In this paper,NaCl-KCl/SiC composite phase change heat storage materials were successfully prepared by mixed sintering method,using NaCl-KCl as phase change material,SiC as matrix material and aluminum dihydrogen phosphate as binder.The preparation technology and flow chart of the composite phase change heat storage materials were established by experiments.The parameters and conditions of the preparation process were determined by experimental analysis.Using XRD phase analysis for materials,using SEM observation of the microstructure of materials,materials for the TG-DSC analysis,determination of the phase change latent heat and phase transition temperature,testing the compressive strength of materials,bulk density,specific heat,coefficient of thermal conductivity,thermal diffusivity,coefficient of thermal expansion and series of structural and thermal physical property parameters;The thermal cycling stability of the material was tested by 100 heating-cooling cycles.Experimental results show that:from the appearance of sintering material and weightlessness rate analysis,phase change materials in raw material proportioning quality score should be 20?30%,the highest sintering temperature 700?,the initial phase sintering process should use smaller heating rate,makes the impurity in the body can fully volatile,can be appropriately increase the rate of temperature in high temperature stage;According to the analysis of density and compressive strength of the material,the forming pressure of the material is 20MPa and the holding pressure is 10min.XRD analysis showed that no new phase was formed in the sintering process of phase change material and matrix material,and they had good chemical compatibility.The SEM results show that a relatively complete three-dimensional microstructure has been formed in the composite phase change heat storage materials after sintering at high temperature,and the matrix skeleton and the phase change material are well combined.TG-DSC analysis shows that when the content of the original phase change material is 30%,the material has the best heat storage performance,the latent heat of phase change material reaches 78.19J/g,and the phase change temperature is 656.2?.Therefore,30%should be used as the best material ratio for the preparation of the material.When the content of the original phase change material is 30%,the thermal conductivity of the composite phase change heat storage material is 6.911W·m-1·k-1,which shows good thermal conductivity.After sintering,the compressive strength of the composite phase change heat storage material is 42.6MPa,which can meet the practical work needs.After 100 heating-cooling cycles,the weight loss rate is 4.42%,and the weight loss curve gradually becomes flat,indicating that the phase change heat storage material of NaCl-KCl/SiC composite has good thermal cycling stability.