Research On Preparation And Rrelated Properties Of Fly Ash Composite Phase Change Material

Phase change energy storage material(PCM)is a kind of material which can store heat energy and control temperature by endothermic or exothermic effect during phase change.It is widely used in construction industries,military fields,clothing and electronics and other fields.In order to realize the sustainable development of energy conservation and emission reduction,improve the utilization rate of phase change materials and reduce the cost,further research on phase change energy storage materials has important industrial significance and scientific significance.Fatty acid phase change materials,such as myristic acid(MA),lauric acid(LA)and stearic acid(SA),have lower melting point,higher enthalpy value of phase change,energy storage density and heat storage capacity,and their phase change process has a series of good physical and chemical properties,which are rich in resources and economical and practical in the market.However,the simple fatty acid transformation temperature is high,the thermal conductivity is low and easy to leak,so it is not suitable for the application of low-temperature phase change energy storage system,so it can not be used as a phase change material alone.Fly ash is a kind of high quality active admixture,which has the advantages of good stability,high impermeability and good thermal cycling in the process of use.Therefore,the mixture of lauric acid/stearic acid and myristic acid/stearic acid with a certain mass fraction prepared by fly ash as the material substrate can be used as composite heat storage materials,which can effectively improve the energy utilization rate.In this paper,a kind of composite phase change heat storage material(PCM)based on fly ash is developed.The material takes fly ash as the matrix,adds a certain mass fraction of lauric acid/stearic acid,myristic acid/stearic acid mixture,and combines with a certain pressing process to finally produce fly ash based phase change heat storage material.Physical adsorption,X-ray diffraction,Fourier transform infrared spectroscopy and microstructure characterization of the prepared fly ash composite phase change material were carried out,and the mechanical properties and heat storage properties of the fly ash composite phase change material were tested and analyzed,and the following conclusions were drawn:(1)The phase structure of fly ash composite phase change material was characterized and analyzed.By X-ray diffraction pattern,it is found that the phase change material of MA-SA/LA-SA mixture does not change the original crystal phase structure of fly ash when it is embedded into the pores or adsorbed on the surface of fly ash.Fourier transform infrared spectrum analysis shows that the MA-SA/LA-SA mixture can penetrate into the internal crack structure of fly ash and exist independently.No relevant chemical reactions occurred and no new substances were generated.The scanning electron microscope and transmission electron microscope analysis showed that MA-SA and LA-SA phase change materials could wrap fly ash and embed into the holes of fly ash.(2)To explore the influence of PCM content on the mechanical properties of fly ash composite phase change materials.The addition of PCM mixture can improve the drying shrinkage deformation of fly ash material and improve the drying shrinkage performance of fly ash composite phase change material.The bending strength and Vickers hardness of the fly ash composite PCM increase,and the addition of PCM can enhance the rigidity of the fly ash composite PCM,and the fly ash composite PCM is not easy to deformation after the addition of PCM.(3)The mathematical model of thermal conductivity of fly ash composite phase change energy storage materials with different mass fraction of PCM content is established.As the mass fraction of PCM increases,the thermal conductivity gradually increases.After adding MA-SA composite or LA-SA composite to fly ash,the specific heat capacity of the fly ash composite phase change material is significantly higher than that of pure fly ash,and the specific heat value remains relatively stable at 40 ?.As the number of storage/release cycles increases,the enthalpy of phase change decreases.Within 100 cycles,the enthalpy of phase change is not obviously attenuated.When the number of cycles is between 100 and 800,the enthalpy of phase change of fly ash composite energy storage material decreases slowly.It shows that the fly ash composite energy storage material can play a stable heat storage performance in the process of heat storage/release within 800 times.There are 31 figures,20 tables and 60 references in this paper.