Exploratory Experimental Research On Increasing Latent Heat Of Mixed Molten Salt

Energy is the foundation of modern society and economic development,as well as an important factor in maintaining economic prosperity and stability.In order to achieve"carbon peak",china vigorously develops renewable energy,and one of the key technologies to realize the large-scale application of renewable energy is energy storage technology.Molten salt is widely used as a medium and high temperature energy storage and heat storage medium due to its excellent properties,and the latent heat storage of molten salt has great application prospects.In order to improve the latent heat storage capacity,the research attempts to increase the latent heat value of the mixed molten salt.The From the consideration of latent heat value and economy,try to prepare mixed molten salt by mixing salt and alkali.Prepare four kinds of NaCl-Na NO₃,NaCl-NaOH,NaF-NaOH binary mixed molten salt and NaF-NaOH-NaCl ternary mixed molten salt with the same cation by the muffle furnace melting method.And the molten salt nanocomposite material added with 10nm and 30-50nm Al₂O₃nanoparticles is prepared by the microwave method.The prepared mixed molten salt and molten salt nanocomposite material was subjected to simultaneous thermal analysis test to obtain its melting point,initial crystal point and latent heat value.Among the three binary mixed molten salts with the same cation,only the NaCl-Na NO₃binary mixed molten salt achieves eutectic,while the NaCl-NaOH and NaF-NaOH binary mixed molten salt does not achieve eutectic.The NaCl-NaOH(mass ratio 1:9)binary mixed molten salt has a maximum latent heat value of301.2J/g,the initial melting temperature of 204.0?,the termination melting temperature of 331.9?,and the initial crystal point of 303.9?.At the same time,the latent heat value of the three binary mixed molten salts has the same changing trend,and the latent heat value decreases with the increase of the mass ratio of the high latent heat components(NaCl,NaF).The latent heat value of the NaF component with high latent heat mixed with alkali is lower than that of NaCl,indicating that the high latent heat component does not necessarily increase the latent heat value of the mixed molten salt.In molten salt nanocomposites,the initial melting temperature under different mass fractions and different particle sizes is the same,and the termination melting temperature is not much different from the initial crystal point.Compared with the base salt,the latent heat value of the four groups of molten salt nanocomposites with10nm Al₂O₃nanoparticles decreased by 47.1%,58.7%,38.9%,and 48.8%,respectively.Compared with the base salt,the latent heat value of the four groups of molten salt nanocomposites with 30-50nm Al₂O₃nanoparticles was reduced by 40.1%,48.4%,21.7%,and 29.6%,respectively.Both have a great reduction in the latent heat value.Compared with the particle size,both of them have the smallest reduction in the latent heat value when 1.5%is added,and the melting point and initial crystal point of the base salt are little changed.Al₂O₃nanoparticles have a complex effect on the stability of the base salt's microstructure.At the same time,the small particle size has a greater impact on the base salt.In the NaF-NaOH-NaCl ternary mixed molten salt,the maximum latent heat value of the NaF-NaOH-NaCl ternary mixed molten salt is 264.58J/g(the mass ratio is 1:6:3),compared with the latent heat value of NaCl:NaOH=1:9,it is reduced by12.2%.The micro-level interaction effects of ternary salt-alkali mixing are more complicated,and the simple mixing of high latent heat components does not necessarily produce a mixed molten salt with high latent heat.