Analysis Of Heat Storage And Release Characteristics Of Molten Salt In Low Power Energy Storage Electric Furnace

Phase change energy storage technology is due to its high energy storage density.low cost.The advantages of stable and easy control of heat storage/dissipation process can effectively solve the problem of energy waste caused by"abandoned water"in hydropower stations.Phase change material energy storage technology is used to store the rich water of hydropower in the form of heat.Its thermal energy can be used twice.At the same time,it plays a certain role in the regulation of hydropower energy and improves the safety of the power grid.However,due to the low thermal conductivity of the phase change material.It hinders the heat transfer performance of the regenerator,so it restricts its large-scale application in the field of energy storage.At present,there are many scholars at home and abroad who focus on the research of heat storage systems mostly on phase change materials and convection heat transfer.There are still great difficulties in studying the heat transfer process and mechanism of the phase transition problem in complex systems.To this end,this paper discusses the selection of phase change heat storage devices and phase change materials,and uses the method of numerical simulation to study the heat storage and release process of phase change materials in low power energy storage electric furnace.details as follows:First,this paper compares different phase change heat storage materials.Finally,KNO₃-NaNO₃-LiNO₃-Ca（NO₃）₂·4H2O quaternary mixed nitrate was selected as the heat storage medium.The CFD numerical simulation method was used to study the heat transfer characteristics of the heat storage unit with or without natural convection.The effect of different heating power on the heat storage process and the phase change process in the heat storage unit under different heating methods were studied.The results show that natural convection has a greater influence on the temperature distribution and liquid phase ratio distribution of the phase transition process.In the absence of natural convection,the heat transfer characteristics are mainly heat conduction,and the melting time of the molten salt is longer;the increase in heating power can promote the natural convection of the liquid phase change material and reduce the time used for melting.When the heat flux density increases by 5000W/m2,the melting time of the phase change material decreases by 2646s,1650s,and 1111s,respectively;different heating methods will result in different shapes and flow fields of the melting area in the heat storage unit.When the bottom heating method is adopted,the flow field is more turbulent.When the side wall heating method is adopted,the flow field is moreSecondly,in order to compare the effects of material physical parameters on the entire heat storage system,the effects of phase change material density,thermal conductivity,specific heat capacity,and latent heat on the heat storage process were studied.The results show that density has a greater effect on liquid phase change materials.Reducing the density can accelerate the natural convection of liquid phase change materials and shorten the melting time.When the density increases sequentially by 25%,the melting time increases by 30.7%,25.7%,and 14.3%,respectively.The increase in thermal conductivity will shorten the melting time and make the temperature distribution in the heat storage unit more uniform.The increase of specific heat capacity and latent heat can increase the energy storage density of the heat storage unit.Thirdly,the numerical calculation method was used to study the heat transfer enhancement scheme of the energy storage electric furnace structure.Including increasing the height,number and thickness of ribs.The results show that the height of the fins has a greater influence on the melting and solidification process of the heat storage unit.The increase of fin height will change the temperature distribution and flow field distribution of the phase change material.Adding a certain number and a certain thickness of fins can enhance the heat transfer enhancement effect of the heat storage unit and shorten the melting time of the phase change material.However,the continued increase will inhibit the natural convection of the phase change material,and the melting time becomes longer.Finally,for this heat storage device,five different types of bionic fins were designed.They are rectangular,T-shaped,dendritic,polylined,and mixed.The heat storage and release process of its three-dimensional model is numerically studied.The results show that the melting front of T-type and dendritic heat storage units is wider and the temperature distribution and flow field distribution are more uniform.The relevant conclusions obtained in this paper can lay a foundation for the design,optimization and engineering application of low-power phase change materials energy storage electric furnaces.