Structural Optimization And Characteristic Analysis Of Solar Phase Change Heat Storage Tank

Phase change heat storage technology is regarded as the storage with the most development potential because the phase change material used in it can store or release a large amount of heat energy when it reforms its phase structure during the melting and solidification process,and the temperature change during operation is small or even unchanged.With an efficient and clean phase-change thermal storage energy system,it can minimize the system’s dependence on secondary energy or carbon-based fuels,thereby improving the reliability of heat from renewable energy,and by Use during non-sunshine periods to eliminate supply fluctuations.Therefore,it is meaningful to optimize the structure of the solar phase change heat storage tank and analyze the heat storage and release characteristics.This article first introduces the domestic and foreign development status of phase change heat storage enhanced heat transfer technology from three aspects:increasing heat transfer area,improving thermal conductivity,and increasing heat transfer temperature difference.In particular,increasing heat transfer temperature difference is more convenient in practical application.And the effect is remarkable.Then establish a mathematical model to describe the conservation equations of energy,mass and momentum used in the heat transfer process.The calculation formula of the liquid phase ratio is given,the purpose is to describe the heat storage or release rate of the phase change material in the heat storage unit.On the basis of using Gambit software to optimize the structure of the heat storage unit in the heat storage tank,the heat storage process and heat release process of the heat storage unit are simulated,and conclusions are drawn:（1）In the heat storage process,by adding fins of different lengths,different numbers,and different arrangements,the corrugated tube heat storage unit is optimized and the final structural optimization plan is determined,that is,4 sets of fins are added to the heat storage unit,The length is 4mm,theθis 45°and the length of the fin is increased to5mm near the exit.The heat storage process of the heat storage unit in this scheme is simulated.Compared with the corrugated tube phase change heat storage unit without fins,the time for the PCM in the heat storage unit to completely transform from the solid phase to the liquid phase is greatly shortened.In the heat storage process,as the HTF inlet flow rate increases and the initial temperature of the heat storage unit increases,the time required for the PCM in the heat storage unit to completely melt gradually decreases.During the heat release process,as the inlet flow rate of the HTF decreases and the inlet temperature increases,the average outlet temperature gradually increases.（2）Under the working conditions of this article,the cascade phase change heat storage unit adopts RT85-RT80-RT75 combination,when the phase change latent heat PCM-1<PCM-2<PCM-3 and V_PCM-1:V_PCM-2:V_PCM-3=3:2:1,the heat storage performance is the best.Not only that,the increase in the latent heat value of PCM-2 and PCM-3 will also lead to an increase in the overall heat storage capacity of the heat storage unit.This solution has good heat storage performance.At the same time,it also explores the influence of fluid flow velocity and fluid temperature in the pipeline on the heat storage performance during the heat storage process.The study shows that as the flow rate of the hot fluid increases,the fluid temperature rises,and the cascade phase change heat storage The time for the overall liquid phase ratio of the unit heat storage unit to reach 1 is getting shorter and shorter,but the degree of change in the complete melting time of the phase change material in the heat storage unit is getting smaller and smaller.In the heat release process of the thermal storage unit,the flow rate of the thermal fluid is opposite to that of the thermal fluid during the thermal storage process,and the heat release performance is the best.