Simulation Study On Performance Optimization Of Horizontal Latent Thermal Energy Storage Heat Exchangers With Movable Inner Tube

As one of the important components of shell and tube latent thermal energy storage heat exchangers,the position of the inner tube directly affects the charging/discharging performance of the heat storage.Horizontal shell and tube latent thermal energy storage heat exchangers with eccentric inner tubes can significantly improve the charging performance of traditional horizontal shell and tube latent thermal energy storage heat exchangers,but make the discharging performance worse.Therefore,this thesis proposes a horizontal shell and tube latent thermal energy storage heat exchangers with movable inner tube,which is referred to simply as MTHX,to achieve the goal of simultaneously improving the charging/discharging performance,and the influence of the inner-tube movement mode on the charging/discharging performance was studied,which has the great theoretical significance and engineering application value.The two-dimensional simulation model of MTHX is established,ICEM is used to complete meshing,user defined functions are applied to control inner tube movement,and Fluent is employed in simulating the charging/discharging process of the MTHX.And the charging and discharging processes and performance of the MTHX are studied when the inner tube moves at different speeds in different directions and ranges,the variable working condition analysis is completed,and a better inner tube movement scheme is proposed for the heat exchangers.The main conclusions are as follows,A comparative study of charging/discharging performance between MTHX and traditional shell and tube heat reservoir is carried out,and the results show that,when the inner tube moves round and forth from the center of the inner tube at a vertical downward direction,under the same mass of phase change material and initial conditio-ns of charging/discharging,compared with the traditional horizontal shell and tube latent thermal energy storage heat exchangers,the charging/discharging performance of the MTHX is improved at the same time.The charging/discharging time is shortened by 44.31%and 7.20%,and the average charging/discharging rate is increased by 81.67%and 8.80%,respectively.The effects of the inner pipe movement direction,speed and range on the charging/discharging performance of the MTHX are studied when the inner tube moves at different speeds in different directions and ranges.The results show that,the charging performance of the MTHX with the inner tube moving vertically and backward in the vertical downward direction of the horizontal plane is better,and the discharging performance of the MTHX with the inner pipe moving vertically and upward along the horizontal plane is better.The influence of the inner tube movement range on the charging performance of the MTHX depends on the direction of inner tube movement,the influence of the inner tube movement range on the discharging performance of the MTHX is not affected by the direction of movement,and when the movement range of the inner tube is set to 10 mm,the discharging performance is better.Increasing the movement rate of the inner tube can improve the charging/discharging performance,but the effect on the discharging performance is more significant.Taking the MTHX with the inner pipe moving vertically and downward in the horizontal plane as an example,when the inner pipe movement rate is increased from 0.1 mm/s to 0.5 mm/s,the average charging rate of the heat reservoir is increased by 12.60%,and the discharging rate is increased by 40.33%.Finally,based on the results of the influence of inner tube movement direction,speed and range on the charging/discharging performance of the horizontal shell and tube latent thermal energy storage heat exchangers with movable inner tube,six inner tube movement schemes are proposed,and the charging/discharging performances of the heat exchangers with different inner tube movement schemes are studied.The results show that,compared with the traditional heat exchangers,the charging/discharging time of the inner tube movable shell and tube phase change heat storage with the best inner tube movement scheme is shortened by 78.88%and 57.65%,the total time is shortened by 64.97%,and the average charging/discharging rate is increased by 348.71%and 115.11%,respectively,which suggests a significant improvement in charging/discharging performance.In this thesis,the influence of the movement direction,rate and range of inner tube on the charging/discharging performance of the MTHX is studied,and the optimal inner tube movement scheme of the MTHX is obtained,which can lay a foundation for the engineering application of the MTHX.