Analysis Of The Flow Dead Zone And Flow Pattern Characteristics In The Shell Side Of The Torsional Flow Heat Exchanger

Based on the background of "saving energy and protecting the environment" in our country,scholars have conducted various discussions and researches on the problem of "how to improve the heat transfer performance of the hot and cold fluid in the heat exchanger".Based on the flow and heat transfer of the high-efficiency torsional flow shell-and-tube heat exchanger,this paper conducts a qualitative and quantitative analysis of the flow dead zone in the torsional flow heat exchanger through a combination of theoretical analysis and numerical simulation.The internal connection between the dead zone of flow and heat transfer performance is further elaborated,and the flow pattern of the fully developed section of the shell side of the heat exchanger is further studied.The reasons for the differences in flow and heat transfer in different heat exchangers are revealed,and the distribution of velocity components and their effects on flow and heat transfer are studied.Finally,the accuracy of the numerical simulation method is verified through experimental research.The main work and research results of this paper are as follows:(1)The residence time distribution(RTD)method is used to qualitatively and quantitatively analyze the flow dead zones in different types of shell-and-tube heat exchangers.The research results show that the flow dead zones of the torsional flow heat exchanger are mainly distributed in inlet section and the corner between the cylinder wall and the baffle in the shell side of heat exchanger.The volume fraction of the flow dead zone in the shell-and-tube heat exchanger decreases with the increase of the Reynolds number.(2)By optimizing the arrangement of the tube bundle support structure of the torsional flow heat exchanger,and comparing the flow dead zone and heat transfer performance before and after optimization.The results of the research show that the ratios of dead zone volume fractions are 24.11%,27.96%and 31.65%in the reverse direction of baffle to that in the forward arrangement of the baffle respectively.Compared with the forward arrangement of the arrangement of the torsional flow heat exchanger baffle,heat transfer performance of the reverse arrangement can be improved to 12.65-13.56%.(3)Using a combination of user-defined functions(UDF)and computational fluid dynamics(CFD),the velocity component of the fluid in the shell-and-tube heat exchanger and its influence on flow and heat transfer are analyzed.The research found that the flow pattern of the torsional flow heat exchanger combines the advantages of cross flow and longitudinal flow.The difference in flow and heat transfer of heat exchanger is mainly caused by different cross flow velocity component,and the ratio of velocity components is maintained at about 0.24 to 1.51.(4)With the increase of the inclination angle of the baffle of the torsional flow heat exchanger,the internal flow pattern of the heat exchanger gradually changes from cross flow to longitudinal flow,and the heat transfer performance of the heat exchanger shows a trend of first increasing and then decreasing.When the velocity component ratio of the torsional flow heat exchanger is 0.6,the heat transfer performance of the heat exchanger shell side is increased by 3.42%to 7.65%.(5)The cold state experimental platform of the torsional flow heat exchanger has been established.The LDV was used to measure the velocity at key positions in the flow field of the torsional flow heat exchanger,and the results were compared with the numerical simulation results.The research results show that the experimental values are in good agreement with the simulated values,which further verifies the accuracy of the numerical simulation method in this paper.