Thermal Stress Analysis And Structural Optimization Of Fixed Tube-sheet Heat Exchanger

Fixed tube-sheet heat exchangers are widely used in various related industries due to their unique features such as simple structure,strong pressure bearing capacity,high reliability,and convenient operation and maintenance.However,engineering practice at certain processes conditions such as tube-side and shell-side fluid having a larger temperature difference,the fixed tube sheet heat exchanger due to the high temperature stress caused by the heat transfer tubes pull-off phenomenon occurs,thus influence the safe and reliable operation of the heat exchanger.In this paper,taking a fixed tube-sheet heat exchanger in an engineering practice as an example,a numerical simulation analysis of the thermal stress of the fixed tubesheet heat exchanger is carried out in response to the occurrence of tube pull-out failure.And with the results of numerical analysis based on its structural optimization,optimization of the structure for the heat exchanger design and improve the provision of technical guidance.Based on the theory of fluid-solid-heat coupling analysis of ANSYS,an integrated finite element analysis model of fixed tube-sheet heat exchanger was established based on the practical application of a certain enterprise in engineering practice,and a heat exchanger fluid-solid-heat coupling analysis was performed.In this paper,CFD method is adopted to simulate the flow field and temperature field of the simulated heat exchanger.The solid temperature data of the fixed tube-sheet heat exchanger is calculated as the temperature load,and the thermal stress analysis of the overall structure of the heat exchanger is carried out in the ANSYS structure analysis.The heat exchanger's strength assessment method was used to analyze and evaluate the stress distribution and stress concentration of the entire heat exchanger.It was shown that the maximum thermal stress is far higher than the material allowable stress for the fixed tube plate heat exchanger under the given temperature load and it is the main reason that the failure of the heat transfer tube,which fails to meet the needs of the safe operation of the heat exchanger.Aiming at the problem that the heat stress of tubes and tube plates in heat exchangers is too high,two optimization and improvement schemes are proposed for the original heat exchangers.That is,the tubes and the shell use the same material,in order to avoid a difference in linear expansion coefficient caused by excessive thermal stress;provided by expansion joints in order to reduce the axial stiffness of the housing to reduce thermal stresses.Finally,the thermal stress analysis of the optimized structure shows that the optimization results can meet the thermal stress strength requirements of the heat exchange tubes and tube sheets.