Numerical Analysis of Predeformation and Stress Characteristics of Prestressed Fixed Tube Sheet Heat Exchangers
In order to implement the prestressed heat exchanger technology, a numerical study was carried out on the temperature difference stress and deformation distribution characteristics of the components in the fixed tube-sheet heat exchanger under pre-deformation, which were constrained by mutual deformation. Drawing on the new numerical simulation method of fluid mechanics and heat transfer of heat exchangers based on “segmental modeling and overall synthesis”, the temperature field of heat exchangers is obtained by CFD and used as the boundary condition of ANSYS structural analysis, and the pre-tension unit is used to apply the pre-deformation and control to obtain the thermal-structural coupling analysis results. The numerical simulation results are in good agreement with the experimental data, indicating that the adopted research method is reasonable and feasible. In addition, both the experimental and numerical analysis results confirm that by reasonably applying and controlling the pre-deformation amount, the deformation constraints between the various components (tube sheet, shell, tube bundle) of the fixed tube sheet heat exchanger during operation can be effectively alleviated and coordinated , so as to create a good operating environment, and ultimately improve the operational reliability and service life of the heat exchanger.
The thermal stress caused by the shell-and-tube temperature difference of the shell-and-tube heat exchanger is the main reason for the failure of the fixed tube-sheet heat exchanger, and the general experience is that when the shell-and-tube wall temperature difference exceeds 50 ℃, the heat exchanger should be heated. Compensation measures to relieve thermal stress due to excessive temperature difference. In order to eliminate or reduce the influence of thermal stress, many solutions have been proposed theoretically and practically, and the prestressed heat exchanger is a targeted solution. The manufacturing technology of the prestressed heat exchanger using reverse deformation is proposed. The technology first uses numerical analysis to calculate the maximum temperature differential expansion that may be generated by the shell and tube of the heat exchanger, and applies appropriate reverse prestressing during the manufacturing process of the heat exchanger. Deformation to offset or reduce the thermal stress of the temperature difference generated during the operation of the heat exchanger.
Due to the complexity of the shell-and-tube heat exchanger structure, the numerical analysis method is mostly used in the analysis and research on the thermal stress of the heat exchanger. Less researched. The performance analysis of heat exchangers using pre-deformation technology is less studied. In this paper, a new CFD simulation method of “segmental modeling and overall synthesis” is used. The temperature field obtained by CFD is used as the boundary condition of the finite element analysis software ANSYS for structural analysis, and the pre-tension element is used to apply and control the amount of pre-deformation, so as to obtain the results of thermal-structural coupling analysis. Finally, the finite element results and experimental test data are obtained. In contrast, the stress characteristics of tube sheets and heat exchange tubes under pre-deformation are studied and explored. The research results show that by applying pre-deformation, the stress peak value caused by the temperature difference between the shell side walls of the heat exchanger in operation can be greatly reduced, the safe operating environment of the fixed tube sheet heat exchanger can be effectively improved, the working life of the tube sheet tube can be prolonged, and the The operational reliability of the heat exchanger is improved.