Advance Study On Finite Element Analysis For The Fixed Tubesheet Stress Of Heat Exchanger

A brief review is made for the status of art consuming the development and the standardization of the tubular heat exchanger, and emphasis is made on the method for the calculation of the strength of the fixed tubesheet. A finite element simulation scheme was proposed for the tubular heat exchanger assembly for evaluating the stress distribution in the tubesheet, which was proved to have the merits of overcoming the limitation of current standards.The history of the finite element method is reviewed briefly. The method of adopting axisymmetric one-dimensional degenerated plate element simulating the elastic foundation , adopting axisymmetric one-dimensional degenerated shell element simulating the shell and the channel .adopting conventional 8-noded isoparametric plannar element simulation the flange, adopting axisymmetric one-dimensional degenerated shell element or the spring element simulating the bellow, adopting the spring element simulating the bolt and adopting the special transition element for connecting degenerated and axisymmetric plannar elements of the fixed tubesheet exchanger is expounded. Thus whole system consisted of tube bundle-tubesheet-flange -shell -bellow is simulated by a finite element mesh system. The method is more flexible ,yields results with satisfactory accuracy , and annular tubesheets and tubesheets with more than one annular perforated zones can be treated without difficulties.As a remedy of overcoming the drawbacks and limitations of coding of the finite element system by using FORTRAN, the object-oriented programming approach was selected. The special features of object-oriented method was described. The method of and considerations involved in the developing of a finite element program for static structural analysis by using object-oriented programming (OOP) techniques is presented. The classes and the subclasses used in the programming are explained, current work is confined to linear elastic constitutive relation of material, yet the advantages of better extendibility and maintainability as compare to the programming by using conventional procedural language such as FORTRAN are obvious. A finiteelement program for axisymmetric bend thin plate structure is taken as an example to explain the merits of object-oriented programming (OOP) techniques. VC++ language was used in the program. Better extendibility and maintainability of the developed program implies the OOP approach is promising. Otherwise, it has been realized that using OOP is more flexible and more difficult for the programmer of FORTRAN. The integrated development environment of Microsoft Visual C++ 5.0 is simply described. A finite element analysis system for calculating the stresses of the fixed tubesheet heat exchangers adopting the object-oriented approach has been developed by two project. It has been proved that development of the system is more flexible, and the program and workload rested with the understanded for this system and establishment object of the system. This system is provide with:1. The WINDOWS interface can be handled briefly.2. The OOP for finite element system is more credible, and conceal inner.3. The system is more flexible, yields results with satisfactory accuracy , and annular tubesheets and tubesheets with more than one annular perforated zones can be treated without difficulties.4. The system has better extendibility.5. Easy to learn and easy to use, more efficacy and more security.The meaning of "thin tubesheet" is explained. The special features and structure types are described. An expression for the stresses of the "thin tubesheet" structure is brought forward. A series of the "thin tubesheet" structure of different geometry was calculated by using the finite element code for the fexed tubesheet heat exchangers developed in this thesis. Using the RBF neural network for the stresses system of perforated and unperforated zone of the "thin tubesheet" has been identified. Good recall, generalization results and expressions for the stresses of perforated and unperforated zone the "thin...