Research On Nonaxisymmetric Tube And Shell Heat Exchanger Structure Analysis And Improvement

In this thesis, the heat exchanger was summarized, current strength calculation method and theory of tube and shell heat exchanger were expounded, and the application of Finite Element Analysis (FEA) in heat exchanger design was displayed. As for the heat exchanger, whose tubes were disposed on tubesheet non-axial-symmetrically, current calculation formula cannot check its strength;only numerical value method can calculate its stress. By using FEA, the structure stress analysis and design improvement of this heat exchanger with irregularly shaped tubesheet were studied here;in addition, relative strength calculation formulas were deduced theoretically.The solid temperature field FEA theory was introduced on the whole, and the FEA model about this heat exchanger structure temperature field analysis was set up in reason. After calculation, the structure temperature field distribution pattern on heat exchanger was summarized, a larger different temperature between structure's parts was found, and it is likely to engender a higher temperature stress. Meanwhile, the difference between two results under different boundary condition was compared.A few kinds of FEA model about heat exchanger structure stress analysis were discussed, and the model to solve this thesis's problem was put forward: tube was simulated by truss element and other parts of structure were simulated by solid element. The structure stress field and temperature field FEA model are consistent, and this model ensures the veracity of calculation, reduces calculation element and node size, meanwhile, accord with state criterion and mechanics principle. Under 5 load cases, the stress analysis was made, and the stress distribution feature on global heat exchanger structure and local tubesheet, and the pulling away force on tube were summarized. Meanwhile, it is find that structure strength checkage was not passed, and direction ideas were put forward for the future structure design improvement.Stress analysis and strength checkage on the heat exchanger structure with thickened shell were made, and the calculation result was analyzed and summarized. By analyzing structure stress under temperature load and other force load in operation load case, the phenomena that uneven distributed temperature load plays an important role on structure stress for the heat exchanger with irregularly shaped tubesheet was found. Changing thickness of tubesheet, FEA was made;it is find that there are a different rule of stress scale on the joint between tubesheet and shell under temperature load, other force load, and operation condition load.According to analysis research result above, based on previous heat exchanger structure design, the improvement was made by adopting 4 measures: decreasing thickness of tubesheet, welding ribs between flange (as a part of tubesheet) and shell, and etc. Thereafter, the stress analysis and strength checkage about this new design structure were made, and the new one meets all demand on stress safety, and it was applied in engineering practice.When tubesheet and shell have a different temperature, according to plate and shell mechanics theory, the internal force and displacement calculation formulas about tubesheet and shell under temperature load and restraint reaction were gotten. Thereafter, the restraint reaction calculation formulas were deduced according to the condition of deformation compatibility at the joint between tubesheet and shell, and the internal force and displacement calculation formulas about tubesheet and shell were gotten consequently. Compared with FEA result in example, the validity of these formulas was proved.One U-tube heat exchanger structure FEA model was set up. and stress analysis was made under 4 load cases, strength checkage about tubesheet membrane stress, membrane + bend stress and tube pulling away force were made, and stress distribution feature on global tubesheet, local tube bridge and strength checkage were summarized.