| The shell-and-tube heat exchanger is extensively used in oil refinery, chemical engineering. The baffle, one type of them, is widely used with its high reliability and practicability. Its main part in shell side is baffle, making transverse flow, forming stagnant region of fluid, reducing efficiency of heat transfer, increasing flow resistance, having worse anti-vibration behavior, etc. Hence, a great deal of energy is wasted. To solve these disadvantages, a lot of new shell-and-tube exchangers have been actively developed for decades worldwide. The new type high efficient heat exchanger with longitudinal flow of the shell side fluid(HELFSF) is one of the best exchangers. It is conceived on the basis of chemical process, with new structure, and the systemic combination of rod-ring support, tapered flow distributor and jacket—jacketed rod-baffle heat exchanger with tapered flow distributor, making good use of the advantage of each part, enhancing the efficiency of heat transfer and prolonging the life-span.The new type heat exchanger improved in structure has more advantages with more reasonable structure, lower consumption of material and remarkable energy-saving. Because of its structure features, the temperature distribution of each part becomes more complex, making the thermal stress a key for the stress analysis of exchanger. Particularly to improve the rate of efficiency to energy, modern industries leading to direction of high operating parameters, multi-factors coupling action of more high temperature, pressure and medium erosion in its whole servicing life-span. It is an unavoidable that failure events resulted from the strength related to heat exchanger. It is a challenge problem how to ensure the safety of equipment, meanwhile control the consumption of material and energy.An evident difference is found between the new type exchanger and the common shell-and-tube exchanger in structures, only empirical methods are taken in the design of the new structure, lacking of design criterions and handbook. It is critical for safe use of heat exchangers. So a scientific design is needed to design and check structures. A detailed analysis of stress and temperature was completed in the whole structure of the new heat exchanger via the theory of elastic mechanics and the finite element method, an instructional proposal was tabled to ring slab, a key part of the exchanger. A formula calculating the stress of different thicknesses was presented, and a foundation to scientifically assess the strength was also provided.Because of the complexity of exchangers, the workload will be very huge and make it impossible accomplish the work on time if model were created by interactive means. In this paper, secondary development was performed on the basis of a business finite element program - ANSYS. Parametric auto-generation of model and auto-analysis was put into effect, therefore, model creating time is decreased largely, and the analysis period will be shortened greatly, and the contrived errors are decreased. In a summary, the second development having been done is rather valuable.The analyses and data processes of 49 models and 98 cases were implemented taking into account the variety of geometric parameters by the program compiled.The dissertation mainly works are as the following aspects:1.The theoretic deductions were applied in the H-type heat exchanger with longitudinal flow of the shell side fluid, on the basis of the analysis of theory of former heat exchanger, the theory of the new type heat exchanger had been expanded, developing the former theory further, taking into account the impact of H-type structure and expansion joint and educing the formula of the relevant axial stress.2.On the basis of the actual structure and the operating condition, lots of difficulties had been overcome, and appropriate element patterns were chosen for the analysis coupling thermal and mechanics, the whole 3D models were built directly for computing heat transfer and structure analysis, why a tube was not modeled as pipe element or simplified as equivalent beams is that these element can not satisfy the need of problem. Node number totally counts to 226483, and that of element to 260463, which belongs to a large scale computational model. Besides, the internal and external pressures, and the temperature difference between inside wall and outside wall of tube were taken into account, such model is closer to the actual condition. If the element of tube was adopted by linear element and tube element, above-mentioned effects will not be included, Therefore the precise and reliability of the thermal and stress analysis will be significantly lowered.3. In the simulation of heat exchanger, including outside shell, inside flow distributor, ring slab, tubes, tube sheet and expansion joint, though the ANSYS program has better function of geometric modeling, as the dimension of the model of exchanger is large, and the geometry is too complicated, at the same time, the coupling of temperature and structure needs be analyzed, the direct analysis of model can not be competent for problem expected, so proper simplicity needs be done. In this dissertation, the 3D model of exchanger was created by parameterized techniques, which was originated in correlated region.4.Because of the complexity of the model of the heat exchanger, each part of a heat exchanger has to be glued each other, it is difficult for meshing in the joint of the tube sheet and tubes due to a plentiful number of tubes. To solve the problem, each tube was divided into two parts with different meshes, so better meshes were acquired. This approach can be a guide for other similar complex geometry model.5.In the H-type heat exchanger with longitudinal flow of the shell side fluid, till now design methods of ring slab has not been found in exoteric literature. The research on it has been done in this paper, the referenced rule and design formula of stress for exchanger ring slab was provided.6.In this paper, reasonable calculated model on heat transfer was created in the new type structure in terms of the heat transfer theory. The analysis results of numerical simulation of heat exchanger are applicable. The effect of the stress is huge due to the differences of temperatures. It is one of difficulties in the dissertation that the valuation of temperature on heat exchanger had been verified to be reasonable.7.The techniques of analysis of model, reasonable judgement of meshes and results, effectiveness of boundary condition and so on, were checked by analyzing a simple model.8.The stress of exchanger was analyzed in cold and hot end, compared with theresults of stress in mean temperature. It showed that the temperature difference between cold and hot ends should be involved.9.0n the basis of the series of master heat exchanger (belonging to a H-type heat exchanger with longitudinal flow of the shell side fluid) in ammonia synthesis process, in the same chemical process condition, the most stress of exchanger and ring slab was analyzed in different thicknesses of ring slab and dimensions of exchanger. Figures and tables for designers use were drawn. These can be utilized in future in design of exchangers.lO.The second development up to five different dimensions of heat exchanger each other was accomplished, and the parameterized automatic generation of model, auto-meshing, automatic calculation and analysis of temperature and stress was realized, and the embedded integration of CAD/CAE was also completed. The secondary development program consists of more than 24000 lines of command, including model-creation, process calculation, meshes auto-generation, automatic analysis of temperature and stress, and the user interface totally to 6 modules.11.The formula, i.e. |
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