| The analysis and research of fluid flow and heat transfer in heat exchangers are helpful in the development of safe, high efficiency and economical heat exchanger structure. In conventional research of heat exchangers, experimental method is mostly employed. However, it cannot keep pace with the requirement of research and development of heat exchangers because of its intrinsic disadvantages such as high experimental expense, long period, strict limit, complication in model transition, difficulty of getting detailed information, etc. Currently, with the advancement of computational fluid dynamics, computational heat transfer and computer technology, it is possible to use numerical simulation method to analyze and study heat exchangers. As numerical simulation method is used more widely, more and more people are getting to think that numerical analysis is a feasible approach to save investment and decrease waste and employ it in scientific research.It is an important topic to carry out further study on high efficiency energy-saving heat exchangers with longitudinal flow of shellside fluid(HELFSF). Based on the research of gross structure of HELFSF equipments, our research center optimizes it and develops a new structure which is the combination of rod-ring(rod grid, ring) support, tapered flow distributor and jacket—jacketed rod-baffle heat exchanger with tapered flow distributor. It is demonstrated in industrial practice that the new type HELFSF has higher heat transfer efficiency with comprehensive parameter α / Δp 50% up and lighter weight 20%-40% down. At present, the new type HELFSF has been used widely in industrial production and brought distinct economic and social efficiency.The setup of flow distributor is a new structure developed to enhance the heat transfer efficiency of shell-and-tube heat exchangers and improve shellside structure. By installing flow distributor, not only the direct impact of high speed fluid on tube bundle at inlet can be prevented but also the distribution of shellside fluid can be improved. As a result, the heat transfer area of tube bundle near inlet can be used fully and the possible flow-induced vibration near inlet can be prevented. Due to the complexity of conventional flow distributor, our research center has developed the jacketed tapered flow distributor, which simplifies greatly the conventional structure of flow distributor. Since tapered structure is used in the flow distributor, the inlet has a sloping section which overcomes the shortcoming of conventional flow distributor that the fluid resistance of media entering shellside is different and makes fluid enter the shell more uniformly. Presently, there is no standard to comply with for the parameters of the new structure such as the length of high and low end of the flow distributor, etc. However, it is certain that the high end of the flow distributor must cover the inlet. Because such flow distributor is used increasingly widely in industry, it has become the emphasis of research on flow distributor to make certain the structural parameters and optimize the structure.In the paper, the numerical simulation method is employed to compute, analyzeand compare the fluid flow condition in the new type flow distributor setup of HELFSF—jacketed tapered flow distributor. Further optimal design is carried out according to the flow condition of fluid in the flow distributor.The main work and innovative points in the paper are as follows:1. In the paper, three-dimensional numerical simulation of fluid flow in the jacketed tapered flow distributor of new type HELFSF is accomplished for the first time, which is not found in previous work by others.2. In the paper, large universal commercial CFD software—FLUENT is employed to study the characteristics of fluid flow in the flow distributor of new type HELFSF. The detailed information and law of fluid flow in flow distributor are obtained. Based on this, the optimized structure of flow distributor is also presented.3. In the paper, the effect of the alteration of structural parameters in the jacketed tapered flow distributor of new type HELFSF on the uniformity of internal fluid flow is analyzed. The relationship between structural parameters of flow distributor and fluid flow condition at the inlet of shellside inner tube is obtained and the optimal parameter series are gathered, which provides some reference for the structural design of flow distributor. Such work is not reported in previous papers.4. In the paper, graphic display and statistical calculation are combined to process the results of numerical simulation. Graphic display of the results can help people understand simulated results intuitionally, clearly and qualitatively, while statistical calculation of the results make it convenient to compare, analyze, generalize the results quantitatively and get some numerical relationship. The combination of graphic display and statistical calculation preserves both the visualization of graphic display and the objective exactitude, which is seldom reported in relevant papers.5. In the paper, hybrid unstructured mesh is not used merely because of the complexity of geometry, which is generally used in the meshing of complex geometry. Although the hybrid unstructured mesh has good adaptability to geometric shape of model, its intrinsic deficiencies such as non-guarantee of mesh quality, high occupation of computer memory, high demand for computer hardware and so on limit its application. In the paper, in order to ensure the precision of calculation results, structured mesh is mostly used in view of the mesh quality and unstructured mesh is only used in few part of the model. This meshing method is not often used in relevant papers, but it provides some reference for the meshing of other complex geometric model.The main work and conclusions in the dissertation are as follows:1. Large commercial CFD software—FLUENT is employed to carry out numerical calculation. Fluid flow condition and law in flow distributor of new type HELFSF under different structural parameters (D, L> 0^ Tn H) are obtained.2. By the analysis, calculation and comparison of flow field and uniformity of mass distribution at inlet section of tapered flow distributor under different operating conditions and different structural parameters, the optimal L-0 series with best uniformity under different shell diameter, different media and different Re number.Meanwhile, the influence of L> 6 > 1\ H on the uniformity is also analyzed and the optimization design method of the jacketed tapered flow distributor is presented to provide reference for the further research and engineering application of this new type flow distributor setup.3. The method of numerical simulation in the paper and relevant empirical suggestion are also applicable for the numerical simulation of other relevant models besides the model of flow distributor in new type HELFSF.
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