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Alternative TitleNumerical Simulation of Fluid Flow in Stirred Tanks and Investigation of Surface Aeration
Thesis Advisor毛在砂
Degree Grantor中国科学院过程工程研究所
Place of Conferral中国科学院过程工程研究所
Degree Discipline化学工艺
Keyword搅拌槽 各向异性湍流模型 电导探针法 表面曝气 反应器 数值模拟
Other AbstractStirred tank reactors are widely used in chemical -industry, solvent extraction, environmental protection engineering and fermentation processes. Up till recently, empirical correlations have been used as tools for design, scale-up and operation of stirred tanks. In view of the complex turbulent three-dimensional flow in stirred tanks, these empirical relations are clearly inadequate. To fully understand the processes occurring in stirred tanks, mathematical modeling and experimental research of local hydrodynamic behavior are desired. This dissertation is devoted to the above tasks. In accordance to the anisotropic feature of turbulent flow, an anisotropic k-s turbulence model and an anisotropic algebraic stress model are adopted to predict the turbulent flow field and turbulent characteristics generated by a Rushton disc turbine with the improved inner-outer iterative procedure. The predicted turbulent flow is compared with experimental data and the simulation by the standard k-e turbulence model. The anisotropic turbulence models are found to give better prediction than the standard k-s turbulence model. The predicted turbulent flow field is in accordance to experimental data and the trend of turbulence intensity can be effectively reflected in the simulation, especially at near impeller tip locations. The distribution of turbulent shear rate in the stirred tanks is simulated with the established numerical procedure. Accurate interfacial models are needed in the simulation of the two-phase flow in a gas-liquid stirred tank based on the two-fluid model. Different drag coefficient equations are tested in predicting the mean velocity of gas and liquid and the gas fraction in order to choose a simple and reasonable drag force equation. The drag force and the virtual mass force in the bulk region and the impeller stream region are examined and analyzed. It is suggested that the virtual mass force is not negligible and should be included in the model. The drag force and virtual mass force are adopted to predict the distribution of gas holdup and velocity components of gas and liquid. The results demonstrate that the model including the virtual mass force gives better prediction of the gas holdup and has little effect on the prediction of the velocity of liquid. The gas holdup in surface aerating operation is measured with a conductance probe, and the systematic experimental data at different operating conditions are obtained. The experiment operaions are simulated numerically with a tentative rate equation of gas uptake as a function of the local hydrodynamics. The gas holdup prediction are found to fit rather well with experimental results near the surface, but the prediction is lower than the experimental data at the other region due to the imperfection of the present model.
Document Type学位论文
Recommended Citation
GB/T 7714
孙海燕. 搅拌槽内流场数值模拟和表面曝气的研究[D]. 中国科学院过程工程研究所. 中国科学院过程工程研究所,2003.
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搅拌槽内流场数值模拟和表面曝气的研究 孙(11025KB) 限制开放CC BY-NC-SAApplication Full Text
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