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Alternative TitleNumerical Simulation of Mass Transfer Between a Liquid Sphere and Ambient Fluid in Simple Shear Flow
Thesis Advisor杨超 ; 雍玉梅
Degree Grantor中国科学院研究生院
Degree Discipline化学工程
Keyword球形液滴   剪切流   数值模拟   传递特性
Abstract在化工、医药和冶金等过程工业中,广泛存在着多相分散体系。而这些体系往往包含着大量的分散相颗粒。清楚地认识多相系统的动量、质量和热量传递规律,是多相输送、分离和反应设备设计的关键,因此,对颗粒(包括液滴和气泡)的运动和传递规律的研究具有重要的理论和现实意义。据此,本文采用数值计算的方法,对单个球形液滴在另外一个无限大、不互溶的连续相流体中的运动和传质、传热过程进行了研究。其中,连续相流体中的运动形式限定为工业设备中常见的简单剪切流动。 当研究体系为单个球形液滴处于简单剪切场中,且离散相内部和连续相的流动为Stokes流动时,基于流体力学理论的流场解析解,本文数值求解了对流-扩散方程。分别针对连续相传质阻力控制下的颗粒外部传质和分散相传质阻力控制下的颗粒内部传质这两个过程,详细考察了Peclet准数、液滴内外粘度比两个因素对传质Sherwood准数和浓度场分布的影响规律。对模拟结果进行了分析,本文提出了适用于较大Peclet数范围内的传质Sherwood数的关联式,可对体系的传质速率进行较为可靠的预测。 当研究体系为单个球形液滴处在中等Reynolds数下的连续相中时,本文通过运用已有的流场数值解,采用同样的数值方法求解了对流-扩散方程。同样针对连续相传质阻力控制下的颗粒外部传质和分散相传质阻力控制下的颗粒内部传质这两个过程,详细考察了Reynolds数、Peclet数和液滴内外粘度比对传质Sherwood数和传递过程的影响规律。
Other AbstractDispersed multiphase systems exist widely in process industry, such as chemical, pharmaceutical and metallurgical industry. A lot of dispersed particles (drop, bubble and solid particle) are involved in these systems. A clear understanding of the transport process of momentum, mass and heat in dispersed multiphase systems is the key to transporting and separating these systems. Therefore, the study on the behavior of single particles has a fundamental significance to industrial scale-up and application. From this, numerical simulation is carried out in this work to investigate the flow and mass/heat transfer between a single liquid sphere and an ambient fluid, which is assumed to be infinite and immiscible. Here, the continuous phase is subject to simple shear flow, which is common in industrial apparatus. For the case of a single sphere immersed in simple shear flow, Reynolds number is assumed small and hence the flow field is within the creeping flow regime. By using the analytical solution of flow velocity, the convection-diffusion equation is solved for the external and internal problems. The effects of Peclet number and viscosity ratio on Sherwood number and concentration field are investigated. In terms of the numerical results obtained in this work, several new correlations are derived to predict the Sherwood numbers at finite Peclet numbers for various values of viscosity ratio. For immediate Reynolds numbers, by using the existing numerical results of flow field, the 3D convection-diffusion equation is also solved for the mass transfer outside and inside a liquid sphere. For the external and internal transport problems, effects of Reynolds number, Peclet number and viscosity ratio on Sherwood number and mass transfer are studied by numerical simulations.
Document Type学位论文
Recommended Citation
GB/T 7714
李润. 球形液滴在简单剪切流场中传质过程的数值模拟[D]. 中国科学院研究生院,2013.
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