3D/2D hybrid model for ribbon impellers operating in laminar regime

In the study a 3D/2D hybrid model for ribbon mixers, for a laminar range of mixing was verified. Distributions of the experimental and model values of velocity components and the experimental and model values of mixing power for this type of mixers were compared. Further on, based on the model solutions the optimum parameters of ribbon agitators due to the time of homogenization were established.     

Development of a qualitative test method for the cleanability of polymer woven filter media

In this paper a new method for cleaning of filter media is presented, and the cleanability with different textures and surface finishes is compared. With the method described, it is possible to evaluate the quality of the cleaning process. According to the German VDMA standard cleaning test, riboflavin and malt extract are applied as model contaminants for evaluation of the cleaning results. To compare the cleanability of filter media with different properties and geometries the results are adapted to the law of mass transfer and to the Sherwood number, a dimensionless parameter describing the quality of a cleaning process.     

Homogeneous dispersion of SiO2 nanoparticles in an hydrosoluble polymeric network

The main difficulty still encountered in the elaboration of polymer/silica nanocomposites is the control of the nanoparticles dispersion homogeneity and the stability of the nanoparticle dispersion in the surrounding substance. The innovative point of this work is the elaboration of hybrid networks in aqueous solution performed with ASE (alkali swellable emulsion) thickeners grafted with silica nanoparticles. The thickening ability of the polymer should favour silica nanoparticles dispersion in fluid matrices. Two ASE copolymers were realised by copolymerisation in emulsion of MA (methacrylic acid) and EA (ethyl acrylate) and/or TFEM (trifluoroethyl methacrylate). The substitution of a part of EA by TFEM gave fluorinated ASE copolymers. Their free acid functions were then coupled with different ratio of amine functionalized silica nanoparticles to afford nanocomposites. The amounts of silica nanoparticles in the copolymers were determined by thermogravimetric experiments. Depending on the silica nanoparticles/copolymer ratio in basic aqueous solutions we achieved stable translucent gel like aqueous suspensions of silica nanoparticles containing 1 wt.% of the polymer/SiO₂ nanocomposite.     

Multiphase catalytic reactors: a perspective on current knowledge and future trends

ABSTRACT

Conventional and emerging processes that require the application of multiphase reactors are reviewed with an emphasis on catalytic processes. In the past, catalyst discovery and development preceded and drove the selection and development of an appropriate multiphase reactor type. This sequential approach is increasingly being replaced by a parallel approach to catalyst and reactor selection. Either approach requires quantitative models for the flow patterns, phase contacting, and transport in various multiphase reactor types. This review focuses on these physical parameters for various multiphase reactors. First, fixed-bed reactors are reviewed for gas-phase catalyzed processes with an emphasis on unsteady state operation. Fixed-bed reactors with two-phase flow are treated next. The similarities and differences are outlined between trickle beds with cocurrent gas–liquid downflow, trickle-beds with countercurrent gas–liquid flow, and packed-bubble columns where gas and liquid are contacted in cocurrent upflow. The advantages of cyclic operation are also outlined. This is followed by a discussion on conventional reactors with mobile catalysts, such as slurry bubble columns, ebullated beds, and agitated reactors. Several unconventional reactor types are reviewed also, such as monoliths for two-phase flow processing, membrane reactors, reactors with circulating solids, rotating packed beds, catalytic distillation, and moving-bed chromatographic reactors.

Numerous references are cited throughout the review, and the state-of-the-art is also summarized. Measurements and experimental characterization methods for multiphase systems as well as the role of computational fluid dynamics are not covered in a comprehensive manner due to other recent reviews in these areas. While it is evident that numerous studies have been conducted to elucidate the behavior of multiphase reactors, a key conclusion is that the current level of understanding can be improved further by the increased use of fundamentals.     

SIMULATION OF DRYING SUSPENSIONS IN SPOUT-FLUID BEDS OF INERT PARTICLES

In spouted and spout fluid bed dryers, the suspension is spread into the bed of inert particles, covering these particles with a thin layer. As the inert particles circulate, this suspension layer is dried and must become brittle enough to break off by the particle attrition. The powder produced is then carried out by air. Problems with the spout stability, particle agglomeration and powder deposits inside the column should be overcome by controlling the drying operation. The present work is aimed at modeling and simulating the drying of suspensions, such as organic and biological pastes, in conical spout-fluid beds of inert particles. A computer program has been developed combining the air flow and particle circulation models with the mass and energy balances and the drying kinetic equations in order to describe this drying process. The effect of cohesive forces is also incorporated to the fluid flow model. Simulation results are analyzed and compared with experimental data reported in the literature. Implication of these results in drying suspensions is also discussed.     

水力旋流器流场分析与测试

利用CFD方法,采用Fluent软件对水力旋流器的流场进行了研究和分析,主要分析了水力旋流器内部速度场和流体迹线的分布特点以及随分流比的变化情况,并采用激光多普勒测速仪(LDA)对部分模拟分析结果进行了验证。     

Numerical investigation of closures for interface forces acting on single air-bubbles in water using Volume of Fluid and Front Tracking models

Closures for the drag and virtual mass forces acting on a single air bubble rising in initially quiescent pure water have been numerically investigated using direct numerical simulation techniques. A 3D Front Tracking model was used and the results were compared with simulation results obtained with a 2D Volume of Fluid model to assess the influence of the third dimension. In the simulations realistic values were taken for the physical properties, i.e., a density ratio of 800. The computed time-averaged terminal rise velocity and mean aspect ratio for individual air bubbles ranging in equivalent diameter from 1 to 10 mm rising in pure water compare well with available experimental data.     

挖掘机工作装置实验样本长度确定方法及程序系统

本文通过对某液压挖掘机工作装置实验样本长度的研究,详细讨论了样本长度的确定方法,重点分析了趋势曲线拟合法,提出了样本长度精度区间分析的方法,并在处理大量实验数据的基础上,从载荷分布及寿命估算的角度做了实际的验证.编制了应用程序,使样本长度确定至寿命估算整个过程程序化.     

振动流化床中流体力学的研究

在振动流化床冷模试验装置上,以陶瓷球、柠檬酸、尼龙1010、聚氧化乙烯等为试料,研究了一定振幅和较低开孔率下振动频率、床层高度、气速等参数对振动流化床床层压力降的影响,得出了振动使床层最小流化压力降降低的程度。还考察了振动对难以流化物料的流化性能的影响。     

Agglomeration Mechanism of Nanoparticles by Adding Coarse Fluid Catalytic Cracking Particles

The agglomeration mechanism of SiO₂, TiO₂, and ZnO nanoparticles by adding coarse fluid catalytic cracking (FCC) particles is studied. The core‐shell structure of agglomerates is revealed on the basis of experimental analyses. Nanoparticles can be fluidized by forming agglomerates of the core‐shell structure with coarse FCC particles. The porosity of core‐shell structure agglomerates and the average roundness value were found to be distinctly lower than those of pure nanoparticle agglomerates. In addition, the cohesion of the core‐shell structure agglomerates is far less than that of the agglomerates formed by pure nanoparticles. Due to the smaller porosity, irregular shape, and relatively low cohesion, the fluidization behavior of core‐shell structure agglomerates is better than that of pure nanoparticle agglomerates.