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CFD aided investigation of single droplet coalescence

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Chinese Journal of Chemical Engineering 2016年第2期24卷 249-252页

作者： Felix Gebauer Mark W.Hlawitschka hans-jorg bart Chair of Separation Science and Technology University of KaiserslauternKaiserslautern 67653Germany Center for Computational and Mathematical Modelling(CIVY) University of KaiserslauternKaisersloutern 67653Germany

This article describes the development of a coalescence model using various CFD work packages,and is validated using as toluene water model *** studies were performed to describe droplet interactions in liquid–liquid test *** models use adjustable parameters to describe these *** research in the past decades led to different correlations to model coalescence and breakage depending on the chemical system and the apparatus *** the complexity of droplet coalescence requires a detailed investigation of local phenomena during the droplet *** fluid dynamics(CFD) studies of single droplet interactions were performed and validated with experimental results to improve the understanding of the local hydrodynamics and film drainage during *** CFD simulations were performed for the interaction of two differently sized droplets at industrial relevant impact *** experimental verification and validation of the numerical results were done with standardized high-speed imaging studies by using a special test cell with a pendant and a free rising *** experimental based algorithm was implemented in the open source code OpenF OAM to account for the contact time and the dimple *** standard European Federation of Chemical Engineering(EFCE) test system toluene/water was used for the numerical studies and the experimental investigations as *** results of the CFD simulations are in good accordance with the observed coalescence behavior in the experimental *** addition,a detailed description of local phenomena,like film rupture,velocity gradients,pressures and micro-droplet entrainment could be obtained.

关键词： CFD Parameter estimation Coalescence Film drainage

CFD based extraction column design-Chances and challenges

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Chinese Journal of Chemical Engineering 2016年第2期24卷 259-263页

作者： Mark W.Hlawitschka Menwer M.Attarakilh Samer S.Alzyod hans-jorg bart Chair of Separation Science and Technology POB 3049TU KaiserslauternKaiserslautern 67653Germany Center for Computational and Mathematical Modelling(CM2) TU KaiserslauternKaiserslautern 67653Germany University of Jordan Department of Chemical Engineering11942 AmmanJordan

This paper shows that one-dimensional （I-D） [and three-dimensional （3-D） computational fluid dynamics （CFD）] simulations can replace the state-of-the-art usage of pseudo-homogeneous dispersion or back mixing models. This is based on standardized lab-scale cell experiments for the determination of droplet rise, breakage, coalescence and mass transfer parameters in addition to a limited number of additional mini-plant experiments with original fluids. Alternatively, the hydrodynamic parameters can also be derived using more sophisticated 3- D CFD simulations. Computational 1-D modeling served as a basis to replace pilot-plant experiments in any column geometry. The combination of 3-D CFD simulations with droplet population balance models （DPBM） increased the accuracy of the hydrodynamic simulations and gave information about the local droplet size. The high computational costs can be reduced by open source CFD codes when using a flexible mesh generation. First combined simulations using a three way coupled CFD/DPBM/mass-transfer solver pave the way for a safer design of industrial-sized columns, where no correlations are available.

关键词： CFD DPBM Column design

Numerical Investigation of Particle Rebound Characteristics with Finite Element Method

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Open Journal of Fluid Dynamics 2017年第3期7卷 310-329页

作者： Mehdi Azimian hans-jorg bart Chair of Separation Science and Technology Department of Mechanical and Process EngineeringUniversity of KaiserslauternKaiserslauternGermany

In this work, investigation of particle rebound characteristics due to impact with surface of a target material is presented. The rebound of a spherical particle after impact on a planar surface was analyzed in detail. Specifically, the coefficient of restitution of the particle under various impact conditions was investigated numerically. This study has been conducted by carrying out a series of FEM-based (finite element method) simulations using ANSYS Autodyn software. First, a summary about the state of the art and the theoretical models for the elastic collisions were reviewed. Afterwards, the impact of an aluminum oxide particle on an aluminum alloy target surface was modeled. Using the Autodyn tool, the results were compared and validated by the experimental results of Gorham and Kharaz [1]. Selection of an appropriate equation of state (EOS) and a strength model for each material had a strong effect on the results. For both materials, the Shock EOS was applied for the final simulations. As the strength model, the Johnson-Cook and the elastic model were used, respectively. The agreement of the obtained numerical results with the experimental data confirmed that the proposed model can precisely predict the real behavior of the particle after the impact, when the material models are properly chosen. Furthermore, the effects of impact velocity and impact angle on the rebound characteristics of the particle were analyzed in detail. It was found that the selection of the exact value of friction coefficient has a drastic effect on the prediction of restitution coefficient values, especially the tangential restitution coefficient.

关键词： Finite Element Method(FEM) ANSYS Autodyn Single Particle Impact Restitution Coefficient Friction Coefficient

LDA Study of Particulate Flow in a Channel with Deformed Surface Locations and with Flow Conditioner

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Open Journal of Fluid Dynamics 2015年第4期5卷 353-363页

作者： Mehdi Azimian hans-jorg bart University of Kaiserslautern KaiserslauternGermany

Hydroabrasion in particulate flows plays an important role in various industrial and natural processes. To predict the effects of particulate flow and the resulting phenomena such as erosion/abrasion in a pipeline, channel or a fitting, it is essential to characterize the effects in a simple standardized geometry. For this purpose, it is vital to initially understand the particulate flow behavior and motion in such geometries. In the present work, two series of experimental works by application of the LDA measurement technique were successfully conducted. First, the particulate flow behavior at downstream of a flow conditioner inside a channel with square cross-section was investigated. Shorter lengths for fully development of velocity profile by using the self-constructed flow conditioner were observed. Moreover, the flow at downstream of the conditioner was modeled with the CFD tool (ANSYS-CFX V. 14.57) and the simulation results were compared and validated by the LDA experimental data. Better agreement between the simulation results and experimental data was observed in the fully developed region. However, there are some deviations due to the actual pressure loss through the experimental loop and the calculated pressure loss value, which includes some assumptions for the loss coefficients. Furthermore, the particulate flow behavior and vortex generation inside the deformed locations of a channel surface were studied in detail. With the help of the Matlab program, it was possible to calculate and visualize the velocity vectors for each measured point inside the channel accurately.

关键词： Channel Flow Flow Conditioner Particulate Flow CFD LDA

Investigation of Hydroabrasion in Slurry Pipeline Elbows and T-junctions

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Journal of Energy and Power Engineering 2014年第1期8卷 65-78页

作者： Mehdi Azimian hans-jorg bart Chair of Separation Science and Technology University of Kaiserslautern Kaiserslautern D-67663 Germany

The present study demonstrates the comparison of erosion rate of critical pipeline parts, namely elbow and T-junction which face the maximum erosion in a pipeline and may cause an early damage and failure of the system. CFD （computational fluid dynamics） with an Eulerian-Lagrangian approach coupled with an approved erosion model is applied to visualize the 3-D flow behavior of slurry flow in both parts and to predict the erosion rate and the location of erosion at the internal surfaces. The analysis of slurry erosion is performed in five steps; geometry and grid generation, grid study/refinement, fluid flow solution, solid particles tracking and finally, the erosion calculation. In previous publications in literature considering transportation of gas-solid flows in pipe parts, the application ofT-junctions instead of elbows for specified conditions in order to reduce the erosion is recommended. In this article, it is approved that for liquid-solid flows, the Stokes number is reasonably smaller than the values for gas-solid flows. This causes the solid particles tightly couple to the fluid phase and to travel more closely with the fluid streamlines. The effects of important influencing parameters such as feed flow velocity, solid concentration, particle size and shape are investigated in detail in current work. It was found that for liquid-solid flows, the erosion of T-junction for all of the mentioned influencing parameters, due to its geometrical specifications and Stokes number variation in comparison with gas-solid flows, is reasonably higher than erosion of elbow. Due to these findings, in contrary to the gas-solid mixture flows, application of T-junction instead of elbow for liquid-solid flow transportation is not recommended.

关键词： CFD liquid-solid mixture flow elbow and T-junction erosion rate.

Simulating Spiraling Bubble Movement in the EL Approach

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Open Journal of Fluid Dynamics 2017年第3期7卷 288-309页

作者： Andreas Weber hans-jorg bart Axel Klar Department of Separation Science and Technology TU KaiserslauternKaiserslauternGermany Department of Technomathematics TU KaiserslauternKaiserslauternGermany

Simulating the detailed movement of a rising bubble can be challenging, especially when it comes to bubble path instabilities. A solution based on the Euler Lagrange (EL) approach is presented, where the bubbles show oscillating shape and/or instable paths while computational cost are at a far lower level than in DNS. The model calculates direction, shape and rotation of the bubbles. A lateral force based on rotation and direction is modeled to finally create typical instable path lines. This is embedded in an EL simulation, which can resolve bubble size distribution, mass transfer and chemical reactions. A parameter study was used to choose appropriate model constants for a mean bubble size of 3 mm. To ensure realistic solution, validation against experimental data of single rising bubbles and bubble swarms are presented. References with 2D and also 3D analysis are taken into account to compare simulative data in terms of typical geometrical parameters and average field values.

关键词： Euler Lagrange Bubble Column Bubble Path Instability Ellipsoidal Bubble Bubble Shape Zigzag Path

Phosphate removal from wastewater by model-La(Ⅲ)zeolite adsorbents

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Journal of Environmental Sciences 2008年第6期20卷 670-674页

作者： NING Ping bart hans-jorg LI Bing LU Xiwu ZHANG Yong Department of Environmental Science and Engineering Kunming University of Science and Technology Kunming 650093 China Lehrsmhl für Thermische Verfahrenstechnik TU Kaiserslautern D-67653 Kaiserslautern Germany Department of Environmental Engineering Southeast University Nanjing 210096 China

Phosphorus is one of the primary nutrients which leads to eutrophication and accelerates aging process in enclosed water bodies. Because of the poor phosphorus selectivity of other adsorbents, the novel La（Ⅲ）-modified zeolite adsorbent （LZA） was prepared by modifying 90 nm zeolite with lanthanide to selectively remove phosphate in the presence of various omnipresent anions, such as sulfates, bicarbonates, and chlorides. Through batch and fixed bed operation, the following optimum conditions were obtained： concentration of lanthanum chloride solution 0.05 mol/L; solid/liquor ratio 1/25; pH 10; calcination temperature 550℃; time 1 h. The value of the Freundlich model constants Kf and 1/n were found to be 16.76 mg/L and 0.2209, respectively. In addition, when calculated at pH 6.0, distribution coefficient KD could be as high as 36.6. Furthermore, in the alkaline pH range, solution of 0.8 mol/L NaCl was used to regenerate the saturated LZA, which could reach the high regeneration efficiency as high as 100%. Because of the good selectivity and regenerability of LZA, it might serve as a potential way for advanced phosphate removal from the sewage containing other anions.

关键词： phosphate adsorption zeolite regeneration distribution coefficient