Numerical Investigation of the Performance of Kenics Static Mixers for the Agitation of Shear Thinning Fluids

Mahammedi, Abdelkader; Ameur, Houari; Ariss, A.

doi:10.18869/acadpub.jafm.73.240.27314

“…The thickness of the mixer depends on the material used in the manufacture. Moreover, the screw pitch largely affects the vortex flow along the axial direction of the pipe and has a relatively small impact on the positions of the vortices along the radial direction, according to the results in a study of a Kenics mixer [37]. Thus, the screw pitch is not the primary design parameter in this study, considering that the purpose of our design based on the synergy idea is to relocate the vortices along the radial direction to approach the L/D boundary.…”

Section: Resultsmentioning

confidence: 99%

Synergy between flow and light fields and its applications to the design of mixers in microalgal photobioreactors

Qin

¹

,

Wu

²

,

Jing

³

2019

Biotechnol Biofuels

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Background Mixers are usually inserted into microalgal photobioreactors to generate vortices that can enhance light/dark cycles of algal cells and consequently enhance biomass productivity. However, existing mixer designs are usually developed using a trial-and-error approach that is largely based on the designer’s experience. This approach is not knowledge-based, and thus little or no understanding of the underlying mechanisms of mixer design for mixing performance of photobioreactors is attained. Moreover, a large pumping cost usually accompanies mixer introduction, and this cost is not favorable for practical applications. This study aims to improve this situation. Results In addition to the individual effects of flow and light fields, improving the synergy (coordination) between these fields may markedly enhance the L/D cycle frequency with a lower increase in pumping costs. Thus, the idea of synergy between flow and light fields is introduced to mixer design. Better synergy can be obtained if (a) the vortex core and L/D boundary are closer to each other and (b) the vortex whose core is too far from the L/D boundary is removed. The synergy idea has two types of applications. First, it can facilitate a better understanding of known numerical and experimental results about mixer addition. Second, and more importantly, the idea can help to develop new rules for mixer design. A helical mixer design is provided as a case study to demonstrate the importance and feasibility of the synergy idea. An effective method, i.e., decreasing the radial height of the helical mixer from the inner side, was found, by which the L/D cycle frequency was enhanced by 10.8% while the pumping cost was reduced by 23.8%. Conclusions The synergy idea may be stated as follows: the enhancement of L/D cycle frequency depends not only on the flow and light fields individually but also on their synergy. This idea can be used to enhance our understanding of some known phenomena that emerge by mixer addition. The idea also provides useful rules to design and optimize a mixer for a higher L/D cycle frequency with a lower increase in pumping costs, and these rules will find widespread applications in PBR design. Electronic supplementary material The online version of this article (10.1186/s13068-019-1430-y) contains supplementary material, which is available to authorized users.

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“…Calder and Yezzi [34] considered a rate of convergence and application for obstacle problems. In some studies mentioned therein [35][36][37][38], authors have numerically investigated the flows of incompressible non-Newtonian fluids in various computational domains. Ameur and Menni [36] performed simulations at high Reynolds numbers giving rise to a turbulent flow in a backward facing step configuration, and a comparison with the experimental studies is performed.…”

Section: Outletmentioning

confidence: 99%

Flow of the Bingham-Papanastasiou Regularized Material in a Channel in the Presence of Obstacles: Correlation between Hydrodynamic Forces and Spacing of Obstacles

Mehmood

¹

,

Mahmood

²

,

Majeed

³

et al. 2021

Modelling and Simulation in Engineering

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The numerical modeling and simulation for the stationary Bingham fluid flow around two confined circular cylinders with various gap ratios are studied. The singularity in the model’s apparent viscosity is dealt by Papanastasiou’s regularization. The model equations are discretized by adopting the methodology based on finite element method (FEM) by choosing a mixed higher order LBB-stable P 2 − P 1 finite element pair. The direct solver PARADISO has been utilized to solve the linearized system of equations. Hydrodynamic forces represented by drag and lift coefficients are computed, and a correlation coefficient is calculated for the gap ratios 0.1 ≤ G p ≤ 0.3 and for several values of the Bingham number 0 ≤ B n ≤ 50 . Line graphs for horizontal and vertical velocities are drawn. Moreover, velocity and pressure profiles are plotted for pertinent values of the parameters. Plug and shear zones are revealed via velocity snapshots in the domain. Pressure is nonlinear in the vicinity of the obstacles and becomes linear downstream in the cylinders as expected in channel flows.

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“…They direct the flow in the radial direction into the mixer walls and back to the center. Concurrently, the flow division patterns are produced and grow exponentially as the flow passes through each blade (Thakur et al 2003, Vilar et al 2017, Mahammedi et al 2017.…”

Section: Armentioning

confidence: 99%

Effect of Geometry Design on Mixing Performance of Newtonian Fluids using Helical Overlapped Mixer Elements in Kenics Static Mixer

Talhaoui

¹

,

Draoui

²

,

Youcefi

³

2021

JAFM

0

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The laminar flow pattern and mixing behavior of incompressible Newtonian fluids in different modified mixer configurations were numerically investigated using Computational Fluid Dynamics (CFD) simulations in the range of Re=0.15-100. The governing equations were solved by ANSYS Fluent 14 using the second-order finite volume method (FVM) and the SIMPLE algorithm scheme. The computational model is assessed by comparing the predicted pressure drop results to empirical correlations in the literature. The effects of incorporated helical overlapped mixer elements and the diameter aspect ratio (C) on the mixing efficiency for different mixer geometries were examined and evaluated by characteristics measures of Intensity of Segregation (IOS), pressure drop, extensional efficiency, and G-factor. The performance of new modified mixers is evaluated via comparison with the standard industrial Kenics static mixer. The static mixers with modified internal geometry achieved fast mixing and better mixing quality than the Kenics mixer. Besides, an increase in diameter aspect ratio C benefited from a decrease in pressure drop within the static. The modified mixer: C=1.5 was found to have the highest mixing efficiency, concerning short mixing length with marginally higher pressure drop than the other mixers. In contrast, the mixer: C=2 is the most efficient based on low pressure drop and energy requirement with slightly greater mixing length.

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Numerical Investigation of the Performance of Kenics Static Mixers for the Agitation of Shear Thinning Fluids

Cited by 21 publications

References 32 publications

Synergy between flow and light fields and its applications to the design of mixers in microalgal photobioreactors

Synergy between flow and light fields and its applications to the design of mixers in microalgal photobioreactors

Flow of the Bingham-Papanastasiou Regularized Material in a Channel in the Presence of Obstacles: Correlation between Hydrodynamic Forces and Spacing of Obstacles

Effect of Geometry Design on Mixing Performance of Newtonian Fluids using Helical Overlapped Mixer Elements in Kenics Static Mixer

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