CFD Simulation of Flow and Axial Dispersion in External Loop Airlift Reactor

Roy, Swarnendu; Dhotre, M.T.; Joshi, Jyeshtharaj B.

doi:10.1205/cherd.05178

Cited by 44 publications

(22 citation statements)

References 29 publications

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“…Drag force is usually the most important interphase force, which is in proportion with the slip velocity between two phases. Equation (3) is commonly used to describe the drag force [18,21]:…”

Section: (3) Interphase Momentum Exchangementioning

confidence: 99%

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Modified airlift reactor with a cross-shaped internal and its hydrodynamic simulation by computational fluid dynamic method

Tao

Feng

et al. 2017

Biotechnology & Biotechnological Equipment

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(2018) Modified airlift reactor with a cross-shaped internal and its hydrodynamic simulation by computational fluid dynamic method, Biotechnology & Biotechnological Equipment, 32:1, 194-203, DOI: 10.1080/13102818.2017 A modified airlift reactor (ALR) with a cross-shaped internal was developed to achieve beneficial flow conditions for an advantageous biological process. To study the effect of introduced internal on the reactor's hydrodynamics, computational fluid dynamics simulation method was applied to predict the flow characteristics verified with experimental data. The internal introduction into a conventional ALR resulted in increased liquid velocities in the riser and the downcomer for 12% and 16%, respectively, maintaining the superficial gas velocity of 3 cm/s. The internal allowed the total gas holdup slightly decreased for 4.8%, whereas the turbulent kinetic energy in the riser was significantly reduced for 13%. The cross-shaped internal modified the flow structure in the ALR's bottom zone due to, presumably, substitution of non-elastic collisions of liquid micro-lumps moving in counter-current directions with elastic collisions of micro-lumps with the wall of the internal, reducing the energy dissipation at the U-turn of the flow. The internal unified the direction of liquid velocity vectors in the bottom zone bringing an order to the liquid momenta in the flows close to the parallel ones and thus, saving energy in the ALR's operation.

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Section: (3) Interphase Momentum Exchangementioning

confidence: 99%

“…All the definitions for the three last terms may be found in the Fluent user's guide [25]. The turbulence of the dispersed gas phase was modelled in a set of algebraic equations relating the dispersed phase turbulence quantities to those of the continuous phase [21].…”

Section: (4) Turbulence Closurementioning

confidence: 99%

Modified airlift reactor with a cross-shaped internal and its hydrodynamic simulation by computational fluid dynamic method

Tao

Feng

et al. 2017

Biotechnology & Biotechnological Equipment

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“…The airlift PBR, which is considered the most popular modification of the bubble column reactors (Roy et al, 2006), is characterized by a bubble induced flow, with an up flow channel (riser) and a down flow channel (downcomer) . The advantages of this type of PBR are: no moving parts, simplicity of construction, low power consumption, good mass and heat transfer characteristics, good solid suspensions, homogeneous shear stress distribution, rapid mixing, and, one of the most important, control over liquid circulation (Roy et al, 2006;Chisti, 1998). Aeration rates and bubble diameters are controlled via air spargers which provide optimal mixing and gas transfer in the reactor (Oncel and Sukan, 2008).…”

Section: Introductionmentioning

confidence: 99%

CFD simulation of multiphase flow in an airlift column photobioreactor

Freites¹

2014

Issue 6

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A Computational Fluid Dynamics (CFD) simulation using CFX, ANSYS 11.0, has been carried out using a multiphase flow model with an Eulerian-Eulerian approach for an airlift column photobioreactors (PBR). Transient simulations were performed for three inlet air flow, 2, 3 and 5 l min . The contours for gas holdup, air and water velocity showed that the presence of gas phase (air bubbles) is lower in the downcomer but larger in the riser, which leads to require a vigorous mixing in the riser that will be sufficient for a continuous flow. For air, velocity vectors show that they are smaller in the downcomer than in the riser. Nevertheless, water velocity vectors are organized, pointing down in the downcomer and up in the riser. Water shear stress rate contours analysis showed that, shear stress rate regions are considerably larger in the riser, but lower in the downcomer. Due to fewer restrictions to the liquid phase in the riser, a large amount of energy is dissipated by gas liquid interactions. In the downcomer region, gas phase is almost inexistent, and so are the bubble collisions. Finally, the kinetic energy is larger at the top region of the riser, meanwhile is lower at the downcomer. Similar results are observed for energy dissipation rate.

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“…A schematic of an ELALR is shown in Figure 1. The airlift reactors are preferred over traditional bubble column reactors due to well directed liquid circulation, thus facilitating the cultivation of shear sensitive organisms; as a result these reactors are widely used in the biochemical industry and for waste water treatment [ 4]. Airlift reactor hydrodynamics are studied experimentally and computationally for scale-up and design considerations.…”

Section: Introductionmentioning

confidence: 99%

“…In the past, numerous research projects have been performed experimentally [I , [5][6][7][8][9][10][11][12][13][14][15][16][17][18] and computationally [3][4][18][19] to develop a better understanding of airlift reactor hydrodynamics. Numerical simulations of airlift reactors employing an Eulerian-Eulerian two-fluid model [3][4][18][19] were surveyed and literature on Eulerian-Lagrangian simulations of airlift reactor hydrodynamics were not found.…”

Section: Introductionmentioning

confidence: 99%

Simulating Gas-Liquid Flows in an External Loop Airlift Reactor

Law

Battaglia

Heindel

2008

Volume 10: Heat Transfer, Fluid Flows, and Thermal Systems, Parts A, B, and C

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The external loop airlift reactor (ELALR) is a modified bubble column reactor that is composed of two vertical columns that are connected with two horizontal connectors. Airlift reactors are utilized in fermentation processes and are preferred over traditional bubble column reactors because they can operate over a wider range of conditions. Computational fluid dynamics (CFD) simulations can be used to enhance our understanding of the hydrodynamics within these reactors. In the present work, the gas-liquid flow dynamics in an external loop airlift reactor are simulated using CFDLib with an Eulerian-Eulerian ensembleaveraging method in two-dimensional (2D) and three-dimensional (3D) coordinate systems. In addition, models are employed for the interphase momentum transfer drag coefficient and turbulence behavior. The CFD simulations for temporal and spatial averaged gas holdup are compared to the experimental measurements of Jones and Heindel [1] who used a 10.2 cm diameter ELALR over a range of superficial gas velocities from 0.5 to 20 cm/s. The effect of specifying a mean bubble diameter size for the CFD modeling is examined. The objectives are to validate 2D and 3D CFD simulations with experimental data in order to predict the hydrodynamics in an airlift reactor for future studies on scale-up and design. ABSTRACTThe external loop airlift reactor (ELALR) is a modified bubble column reactor that is composed of two vertical columns that are connected with two horizontal connectors. Airlift reactors are utilized in fermentation processes and are preferred over traditional bubble column reactors because they can operate over a wider range of conditions. Computational fluid dynamics (CFD) simulations can be used to enhance our understanding of the hydrodynamics within these reactors. In the present work, the gas-liquid flow dynamics in an external loop airlift reactor are simulated using CFDLib with an Eulerian-Eulerian ensemble-averaging method in twodimensional (2D) and three-dimensional (3D) coordinate systems. In addition, models are employed for the interphase momentum transfer drag coefficient and turbulence behavior. The CFD simulations for temporal and spatial averaged gas holdup are compared to the experimental measurements of Jones and Heindel [I] who used a 10.2 em diameter ELALR over a range of superficial gas velocities from 0.5 to 20 cm/s. The effect of specifying a mean bubble diameter size for the CFD modeling is examined. The objectives are to validate 2D and 3D CFD simulations with experimental data in order to predict the hydrodynamics in an airlift reactor for future studies on scale-up and design.

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CFD Simulation of Flow and Axial Dispersion in External Loop Airlift Reactor

Cited by 44 publications

References 29 publications

Modified airlift reactor with a cross-shaped internal and its hydrodynamic simulation by computational fluid dynamic method

Modified airlift reactor with a cross-shaped internal and its hydrodynamic simulation by computational fluid dynamic method

CFD simulation of multiphase flow in an airlift column photobioreactor

Simulating Gas-Liquid Flows in an External Loop Airlift Reactor

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