The Effect of a Modified Downcomer on the Hydrodynamics in an External Loop Airlift Reactor

Jones, Samuel T.; Heindel, Theodore J.

doi:10.1115/fedsm2006-98011

Cited by 3 publications

(3 citation statements)

References 17 publications

(16 reference statements)

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“…The magnitude of U Lr is similar to that report in these works for EALRs with an A d /A r ratio smaller than 0.11; however, the way in which U Lr changes with increasing U G is much different due to the unique flow conditions observed in this EALR. Therefore, any attempt to predict U Lr for this reactor using the published correlations failed primarily due to the fact that there are changing liquid flow regimes in this reactor as noted by Jones and Heindel, (2006). U Lr in the EALR for the current investigation is a function of U G with a power-law dependence in the form:…”

Section: Liquid Velocity Resultsmentioning

confidence: 89%

“…The gas flow rate is measured using a calibrated mass flow meter and the superficial gas velocity (U G ) is based on the cross-section of the riser. The gas holdup values in the riser (ε r ) and downcomer (ε d ) are calculated by the differential hydrostatic pressure method using two pressure transducers on the riser and an inclined U-tube manometer on the downcomer (Jones and Heindel, 2006).…”

Section: Experimental Conditionsmentioning

confidence: 99%

“…The linear liquid velocity in the downcomer is determined using the time interval between the conductivity signal peaks and the measured distance between the conductivity electrodes. The riser superficial liquid velocity (U Lr ) is then calculated using the method present by Jones and Heindel, (2006).…”

Section: Experimental Conditionsmentioning

confidence: 99%

See 2 more Smart Citations

The Influence of External Airlift Loop Bioreactor Configuration on Bioreactor Hydrodynamics

Jones¹,

Heindel²

2007

2007 Minneapolis, Minnesota, June 17-20, 2007

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Airlift bioreactors have the potential of being used in many fermentation processes, and understanding their hydrodynamics is key to their use. To this end, gas holdup (i.e., volumetric gas fraction) and superficial liquid velocity in the downcomer and riser are studied in an external loop airlift bioreactor with an area ratio of 1:16. Two downcomer configurations are investigated consisting of the downcomer open or closed to the atmosphere. Experiments for these two configurations are carried out, over a range of superficial gas velocities from UG = 0.5 to 20 cm/s, using three aeration plates with open area ratios of 0.62, 0.99 and 2.22%. These results are compared to bubble column bioreactors and external loop airlift bioreactors with larger area ratios for similar operating conditions. Gas holdup in both the riser and downcomer are found to increase with increasing superficial gas velocity. Experimental results show that the gas holdup in the riser does not vary significantly with a change in the downcomer configuration or bubble column operation, while a considerable variation is observed in the downcomer gas holdup. Test results also show that the maximum gas holdup for the three aerator plates is similar, but that the gas holdup trends are different. The superficial liquid velocity is found to vary for the two downcomer configurations. However, for both cases the superficial liquid velocity is a function of the superficial gas velocity and/or flow condition in the downcomer. These observed variations are independent of the aerator plate open area ratio. The superficial liquid velocity is also found to vary for both downcomer configurations when compared to external airlift loop reactors having larger area ratios.

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Section: Liquid Velocity Resultsmentioning

confidence: 89%

Section: Experimental Conditionsmentioning

confidence: 99%

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The Influence of External Airlift Loop Bioreactor Configuration on Bioreactor Hydrodynamics

Jones¹,

Heindel²

2007

2007 Minneapolis, Minnesota, June 17-20, 2007

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A Combined Numerical and Experimental Study of Hydrodynamics for an Air-Water External Loop Airlift Reactor

Law

Jones

Heindel

et al. 2011

Journal of Fluids Engineering

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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 interconnected with two horizontal tubes and is often preferred over traditional bubble column reactors because they can operate over a wider range of conditions. In the present work, the gas-liquid flow dynamics in an ELALR was simulated using an Eulerian-Eulerian ensemble-averaging method in two-dimensional (2D) and three-dimensional (3D) coordinate systems. The computational fluid dynamics (CFD) simulations were compared to experimental measurements from a 10.2 cm diameter ELALR for superficial gas velocities ranging from 1 cm/s to 20 cm/s. The effect of specifying a mean bubble diameter to represent the gas phase in the CFD modeling was investigated, and 2D and 3D simulations were found to be in good agreement with the experimental data. The ELALR flow regimes were compared for the reactor operating in bubble column, closed vent, and open vent modes, and the 2D simulations qualitatively predicted the behavior of bubble growth in the downcomer. However, it was found that 3D simulations were necessary to capture the physics of the ELALR for gas holdup, bulk density differences, and riser superficial liquid velocity. Disciplines Complex Fluids | Mechanical Engineering | Thermodynamics Comments

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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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The Effect of a Modified Downcomer on the Hydrodynamics in an External Loop Airlift Reactor

Cited by 3 publications

References 17 publications

The Influence of External Airlift Loop Bioreactor Configuration on Bioreactor Hydrodynamics

The Influence of External Airlift Loop Bioreactor Configuration on Bioreactor Hydrodynamics

A Combined Numerical and Experimental Study of Hydrodynamics for an Air-Water External Loop Airlift Reactor

Simulating Gas-Liquid Flows in an External Loop Airlift Reactor

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