Origin of disturbances in cocurrent gas‐liquid packed bed flows

Krieg, Dennis; Helwick, J.A.; Dillon, Paul; McCready, Mark J.

doi:10.1002/aic.690410706

Cited by 32 publications

(22 citation statements)

References 27 publications

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“…Moreover, flow hysteresis, another undesirable flow phenomenon, caused by flow maldistribution in parallel channels in a TBR, is highly influenced by initial start-up conditions and tends to abate after the entire bed is fully wetted. However, the underlying mechanism is not clearly understood and flow hysteresis cannot be well interpreted from macro-scale analyses (Krieg, Helwick, Dillon, & McCready, 1995;Lin, Juang, Chen, & Chen, 2001;Urseanu, Boelhouwer, Bosmanand, & Schroijen, 2004). Therefore, attempts have been made to understand detailed flow behavior inside the flow channels between catalyst particles.…”

Section: Introductionmentioning

confidence: 99%

Numerical study of liquid coverage in a gas–liquid–solid packed bed

Zhang

et al. 2015

Particuology

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Section: Introductionmentioning

confidence: 99%

Numerical study of liquid coverage in a gas–liquid–solid packed bed

Zhang

et al. 2015

Particuology

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“…For example, the trickle-bed reactor (TBR), in which gas and liquid reactants flow cocurrently downwards across packed solid catalyst beds, now represents an important class of multiphase reactors. The flow regime transitions in a fixed bed were traditionally investigated by experimental methods like nonlinear time analysis [13] and wall pressure fluctuations [14,15]. The multiphase flow in a fixed bed is extremely complex [5]; different flow patterns can be found, such as the gas-continuous or trickle flow at low liquid and gas rates, pulse flow at intermediate liquid and gas rates, and liquid continuous or dispersed bubble flow at higher liquid flow rates.…”

Section: Introductionmentioning

confidence: 99%

Computational Fluid Dynamics Modeling of Gas‐Liquid Two‐Phase Flow around a Spherical Particle

Feng

et al. 2013

Chem Eng & Technol

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Microscale studies, which can provide basic information for meso-and macroscale studies, are essential for the realization of flow characteristics of a packed bed. In the present study, the effects of gas velocity, liquid velocity, liquid-solid contact angle, and liquid viscosity on the flow behavior were parametrically investigated for gas-liquid two-phase flow around a spherical particle, using computational fluid dynamics (CFD) methodology in combination with the volume-offluid (VOF) model. The VOF model was first validated and proved to be in good agreement with the experimental data. The simulation results show that the film thickness decreases with increasing gas velocity. This trend is more obvious with increasing operating pressure. With increasing liquid velocity, the film thickness tends to be uniform on the particle surface. The flow regime can change from film flow to transition flow to bubble flow with increasing contact angle. In addition, only at relatively high values does the liquid viscosity affect the residence time of the liquid on the particle surface.

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“…A wide range of pulse frequencies seems possible even if those, which correspond to low saturation values, are disregarded. Krieg et al(1995) also observed that moving pulses of relatively high hold up are present in trickle-fl ow at liquid velocities well below those associated with the transition to pulsing fl ow.…”

Section: Trickling To Pulsing Flow Transition Through Periodic Flow Fmentioning

confidence: 83%

“…Two-dimensional systems have been examined by Scriven and his students Melli et al, 1990). McCready and co-workers (Helwick et al, 1990;Krieg et al, 1995) offer an alternate approach and have examined experimentally predictions from stability analysis.…”

Section: Trickling To Pulsing Flow Transition Through Periodic Flow Fmentioning

confidence: 99%

Periodic Operation of Three — Phase Catalytic Reactors

Silveston

Hanika

2004

Can J Chem Eng

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Periodic operation of three phase reactors has been explored for more than two decades. This type of forcing changes selectivity and can increase either conversion or throughput. Experiments and simulation demonstrate periodic flow interruption or variation enhances reaction rates for concurrent trickle beds provided reactants are in the gas phase or can be volatilized under bed operating conditions. Temperature excursions in trickle beds can be controlled by either flow variation or switching the feed between an inert and a reactant. Several approaches to increasing rate through faster mass transfer using flow pulsing have been studied. Pulsing flow can be induced by low amplitude modulation. Periodic switching of flow direction in airlift reactors increases gas hold up and thereby the mass transfer rate. Periodic operation of three phase reactors, thus, appears to be a fertile area for engineering research.

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Origin of disturbances in cocurrent gas‐liquid packed bed flows

Abstract: Visual, video, pressure, and

Cited by 32 publications

References 27 publications

Numerical study of liquid coverage in a gas–liquid–solid packed bed

Numerical study of liquid coverage in a gas–liquid–solid packed bed

Computational Fluid Dynamics Modeling of Gas‐Liquid Two‐Phase Flow around a Spherical Particle

Periodic Operation of Three — Phase Catalytic Reactors

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