Gas hold‐up and bubble behavior in an upflow packed bed column in the limit of low flow rate

Taghavi, Mahsa; Balakotaiah, Vemuri

doi:10.1002/aic.16624

Cited by 10 publications

(12 citation statements)

References 11 publications

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“…We refer to this flow regime as the "large bubble" (LB) regime. This regime is like that observed in normal gravity (at low Bond numbers) co-current up-flow at stationary or very low liquid flow rates and low gas flow rates 6 (except that the bubbles appearing in microgravity are larger). The pressure trace in Figure 3A shows a uniform pressure signal with several spikes correlating to the release of large bubbles trapped in the packing.…”

Section: Experiments and Test Conditionssupporting

confidence: 72%

Gas–liquid flows through porous media in microgravity: Packed Bed Reactor Experiment‐2

et al. 2022

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Modifications were made to the Packed Bed Reactor Experiment (PBRE) and flown on the International Space Station as PBRE-2 to eliminate external pressure oscillations at higher liquid flow rates and the packing diameter was reduced to increase the pressure gradient for lower flows. It is found that gas hold-up is a function of bed history at low liquid and gas flow rates whereas higher gas hold-up and pressure gradients are observed for the test conditions following a liquid only pre-flow compared to the test conditions following a gas only pre-flow period. Over the range of flow rates tested, the capillary force is the dominant contributor to the pressure gradient, which is found to be linear with the superficial liquid velocity but is a much weaker function of the superficial gas velocity and varies inversely with the particle diameter.

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Section: Experiments and Test Conditionssupporting

confidence: 72%

Gas–liquid flows through porous media in microgravity: Packed Bed Reactor Experiment‐2

et al. 2022

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“…That is because for a gas bubble in a stationary packed bed, two main forces act: surface tension and buoyancy. Surface tension force tends to push the bubble downward, while buoyancy force tends to push the bubble upward 9 . The Bond number ( Bo ) is defined as the ratio of buoyancy force to surface tension force:

Bo = \frac{ρ_{normall} {italicgd}_{normalp}^{2}}{σ}

…”

Section: Resultsmentioning

confidence: 99%

“…Surface tension force tends to push the bubble downward, while buoyancy force tends to push the bubble upward. 9 The Bond number (Bo) is defined as the ratio of buoyancy force to surface tension force:…”

Section: Gas Holdupmentioning

confidence: 99%

“…A great decrease in mean bubble diameter and an obvious gas holdup are observed with the presence of packing compared to empty column, and the mean bubble diameter is reported to increase with the increasing of packing size, while decrease with increasing of gas and liquid flow rates. Taghavi and Balakotaiah 9 demonstrated experimentally the nonmonotonic behavior of the gas hold‐up in the packed bubble column in the limit of low gas flow rate with various size from 0.5 to 4.9 mm. The experiment results confirm two pattern of bubble behavior based on the magnitude of the Bond number, and bubble to particle diameter ratio is found to scale inversely with Bond number.…”

Section: Introductionmentioning

confidence: 99%

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Packing size effects on the liquid circulation property in an external‐loop packed bubble column

2022

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Packing size effects on the fluid dynamics in an external-loop packed bubble column with Raschig rings of three different effective diameters (4.9, 14.1, and 40.7 mm) in the riser were investigated. The overall gas holdup, liquid circulating velocity and gas-liquid mass transfer coefficient were respectively measured by volume expansion, tracer-response, and dynamic oxygen-absorption techniques. CFD simulation with the Euler-Euler two-fluid method was used to predict the liquid circulating velocity by treating the packing as a porous medium. Compared to the empty column, the gas holdup was found to increase in the presence of packing, however, the liquid circulating velocity and gas-liquid mass transfer coefficient are rather complicated.Specifically, the gas holdup increases with the decrease of packing size, while the liquid circulating velocity is on the contrary, and the maximal gas-liquid mass transfer coefficient is achieved under packing diameter of 14.1 mm.

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“…This flow regime can also be observed in normal gravity gas–liquid two‐phase up‐flows in packed‐beds but requires that the Bond number be much smaller than unity. For example, normal gravity experiments 21 have shown that the ratio of the bubble to packing particle diameter is inversely proportional to the Bond number (

Bo = \frac{ρ_{L} g d_{p}^{2}}{σ}

). In microgravity, the Bond number approaches zero indicating that the bubble diameter can be very large compared to the packing size.…”

Section: Summary and Discussionmentioning

confidence: 99%

Gas–liquid flows through porous media in microgravity: The International Space Station Packed Bed Reactor Experiment

et al. 2020

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Experimental results on pressure drop and flow patterns for gas–liquid flow through packed beds obtained in the International Space Station with two types of packing are presented and analyzed. It is found that the pressure drop depends on the packing wettability in the viscous–capillary (V–C) regime and this dependence is compared with previously published results developed using short duration low‐gravity aircraft tests. Within the V–C regime, the capillary contribution is the dominant force contributing to the pressure drop for the wetting case (glass) versus the viscous contribution dominating for the non‐wetting case (Teflon). Outside of the V–C regime, it is also found that hysteresis effects that are often strong in normal gravity gas–liquid flows are greatly diminished in microgravity and pressure drop is nearly independent of packing wettability. A flow pattern transition map from bubble to pulse flow is also compared with the earlier aircraft data.

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Gas hold‐up and bubble behavior in an upflow packed bed column in the limit of low flow rate

Cited by 10 publications

References 11 publications

Gas–liquid flows through porous media in microgravity: Packed Bed Reactor Experiment‐2

Gas–liquid flows through porous media in microgravity: Packed Bed Reactor Experiment‐2

Packing size effects on the liquid circulation property in an external‐loop packed bubble column

Gas–liquid flows through porous media in microgravity: The International Space Station Packed Bed Reactor Experiment

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