Regime transition in viscous and pseudo viscous systems: A comparative study

Rabha, Swapna; Schubert, Markus; Hampel, Uwe

doi:10.1002/aic.14528

Cited by 31 publications

(26 citation statements)

References 38 publications

(42 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…4k, j), where large cap-bubbles are observed across the vertical development of the bubble column. A similar behavior was also observed in an early study by Wilkinson et al (Wilkinson et al, 1992) and in more recent studies (Rabha et al, 2014). In addition, at high viscosity and high U G "coalescence-induced" bubbles ( Fig.…”

Section: The Experimental Resultssupporting

confidence: 67%

“…Olivieri et al (2011) reported a stabilization of the homogeneous flow regime up to μ L =4.25 mPa s and, then, for higher viscosities, a destabilization of the homogeneous flow regime. These phenomena were also confirmed by the ultrafast electron bean X-ray tomography investigation of Rabha et al (Rabha et al, 2014) …”

Section: Influence Of Viscosity On the Flow Regime Transitionsupporting

confidence: 68%

“…The increase in the gas holdup at low viscosities and its consequent decrease at higher viscosities is in qualitative agreement with the findings from other authors (see, for example, refs. (Bach and Pilhofer, 1978;Eissa and Schügerl, 1975;Godbole et al, 1982;Khare and Joshi, 1990;Olivieri et al, 2011;Rabha et al, 2014;Ruzicka et al, 2003)). An interesting discussion concerning the contribution of the "coalescence-induced" bubbles to the gas holdup structure in highly viscous liquid phases, was proposed by Yang et al (2010), to whom the reader should refer.…”

Section: The Experimental Resultsmentioning

confidence: 99%

“…When increasing the viscosity, the tendency to coalescence prevails, creating large bubbles rising the column at a higher velocity, thus reducing the gas holdup. In particular, the "dual effect of the viscosity" was clearly observed in some experimental investigations (Bach and Pilhofer, 1978;Eissa and Schügerl, 1975;Godbole et al, 1982;Khare and Joshi, 1990;Olivieri et al, 2011;Rabha et al, 2014;Ruzicka et al, 2003), but it is not clear whether it also applies to larger bubble columns (see, for example, the fluid dynamics phenomena behind Eq. (1)) and what the reasons are behind this behavior.…”

Section: Influence Of Viscosity On the Gas Holdupmentioning

confidence: 99%

“…In highly viscous media, a bimodal population, in terms of the bubble equivalent diameter (d eq , Section 2.3.2), is observed: for example, d eq < 1 mm and d eq > 20 mm (Philip et al, 1990), 1 mm < d eq < 10 mm and 10 < d eq < 150 mm , 0.7 mm < d eq < 10 mm and d eq > 10 mm (Yang et al, 2010). Rahba et al (Rabha et al, 2014) reported bimodal bubble size distributions with large bubbles having d eq =40-45 mm. For example, for viscosities G. Besagni et al Chemical Engineering Science 158 (2017) 509-538 beyond μ L > 30 mPa-s, the contribution of the small bubbles results in a further increase of the total gas holdup with increasing viscosity (Kuncová and Zahradník, 1995), instead of the levelling at a constant value, as reported by Eissa and Schügerl (1975).…”

Section: Influence Of Viscosity On the Bubble Size Distributions And mentioning

confidence: 99%

See 4 more Smart Citations

The dual effect of viscosity on bubble column hydrodynamics

Besagni

Inzoli

Guido

et al. 2017

Chemical Engineering Science

109

View full text Add to dashboard Cite

A B S T R A C TSome authors, in the last decades, have observed the dual effect of viscosity on gas holdup and flow regime transition in small-diameter and small-scale bubble columns. This work concerns the experimental investigation of the dual effect of viscosity on gas holdup and flow regime transition as well as bubble size distributions in a large-diameter and large-scale bubble column. The bubble column is 5.3 m in height, has an inner diameter of 0.24 m, and can be operated with gas superficial velocities in the range of 0.004-0.20 m/s. Air was used as the dispersed phase, and various water-monoethylene glycol solutions were employed as the liquid phase. The water-monoethylene glycol solutions that were tested correspond to a viscosity between 0.9 mPa s and 7.97 mPa s, a density between 997.086 kg/m 3 and 1094.801 kg/m 3 , a surface tension between 0.0715 N/m and 0.0502 N/m, and log 10 (Mo) between −10.77 and −6.55 (where Mo is the Morton number). Gas holdup measurements were used to investigate the global fluid dynamics and the flow regime transition between the homogeneous flow regime and the transition flow regime. An image analysis method was used to investigate the bubble size distributions and shapes for different gas superficial velocities, for different solutions of watermonoethylene glycol. In addition, based on the experimental data from the image analysis, a correlation between the bubble equivalent diameter and the bubble aspect ratio was proposed. The dual effect of viscosity, previously verified in smaller bubble columns, was confirmed not only with respect to the gas holdup and flow regime transition, but also for the bubble size distributions. Low viscosities stabilize the homogeneous flow regime and increase the gas holdup, and are characterized by a larger number of small bubbles. Conversely, higher viscosities destabilize the homogeneous flow regime and decrease the gas holdup, and the bubble size distribution moves toward large bubbles. The experimental results suggest that the stabilization/destabilization of the homogeneous regime is related to the changes in the bubble size distributions and a simple approach, based on the lift force, was proposed to explain this relationship. Finally, the experimental results were compared to the dual effect of organic compounds and inorganic compounds: future studies should propose a comprehensive theory to explain all the dual effects observed.

show abstract

Section: The Experimental Resultssupporting

confidence: 67%

Section: Influence Of Viscosity On the Flow Regime Transitionsupporting

confidence: 68%

Section: The Experimental Resultsmentioning

confidence: 99%

Section: Influence Of Viscosity On the Gas Holdupmentioning

confidence: 99%

Section: Influence Of Viscosity On the Bubble Size Distributions And mentioning

confidence: 99%

See 3 more Smart Citations

The dual effect of viscosity on bubble column hydrodynamics

Besagni

Inzoli

Guido

et al. 2017

Chemical Engineering Science

109

View full text Add to dashboard Cite

show abstract

Simultaneous effect of particle size and solid concentration on the hydrodynamics of slurry bubble column reactors

et al. 2019

View full text Add to dashboard Cite

The simultaneous effect of particle size and concentration on the total gas holdup of slurry bubble column reactors was investigated in this work. The total gas holdup was measured for air-water-glass beads systems. Three solid concentrations and three particle diameters were used. It was found that increasing particle size at high constant concentration decreases gas holdup. Moreover, increasing solid concentration decreases gas holdup and this decreasing effect is higher for larger particles. Also, solid particles have two effects on hydrodynamics, namely, changing the viscosity and density of the liquid phase as well as hindering the bubbles from rising within the column by the collision phenomenon. Therefore, a novel correcting factor was introduced to correct the gas holdup. The hindering factor considers both the collision efficiency affected by the particle size as well as the solid concentration. A novel correlation was developed to predict the experimental data of the three-phase gas holdup.

show abstract

Efficient Control of Microbubble Properties by Alcohol Shear Flows in Ceramic Membrane Channels

Liu

Han

et al. 2017

Chem Eng & Technol

View full text Add to dashboard Cite

Efficient control of microbubbles is achieved by alcohol shear flows in ceramic membrane channels. The dependence of hydrodynamic and mass transfer properties of microbubbles on liquid viscosity was investigated in a bubble column. The multichannel ceramic membrane worked as the gas sparger, and the shear flow on the membrane surface controlled the microbubble generation. Oxygen gas and glycerin solutions with different viscosities served as gas phase and liquid phase, respectively. The microbubbles were massively generated at different liquid viscosities. With increasing viscosity, the bubble size first decreased and then increased. The dual effect of viscosity on bubble size was related to bubble coalescence. However, an impact of viscosity on gas holdup was not observed for microbubbles.

show abstract

Regime transition in viscous and pseudo viscous systems: A comparative study

Cited by 31 publications

References 38 publications

The dual effect of viscosity on bubble column hydrodynamics

The dual effect of viscosity on bubble column hydrodynamics

Simultaneous effect of particle size and solid concentration on the hydrodynamics of slurry bubble column reactors

Efficient Control of Microbubble Properties by Alcohol Shear Flows in Ceramic Membrane Channels

Contact Info

Product

Resources

About