Free-surface shape in unbaffled stirred vessels: Experimental study via digital image analysis

Busciglio, Antonio; Caputo, Giuseppe; Scargiali, Francesca

doi:10.1016/j.ces.2013.10.019

Cited by 60 publications

(48 citation statements)

References 16 publications

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“…The profile of the central vortex was computed by means of an iterative technique. Busciglio et al [1] measured the free-furface vortex shape generated by a Rushton turbine, Lightnin A310, and pitched-blade turbine in the unbaffled stirred vessel. Effects of impeller speeds, initial liquid filling, and impeller clearance were determined.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Gravity on the Hydrodynamics in an Unbaffled Stirred Vessel

Yang

Zhou

2015

Chem Eng & Technol

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The hydrodynamics in an unbaffled stirred vessel were simulated in order to highlight the effect of gravity on pressure and velocity distributions. Two fluids with different viscosity were studied for the laminar and turbulent flow regimes, respectively. The simulation results were compared with experimental data from the literature. Results indicate that for the higher-viscosity fluid, gravity only affects static pressure and that the effects of gravity on velocity and dynamic pressure are negligible. For the lower-viscosity fluid, however, gravity imposes a pronounced impact on static pressure, dynamic pressure, velocity, and turbulent kinetic energy. These findings indicate that careful consideration is necessary for the role that gravity plays in the study of free-surface hydrodynamics in unbaffled stirred vessels.

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Section: Introductionmentioning

confidence: 99%

“…Nowadays, the unbaffled stirred vessel receives great attention as it has advantages in certain selected applications over the baffled vessel [1,2]. For example, it is useful to draw down floating particles [3] and is effective for particle suspension [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Effect of Gravity on the Hydrodynamics in an Unbaffled Stirred Vessel

Yang

Zhou

2015

Chem Eng & Technol

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“…In unbaffled stirred tanks, centrifugal force increases the angular velocity of liquid leading to greater deformation of free liquid surface and the generation of a vortex. As impeller speed is further increased, both the width and depth of the vortex increases . At a high impeller speed, the vortex comes in contact with the impeller, and this results in the ingestion of gas in the liquid.…”

Section: Introductionmentioning

confidence: 99%

“…The vortex formation along with vortex ingestion enhances gas‐liquid dispersion. Thus, unbaffled tanks are preferred for shear‐sensitive (bioreactors), low attrition (crystallizer), and deep‐cleaning/sterilization (pharmaceutical) applications . The vortex shape and vortex ingestion are important parameters, the quantification of which is critical for design and scale‐up .…”

Section: Introductionmentioning

confidence: 99%

“…Nagata et al proposed a model for the vortex shape derived from experimental measurements of the effect of impeller speed, impeller clearance, and liquid loading on vortex shape. As this model was derived to predict the vortex shape above the impeller, it resulted in a significant discrepancy between the calculated shape and the experimental data with vortex ingestion condition . Busciglio et al introduced a velocity correction factor in Nagata et al's model to predict the vortex shape with vortex ingestion.…”

Section: Introductionmentioning

confidence: 99%

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Vortex shape and gas‐liquid hydrodynamics in unbaffled stirred tank

Prakash¹,

Bhatelia²,

Wadnerkar

et al. 2019

Can J Chem Eng

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The present study investigated the effect of impeller speed and vortex ingestion on vortex shape, gas holdup, and bubble size distribution in an unbaffled stirred tank using optical probe measurements. Further, the ability of the volume of the fluid model to predict vortex shape was examined. Without vortex ingestion, an increase in impeller speed resulted in a significant variation in vortex shape, whereas it had a negligible effect on vortex shape with ingestion. This suggests that when vortex ingestion occurred, most of the energy was consumed for the dispersion of gas rather than the deformation of the gas‐liquid interface. It was observed that a large number of gas bubbles were entrained into the vortex core around the impeller region, which led to a lower gas holdup at the top axial locations. An increase in the impeller speed also resulted in the formation of larger bubbles. The absence of baffles limits shear for bubble break up, resulting in larger bubbles above the impeller plane.

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Power consumption and form drag of regular and fractal‐shaped turbines in a stirred tank

et al. 2016

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Previous wind-tunnel measurements have shown that fractal shaped plates have increased drag compared to square plates of the same area. In this study we measure the power consumption and drag of turbines with fractal and rectangular blades in a stirred tank. Power number decreases from rectangular to fractal impellers by over 10%, increasingly so with fractal iteration number. Our results suggest that this decrease is not caused by the wake interaction of the blades, nor solely by the wake interaction with the walls either.Pressure measurements on the blades' surface show that fractal blades have lower drag than the rectangular ones, opposite to the wind tunnel experiment results. All tested blades' centre of pressure radius increases with Re, while their drag coefficient decreases, a possible effect of the solid body rotation increase with Re. Spectral analysis of the pressure signal reveals two peaks possibly connected to the blades' roll vortices.

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Free-surface shape in unbaffled stirred vessels: Experimental study via digital image analysis

Cited by 60 publications

References 16 publications

Effect of Gravity on the Hydrodynamics in an Unbaffled Stirred Vessel

Effect of Gravity on the Hydrodynamics in an Unbaffled Stirred Vessel

Vortex shape and gas‐liquid hydrodynamics in unbaffled stirred tank

Power consumption and form drag of regular and fractal‐shaped turbines in a stirred tank

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