The use of momentum ratio to evaluate the performance of CSTRs

Jones, Pip N.; Özcan-Taşkın, N. Gül; Yianneskis, M.

doi:10.1016/j.cherd.2008.12.005

Cited by 14 publications

(12 citation statements)

References 7 publications

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“…The minimum t res /t m value to be chosen varied from 8.2 to 24.5, depending on the other operating conditions. Jones et al (2009) found that Residence Time Distribution (RTD) data in CSTR were best correlated by means of the impeller-to-jet momentum ratio instead of the widely used t res /t m ratio. The authors also estimated the fractional plug-flow and short-circuit on the basis of residual RTD curves.…”

Section: Introductionmentioning

confidence: 97%

Flow field and homogenization time assessment in continuously-fed stirred tanks

Busciglio

Montante

Paglianti

2015

Chemical Engineering Research and Design

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Section: Introductionmentioning

confidence: 97%

Flow field and homogenization time assessment in continuously-fed stirred tanks

Busciglio

Montante

Paglianti

2015

Chemical Engineering Research and Design

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“…The momentum number Mo , is a relatively new concept which has been introduced by several authors 22–24. Bhole23 compared two axial flow impellers for pulp fiber suspensions in the laminar and transitional regimes, where both the power number and axial thrust number (similar to Mo ) are functions of the Reynolds number.…”

Section: Introductionmentioning

confidence: 99%

“…Bhole23 compared two axial flow impellers for pulp fiber suspensions in the laminar and transitional regimes, where both the power number and axial thrust number (similar to Mo ) are functions of the Reynolds number. Jones24 used the ratio of the inlet pipe momentum to the impeller discharge momentum to balance the flow and eliminate short circuiting in a CSTR. Grenville22 successfully compared blend times in a jet mixed vessel and an impeller mixed vessel in terms of momentum.…”

Section: Introductionmentioning

confidence: 99%

Impeller characterization and selection: Balancing efficient hydrodynamics with process mixing requirements

et al. 2011

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Current literature relies almost exclusively on the power number to compare and characterize impellers. Industrial mixing requirements may rely on conditions far away from the impeller. A protocol is proposed to compare impellers designed for turbulent mixing on the basis of impeller hydrodynamic performance and mixing process objectives. A hydrofoil impeller (KPC), and a mixed‐flow impeller (45° down‐pumping PBT), each at two diameters, were used to test the protocol. Fourteen measures were considered. Five are recommended for full characterization: power number, momentum number, and peak rate of dissipation of turbulent kinetic energy to characterize conditions at the impeller; power at just‐suspended speed to compare the efficiency of solids suspension at the bottom of the tank; and point of air entrainment as a measure of turbulence penetration to the free surface. These five measures provide complete information about mixing performance and good differentiation between the impellers and geometries. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2573–2588, 2012

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“…They also found that for the design of an ideal mixer, a line from the inlet to the outlet should pass through the impeller. Jones et al (2009) evaluated the performance of the continuous-flow mixing using a momentum ratio (a ratio of impeller discharge momentum to inlet jet momentum) and found that a momentum ratio of above 100 was required to achieve a perfectly mixed CSTR.…”

Section: Literature Review On Continuous-flow Mixingmentioning

confidence: 99%

Using tomography, CFD, and dynamic tests to study the continuous-flow mixing of yield-pseudoplastic fluids

Patel¹

2021

Preprint

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The major technological challenges faced by modern chemical industries are non-ideal flows such as dead zones and channeling encountered in the mixing of fluids with complex rheology. These cause sub-optimal mixing and lead to low quality products and high costs of raw materials. Therefore, the core objectives of this study were to develop methodology and tools to design an efficient continuous-flow mixing system for the fluids with complex rheology using electrical resistance tomography (ERT), computational fluid dynamics (CFD), and dynamic tests. The xanthan gum solution, which is a pesudoplastic fluid with yield stress, was used to study the dynamic behavior of the continuous-flow mixing process. The power consumption, cavern size, mixing time, and the extents of channelling and the fraction of fully mixed volume were successfully determined using dynamic tests, ERT tests, and CFD simulations and used as mixing quality criteria. A novel and efficient method was developed for flow visualization in the continuous-flow mixing of opaque fluids using 2D and 3D tomograms. A unique study on identifying the sources of flow non-ideality in non-Newtonian fluids with yield stress was done by visualizing the flow pattern inside the continuous-flow mixing vessel using 2D and 3D tomograms. The deformation of the cavern was analyzed and quantified in the continuous-flow mixing system for yield-pseudoplastic fluids using ERT. Moreover, the cavern volume was compared with the fully mixed volume and it was found that the latter was higher due to the extra momentum induced by the inlet-outlet flow. A novel study on exploring the effect of the rheological parameters of the pseudoplastic fluids with yield stress on the non ideal flows in a continuous-flow mixing system was performed using CFD. The CFD results revealed that the mixing quality was improved when the degree of the shear thinning was increased. The ratio of the residence time to the batch mixing time was evaluated to achieve ideal mixing for the continuous-flow mixing of yield-pseudoplastic fluids using dynamic tests and ERT. It was found that the ratio of residence time to the batch mixing time should be at least 8.2 or higher to achieve ideal mixing.

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The use of momentum ratio to evaluate the performance of CSTRs

Cited by 14 publications

References 7 publications

Flow field and homogenization time assessment in continuously-fed stirred tanks

Flow field and homogenization time assessment in continuously-fed stirred tanks

Impeller characterization and selection: Balancing efficient hydrodynamics with process mixing requirements

Using tomography, CFD, and dynamic tests to study the continuous-flow mixing of yield-pseudoplastic fluids

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