Effect of geometry on the mechanisms for off-bottom solids suspension in a stirred tank

Ayranci, İnci; Machado, Márcio B.; Madej, Adam Martin; Derksen, J. J.; Nobes, David S.; Kresta, Suzanne M.

doi:10.1016/j.ces.2012.05.028

Cited by 69 publications

(28 citation statements)

References 17 publications

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“…It appears that the bronze particles need more turbulence to be suspended and this can be provided more easily by the PBT than the KPC. The glass beads are less dense; therefore, the turbulence is not as necessary and the high‐flow KPC gives a better performance 69. Overall the D = T/2 impellers consume more power at N js than the D = T/3 impellers.…”

Section: Resultsmentioning

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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Section: Resultsmentioning

confidence: 99%

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

et al. 2011

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“…14.11 and 14.12, which represent dimensionless volume flow rates through the impeller's crosssection and can be used to estimate the circulation time within bioreactors (Liepe et al 1998), were predicted to be 0.4 and 0.77 respectively. These values are within the range of conventional stirrers, for which primary flow numbers between 0.17 and 1.27 have been reported (Patwardhan and Joshi 1999;Patwardhan 2001;Kumaresan and Joshi 2006;Ayranci et al 2012). Furthermore, a primary flow number of 0.7 for the 'Elephant ear' impeller was obtained in a baffled tank, where the axial flow is enhanced by the lower tangential circulation (Zhu et al 2009).…”

Section: Stirred Rigid Systemsmentioning

confidence: 85%

Single-Use Bioreactors for Animal and Human Cells

et al. 2014

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Single-use (SU) bioreactors are being increasingly used in production processes based on animal (i.e. mammalian and insect) and human cells. They are particularly suitable for the production of high-value products on small and medium scales, and in cases where fast and safe production is a requirement. Thus, it is not surprising that SU bioreactors have established themselves for screening studies, cell expansions, and product expressions where they are used for the production of pre-clinical and clinical samples of therapeutic antibodies and preventive vaccines. Furthermore, recent publications have revealed the potential of SU bioreactors for the production of cell therapeutics using human mesenchymal stem cells (hMSCs).This chapter provides a perspective on current developments in SU bioreactors and their main applications. After briefly introducing the reader to the basics of SU bioreactor technology (terminology, historical milestones and characteristics compared to their reusable counterparts) an overview of the categories of currently available SU bioreactor types is provided. SU bioreactor instrumentation is then examined, before discussing well-established and novel applications of SU bioreactors for animal and human cells. This includes descriptions of the engineering characteristics of often-used types of SU bioreactors, covering wave-mixed, stirred, orbitally shaken systems and fixed-bed systems. In this context, the scaling-up of geometrically and non-geometrically similar SU bioreactors is also addressed.

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“…Erosion of granular beds by a shear flow is very common in natural and engineered systems; river and sea beds (Parker, 1990), pipelines transporting slurries (Gillies & Shook, 2000), dredging applications (Miedema, 2012), and solids suspension processes in mixing tanks (Ayranci et al, 2012) are only a few examples. All of these systems show a strongly inhomogeneous solids distribution and, as a result, an inhomogeneous flow pattern with relatively low velocities in and closely above the bed, and much higher velocities far away from the bed.…”

Section: Introductionmentioning

confidence: 99%

Simulations of granular bed erosion due to a mildly turbulent shear flow

Derksen

2015

Journal of Hydraulic Research

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Three-dimensional, time-dependent simulations of the erosion of a granular bed consisting of monosized, non-cohesive spherical particles are reported. The simulations fully resolve the turbulence and the flow around each of the spheres (particle-resolved, direct simulations). The erosion is due to the turbulent flow of a Newtonian liquid in a planar channel with a Reynolds number based on wall shear velocity and channel height of 168. The main control parameter in the simulations is the Shields number that was varied between 0.03 and 0.60. The simulations were performed by means of a lattice Boltzmann scheme supplemented with an immersed boundary method to impose no-slip conditions at the particle surfaces. The results show the impact of the Shields number on the mobility of the particles at the top and above the bed. They also show a strong coupling between solids motion and the strength of the turbulent fluctuations in the liquid. Specifically, directly above the bed the particles significantly enhance turbulence at the lower end of the Shields number range investigated.

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Effect of geometry on the mechanisms for off-bottom solids suspension in a stirred tank

Cited by 69 publications

References 17 publications

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

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

Single-Use Bioreactors for Animal and Human Cells

Simulations of granular bed erosion due to a mildly turbulent shear flow

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