Taylor‐Couette unit with a lobed inner cylinder cross section

Abstract

A new mixing unit, based on a modification of the classical Taylor-Couette (TC) unit is proposed, where a lobed profile of the inner cylinder cross section is used. The shear rate distribution of the lobed Taylor-Couette (LTC) unit have been computed through computational fluid dynamic simulations and compared with those of the TC unit and a standard stirred tank (ST). It is found that since the flow pattern of the LTC units becomes temporal-periodic at each point with respect to the nonrotational outer cylinder, it reduces the formation of the low velocity gradient (low shear rate) region, typically generated in the vortex core of the TC units. The obtained distributions of the shear rate are substantially narrower than those of the TC and the ST units. Variation of the ratio between the maximum and the minimum gap widths can lead to significant changes in the shear rate distribution, and there exists an optimal range of such ratio, where the shear rate distribution is not only very narrow but also insensitive to the variation of the gap widths.

Effect of flow field heterogeneity in coagulators on aggregate size and structure

“…The rotation of the inner cylinder was considered by a rotating reference frame, by rotating the liquid adjacent to the inner cylinder wall at the same velocity as the latter, whereas the outer cylinder is treated as static. 61 As it was shown by several authors, 17,45,62 the Reynolds stress model combined with a standard wall function provides the best agreement of local mean velocity components obtained from CFD simulations with experimental data. Therefore, in this work, we confine to a macroscopic comparison of the measured and calculated net torque for TC-type devices.…”

“…Two types of outer cylinder were used in the experiments, one made from stainless steel with several sampling ports, and the other from precision glass Duran from Schott (Mainz, Germany) used for flow field visualization with rheoscopic fluid. More details about the geometry of the coagulation units as well as on the characterization of the flow field through CFD can be found in Soos et al 17 for the TC-type devices, and Waldner et al 14 and Soos et al 46 for the ST, respectively. Characterization of Flow Conditions and Flow Field Visualization.…”

“…However, in reality for a given stirring device, the shear rate exhibits a distinct distribution. [16][17][18][19][20][21][22][23][24][25] As the rate constants of both aggregation [26][27][28] and breakage 29 are not linearly dependent on shear rate, its volume average value cannot be used to properly characterize these processes, but the heterogeneity of the flow field needs to be considered. 30,31 Therefore, reducing the considerations on hGi can lead to erroneous results in the scale-up, and it complicates the comparison of different stirring/mixing devices.…”

Induction of mammalian cell death by simple shear and extensional flows

“…This increase was linearly dependent on the rate of energy dissipation in the capillary, independently of the flow regime (laminar or turbulent with 500 < Re < 6,000) and residence time. Due to the fact that industrial culture systems (small and large scale) are characterized by a heterogeneous environment (Soos et al, 2007) and often exhibit laminar regions (Lara et al, 2006;Zalc et al, 2001), the investigation of laminar shear flow on cell death is of practical importance to improve biopharmaceutical processes.…”

Effect of the rotor shape on the mixing characteristics of a continuous flow Taylor-vortex reactor

“…Suh (1976, 1979), for instance, used rotors with a v-grooved surface to enhance laminar mixing in highly viscous fluids. Homogenising and maximising shear rates were achieved by furnishing the rotor with a lobed cross-section (Soos et al, 2007). Shape modifications investigated include concave (Wiener et al, 1997) or undulating geometries (Drozdov, 2002) and conical rotors.…”