Hydrodynamic Performance of a Ring‐Style High‐Shear Impeller in Newtonian and Shear‐Thinning Fluids

Abstract

Laminar mixing of Newtonian and shear-thinning fluids induced by a Hockmeyer-type impeller was investigated. Two unbaffled tanks at three impellers off-bottom clearances (c) were studied. Six geometric combinations, i.e., two d/T and three c/T, were examined where d and T are the impeller and tank diameters, respectively. Determination of the Metzner-Otto constant (K s) was undertaken. The effects of d/T, c/T, and fluid rheology on K s , power demand, pumping, shear and viscous dissipation were analyzed. The evaluated geometric ratios and rheology do not significantly affect K s and power demand, only the rheology had an impact on the remaining hydrodynamic parameters. Pumping was favored with the Newtonian fluid, and shear and viscous dissipation increased with the shearthinning fluid.

The transition to aeration in turbulent two-phase mixing in stirred vessels

“…A few studies have covered the underlying mixing dynamics within an unbaffled stirred vessel (Busciglio, Grisafi, Scargiali, & Brucato, 2014). Some of them are devoted to the laminar regime (Guadarrama-Pérez et al, 2020;Lamberto, Alvarez, & Muzzio, 1999) and a few more deal with the turbulence regime (Glover & Fitzpatrick, 2007;Li, Wang, Feng, & Gu, 2017;Li, Xiang, & Xiang, 2020;Martínez-de Jesús, Ramírez-Muñoz, García-Cortés, & Cota, 2018). For instance, Li et al (2017) coupled a volume-of-fluid method to a Reynolds stress model to capture the gas-liquid interface and turbulent flow agitated by pitched blade turbines where the interface deflection reached the impeller hub.…”

Power Consumption and Fluid Mixing in a Scale-Down Geometry of a Stirred Digester for Biogas Production

“…Lower values have been suggested for mixed flow impellers, − and 3 times higher values have been recently obtained in the transitional regime from 2D-PIV data in a baffled vessel stirred by a pitched blade turbine . A value close to 12 was also obtained in an unbaffled vessel stirred with a high shear impeller …”

“…29 A value close to 12 was also obtained in an unbaffled vessel stirred with a high shear impeller. 30 The viscosity curves of the three solutions at 18 °C are reported as a function of the shear rate in Figure 3. Given the uncertainties in the value of K, the range of shear rates calculated by eq 4 adopting three different values of K (K = 11 and 11 ± 10%) at the three values of N adopted in the PIV experiments are marked with red rectangles.…”

CFD simulations of early- to fully-turbulent conditions in unbaffled and baffled vessels stirred by a Rushton turbine

“…Only a few applications of CFD to unbaffled stirred tanks are available in the literature (Trad et al, 2017;Li et al, 2017;Martínez-de Jesús et al, 2018;Li et al, 2020). Some of them are specifically devoted to the laminar regime where unbaffled tanks are largely used (Lamberto et al, 1999;Márquez-Baños et al, 2019;Guadarrama-Pérez et al, 2020), especially when non-Newtonian fluids are employed (Márquez-Baños et al, 2019;Guadarrama-Pérez et al, 2020). Others deal also with the turbulent regime (Glover and Fitzpatrick, 2007;Davoody et al, 2019).…”