Which impeller should be chosen for efficient solid–liquid mixing in the laminar and transitional regime?

Abstract

The vast majority of solid–liquid mixing studies have focused on high Reynolds number applications with configurations and impeller geometries adapted to this type of regime. However, the mixing of particles in a viscous fluid is an essential element of many contemporary industries. We used the computational fluid dynamics‐discrete element method model previously developed in our group to investigate solid–liquid mixing with close‐clearance impellers in the laminar regime of operation. We compared different geometries, that is, the double helical ribbon, anchor, Paravisc™, and Maxblend™ impellers. We investigated the impact of fluid viscosity and compared the results with those obtained with the pitched blade turbine, a more commonly used impeller, based on power consumption for equivalent mixing states. This study highlights that the higher the viscosity of the fluid, the more interesting it is to use close‐clearance impellers for their ability to generate a strong shear stress and a strong bulk flow in the entire vessel.

Chirality enhanced shear‐free mixing of highly viscous fluids in an origami reactor

“…Reactors with long stretch distances produce a more significant deformation, which creates a stronger squeeze on the internal fluid and promotes mixing. The mixing performance of the chiral origami reactor was compared with the stirred tank reactor (STR), which has a propelled stirrer, an anchor stirrer, and a helical ribbon stirrer 43 (Figure S6a), respectively. A 50 cm 3 beaker was used as a stirred tank.…”

Physical limitations induced by a medium based on wheat bran for the production of biopesticides by Bacillus thuringiensis spp kurstaki

“…Pour les suspensions de son de blé, des mesures de viscosimétrie rotationnelle (Le et al, 2017) ont été effectuées avec un rhéomètre Mars III (Thermo Scientific, Karlsruhe, Allemagne, Cmin/max : 10 -8 /0,2 Nm, Nmin/max : 10 -7 /1500 rpm, logiciel Rheowin Job manager). Pour assurer une homogénéité de la suspension (mouvement axial et radial) lors des mesures, un agitateur en forme de ruban hélicoïdal (dHR=26 mm, hHR= 25,8 mm, lHR= 2 mm) et une cuve cylindrique (Dcuve= 27,2 mm, Hcuve= 72 mm) ont été utilisé (Eriksson et al, 2002), (Delacroix et al, 2021). Préalablement, la courbe de consommation de puissance (Np vs ReMixing) a été établie avec des fluides Newtoniens puis généralisée (concept de (Metzner & Otto, 1957)) avec des fluides rhéofluidifiants.…”

Large blade impeller application for turbulent liquid–liquid and solid–liquid mixing

“…Focusing on MB impellers, relatively recent investigations mainly based on computational methods reported good performances from the laminar to the turbulent regime, [ 5 ] the particular shape with a paddle at the bottom surmounted by a grid proved to be very effective for generating efficient mixing at a low‐power consumption as compared with other impellers, [ 6 ] effective solid suspension in viscous fluids was obtained with increasing advantages moving towards lower Reynolds numbers from transitional to laminar flows. [ 7 ] On the experimental side, mixing with MB impellers has been characterized by electrical resistance tomography (ERT) in the case of shear‐thinning fluid possessing yield stress [ 8 ] and solid–liquid suspensions. [ 9 ] Also, power consumption, [ 10 ] global pumping characteristics, [ 11 ] and mixing time [ 12 ] have been obtained experimentally, mainly with non‐Newtonian fluids.…”