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The hydrotransport of settling particles using laminar flow as opposed to the more energy‐ and water‐intensive turbulent flow has remained a tentative option for industries due to the complexity in characterizing particle settling dynamics in opaque non‐Newtonian fluids under sheared conditions. To provide insight into this unknown physics, this study focused on viscoelastic shear‐thinning fluids and developed a semi‐empirical model to characterize the batch‐settling dynamics of dilute suspensions (<5 vol% solids concentration) experiencing a shear field. These suspensions consisted of spherical glass microparticles in aqueous xanthan gum solutions. Settling profiles were measured with Electrical Resistance Tomography (ERT) while a motorized belt generated a cross‐shear field. The data acquired by the ERT showed that introducing cross‐shear fields into such suspensions increased settling rates when compared with static settling contexts. Then, a semi‐empirical model describing the "acceleration phase" of the settling process was developed and validated at accuracies between 81% and 97%. [ABSTRACT FROM AUTHOR]

Accelerated growth of scale was studied in a baffled agitated reactor, which could be disassembled into nine sections, allowing quantitative determination of scale thickness. A coordinate measuring machine was used to determine the scale thickness on individual wall segments. The growth pattern of the scale was found to be nonuniform due to the variation of fluid velocity near the wall at various heights. Computational fluid dynamics (CFD) simulation showed that fluid flow is time‐dependent and has two distinct flow zones, one involving recirculation through the impeller in the lower part of the vessel and the other involving lower velocities due to the flow separation at the wall in the upper part. CFD simulation also showed the presence of macroinstabilities, which manifest as asymmetrical and chaotic flow structures with relatively long‐time scales. Scale growth is found to be prominent in regions where the fluid velocity and wall shear stresses are low. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3912–3922, 2018 [ABSTRACT FROM AUTHOR]

Abstract: Computational fluid dynamics (CFD) models were employed to investigate flow conditions inside a model reactor in which yield stress non‐Newtonian liquid is mobilized using submerged recirculating jets. The simulation results agree well with the experimental results of active volume in the reactor obtained using flow visualization by the authors in a previous study. The models developed are capable of predicting a critical jet velocity (vc) that determines the extent of active volume obtained due to jet mixing. The vc values are influenced both by the rheological properties of the liquid and the nozzle orientation. The liquid with higher effective viscosity leads to higher vc for a downward facing injection nozzle. However, an upward facing injection nozzle along with a downward facing suction nozzle generates enhanced complementary flow fields which overcome the rheological constraints of the liquid and lead to lower vc. [ABSTRACT FROM AUTHOR]

We provide experimental demonstration that the spread of tracer elements in a tank containing a viscoelastic liquid and agitated by a submerged jet pointing to the base of the tank can be influenced by the relaxation time of the liquid. We analyzed the temporal spreading of the boundary of a tracer-front in two dimensions using flow visualization at early stages and found that for a given fluid, the evolution of the tracer-front at various injection velocities follows a universal trajectory when considered on a normalized time scale of [ABSTRACT FROM AUTHOR]

The article discusses research on the effects of impeller type and baffling arrangement on impeller power consumption. It provides information on specific impeller power required for solid suspensions at extremely high solid concentrations also known as ultra-high solids concentration. It discusses a method used in simulating the presence of impurities in the liquid phase and its influence on liquid viscosity.

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The article discusses a study which investigated the effect of montmorillonite clay on the biodegradation of oxo-biodegradable polyethylene. The study carried out initial abiotic oxidation corresponding to about four years of composting as thermo-oxidation at composting temperatures. Environmental scanning electron microscopy was also used to monitor the growth of bacteria on the surface of the polymer. Details of the findings are discussed.

The effects of impeller type, Newtonian shear thinning liquid viscosities, and noncoalescing conditions on the impeller gas cavities, impeller power consumption, and Sauter mean bubble diameter (d32) in a multiphase agitated vessel were systematically studied. An underwater recording technique was used to study gas cavities and bubble size in various operating and design conditions. The gas cavity images were used to relate d32 to gas cavity structure. It was observed that d32 values increase with an increase in Newtonian and shear thinning liquid viscosities. Results also indicate that impellers operating in shear thinning liquids consume higher gassed power at the same operating conditions compared with those in Newtonian fluids. In addition, the d32 values in noncoalescing liquids are substantially smaller compared with those in coalescing solutions at the same Pg/V. Mathematical correlations are proposed for estimating the d32 in the impeller discharge stream and Pg/V in viscous Newtonian and non‐Newtonian solutions. [ABSTRACT FROM AUTHOR]