Effect of mixer geometry and operating conditions on flow mixing of shear thinning fluids with yield stress

AIChE Journal ◽  
2013 ◽  
Vol 60 (3) ◽  
pp. 1156-1167 ◽  
Author(s):  
Jaime Sossa-Echeverria ◽  
Fariborz Taghipour
Keyword(s):  
Yield Stress ◽  
Shear Thinning ◽  
Operating Conditions ◽  
Shear Thinning Fluids ◽  
Flow Mixing

New Chaotic Approach for Mixing Shear-Thinning Fluids in Stirred Tanks

2003 ◽  
Author(s):  
Gabriel Ascanio ◽  
Ste´phane Foucault ◽  
Philippe A. Tanguy
Keyword(s):  
Aqueous Solution ◽  
Shear Thinning ◽  
Operating Conditions ◽  
Mixing Times ◽  
Acid Base ◽  
Stirred Tanks ◽  
Shear Thinning Fluids ◽  
Standard Configuration ◽  
Inelastic Shear ◽  
In The Beginning

The mixing of inelastic shear-thinning fluids has been investigated by using a chaotic approach. Two different scenarios based on single and dual off-centered impellers have been proposed and compared to the standard configuration (steady stirring) showing the potentialities and drawbacks of the proposed arrangements. Mixing times were evaluated by means of color-discoloration technique based on a fast acid-base indicator reaction. An aqueous solution of low concentrated purple bromocresol was used as tracer and added to the tank in the beginning of the experiments and then NaOH or HCl were added to the fluid to be tested in order to change its pH and as a consequence its color. It is demonstrated that, if the operating conditions of the proposed scenarios are properly set, the mixing times can be drastically reduced compared to those obtained under the standard configuration.

scholarly journals Mixing of shear-thinning fluids with yield stress in stirred tanks

AIChE Journal ◽  
2006 ◽  
Vol 52 (7) ◽  
pp. 2310-2322 ◽  
Author(s):  
P. E. Arratia ◽  
J. Kukura ◽  
J. Lacombe ◽  
F. J. Muzzio
Keyword(s):  
Yield Stress ◽  
Shear Thinning ◽  
Stirred Tanks ◽  
Shear Thinning Fluids

Mixing of Shear Thinning Fluids in Cylindrical Tanks: Effect of the Impeller Blade Design and Operating Conditions

2016 ◽  
Vol 14 (5) ◽  
pp. 1025-1033 ◽  
Author(s):  
Houari Ameur
Keyword(s):  
Power Consumption ◽  
Mixing Time ◽  
Shear Thinning ◽  
Operating Conditions ◽  
Impeller Blade ◽  
Straight Blade ◽  
Shear Thinning Fluids ◽  
Cylindrical Tanks ◽  
The Impact ◽  
Rotational Direction

Abstract The 3D flow fields and power consumption within a cylindrical vessel stirred by a rotating turbine are numerically studied. Simulations are performed to determine the impact of changes in operating parameters on the mixing characteristics. Investigations are focused on effects of the impeller blade curvature, shaft speed and impeller rotational direction. The fluid simulated has a shear thinning behavior. Designing the blade in retreat shape seems very promising in term of power consumption since a reduction of Np is obtained with increasing blade curvature. In the positive rotational direction, the retreat bladed impeller yields highly radial flows with less power consumption than the straight bladed impeller. The 45° retreat blade gave an increase in the radial velocity by 39 %, compared with the straight blade. But, a better axial circulation is obtained with the straight blade. The comparison between the positive rotational direction (+w) and the negative rotational direction (–w) cases revealed that, a reduced mixing time can be obtained with a retreat bladed impeller operating in the negative rotational direction (–w), but with further power consumption.

scholarly journals Droplet splashing during the impact on liquid pools of shear-thinning fluids with yield stress

2021 ◽  
Vol 33 (11) ◽  
pp. 112106
Author(s):  
Xiaoyun Peng ◽  
Tianyou Wang ◽  
Kai Sun ◽  
Zhizhao Che
Keyword(s):  
Yield Stress ◽  
Shear Thinning ◽  
Shear Thinning Fluids ◽  
Liquid Pools ◽  
The Impact

scholarly journals Concentric cylinder viscometer flows of Herschel-Bulkley fluids

2019 ◽  
Vol 29 (1) ◽  
pp. 173-181 ◽  
Author(s):  
Hans Joakim Skadsem ◽  
Arild Saasen
Keyword(s):  
Shear Rate ◽  
Yield Stress ◽  
Couette Flow ◽  
Newtonian Fluid ◽  
Shear Thinning ◽  
Newtonian Fluids ◽  
Drilling Fluids ◽  
Concentric Cylinder ◽  
Shear Thinning Fluids ◽  
Cylinder Viscometer

Abstract Drilling fluids and well cements are example non-Newtonian fluids that are used for geothermal and petroleum well construction. Measurement of the non-Newtonian fluid viscosities are normally performed using a concentric cylinder Couette geometry, where one of the cylinders rotates at a controlled speed or under a controlled torque. In this paper we address Couette flow of yield stress shear thinning fluids in concentric cylinder geometries.We focus on typical oilfield viscometers and discuss effects of yield stress and shear thinning on fluid yielding at low viscometer rotational speeds and errors caused by the Newtonian shear rate assumption. We relate these errors to possible implications for typical wellbore flows.

The Flow and Decay Behavior of a Submerged Shear-Thinning Jet With Yield Stress

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Khaled J. Hammad
Keyword(s):  
Yield Stress ◽  
Numerical Solutions ◽  
Shear Thinning ◽  
Momentum Conservation ◽  
Recirculation Region ◽  
Centerline Velocity ◽  
Flow Recirculation ◽  
Shear Thinning Fluids ◽  
Submerged Jets ◽  
The Impact

The flow and decay characteristics of submerged jets of shear-thinning fluids with yield stress are studied. Numerical solutions to the governing mass and momentum conservation equations, along with the Herschel–Bulkley rheological model, are obtained using a finite-difference scheme. A parametric study is implemented to investigate the influence of flow inertia and rheology over the following range of parameters: Reynolds number, 50 ≤ Re ≤ 200; yield number, 0 ≤ Y ≤ 1; and shear-thinning index, 0.6 ≤ n ≤ 1. A large recirculation region exists for Newtonian and shear-thinning non-Newtonian jets. However, the extent and strength of the recirculation region substantially diminish with the yield number and, to a lesser extent, when the shear-thinning index is reduced from 1 to 0.6. Increasing the yield number beyond a critical value eliminates flow recirculation. The centerline velocity and momentum decay of shear-thinning jets with yield stress, in general, increase with the yield number. Velocity- and momentum-based depths of penetration, DPU, and DPM, respectively, are introduced and presented. DPU and DPM are the downstream locations corresponding to 90% decay in the initial centerline velocity and jet momentum, respectively. A substantial decrease in DPU and DPM is observed when the shear-thinning index is reduced from 1 to 0.6 for Y = 0. The presence of yield stress significantly reduces both DPU and DPM of submerged jets. The impact of shear-thinning on the decay characteristics of the jet is more pronounced at low yield numbers.

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