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.

Mixing Enhancement of Non-Newtonian Fluids Using Unconventional Configurations

2002 ◽  
Author(s):  
Gabriel Ascanio ◽  
Magdalena Brito-Baza´n ◽  
Edmundo Brito-De La Fuente ◽  
Pierre J. Carreau ◽  
Philippe A. Tanguy
Keyword(s):  
Radial Flow ◽  
Mixing Time ◽  
Axial Flow ◽  
Statistical Design ◽  
Shear Thinning ◽  
Mixing Enhancement ◽  
Mixing Times ◽  
Operating Modes ◽  
Shear Thinning Fluids ◽  
Dynamic Perturbation

Dynamic perturbations and off-centered single impeller configurations have been investigated to reduce mixing time with shear thinning fluids. The use of a color-decolorization technique based on a fast acid-base reaction allowed to measure mixing times and to reveal the presence of both segregated and dead zones. A statistical design approach has been used to evaluate the effect of the impeller position as well as the dynamic conditions and their interactions. Mixing times and flow patterns for shear thinning fluids were presented and compared to conventional operating modes. Homogenization was significantly enhanced when a radial flow impeller was used under both off-centered and dynamic perturbation conditions. In the case of an axial flow impeller, a combination of a large axial displacement with long clockwise times and short counter-clockwise times gave better mixing times.

scholarly journals Ultrasonic velocity profiler applied to explore viscosity–pressure fields and their coupling in inelastic shear-thinning vortex streets

2021 ◽  
Vol 62 (9) ◽  
Author(s):  
Neetu Tiwari ◽  
Yuichi Murai
Keyword(s):  
Methyl Cellulose ◽  
Ultrasound Velocity ◽  
Shear Thinning ◽  
Working Fluid ◽  
Simultaneous Estimation ◽  
Measured Velocity ◽  
Pressure Poisson Equation ◽  
Shear Thinning Fluids ◽  
Pressure Fields ◽  
Inelastic Shear

Abstract A method for simultaneous estimation of viscosity and pressure fields in inelastic shear-thinning fluids is developed by means of ultrasound velocity profiling technique (UVP). In the method, equation of continuity, rheological model and pressure Poisson equation are incorporated as data processing sequences for measured velocity distributions. The proposed method is applied to study the vortex street structure formed behind a circular cylinder, which shows viscosity–pressure coupling due to shear-thinning property of fluid. For demonstration, aqueous solution of CMC (carboxy methyl cellulose) of weight concentration of 0.1% is chosen as the working fluid with shear-thinning property. An alternating staggered pattern of low-pressure spots is successfully reconstructed for zero-shear-based Reynolds number, Re = 50–300. We have found that increasing Re resulted in decrease in vortex shedding Strouhal number because of vortex sustainability supported by shear-thinning property. Graphical abstract

Comparative Bio-sorption of Cadmium and Nickel Ions from Aqueous Solution onto Fibers of Date Palm using Fluidized Bed Column

2019 ◽  
Vol 70 (5) ◽  
pp. 1507-1512
Author(s):  
Baker M. Abod ◽  
Ramy Mohamed Jebir Al-Alawy ◽  
Firas Hashim Kamar ◽  
Gheorghe Nechifor
Keyword(s):  
Aqueous Solution ◽  
Heavy Metal ◽  
Metal Ions ◽  
Fluidized Bed ◽  
Removal Efficiency ◽  
Heavy Metal Ions ◽  
Date Palm ◽  
Operating Conditions ◽  
Initial Concentration ◽  
Bed Height

The aim of this study is to use the dry fibers of date palm as low-cost biosorbent for the removal of Cd(II), and Ni(II) ions from aqueous solution by fluidized bed column. The effects of many operating conditions such as superficial velocity, static bed height, and initial concentration on the removal efficiency of metal ions were investigated. FTIR analyses clarified that hydroxyl, amine and carboxyl groups could be very effective for bio-sorption of these heavy metal ions. SEM images showed that dry fibers of date palm have a high porosity and that metal ions can be trapped and sorbed into pores. The results show that a bed height of 6 cm, velocity of 1.1Umf and initial concentration for each heavy metal ions of 50 mg/L are most feasible and give high removal efficiency. The fluidized bed reactor was modeled using ideal plug flow and this model was solved numerically by utilizing the MATLAB software for fitting the measured breakthrough results. The breakthrough curves for metal ions gave the order of bio-sorption capacity as follow: Cd(II)]Ni(II).

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