scholarly journals CFD Investigation Of Mixing Of Yield-Pseudoplastic Fluid With Anchor Impeller

2021 ◽  
Author(s):  
Poonam Prajapati
Keyword(s):  
Power Consumption ◽  
Mixing Time ◽  
Diameter Ratio ◽  
Cfd Modeling ◽  
Cylindrical Tank ◽  
Flat Bottom ◽  
Pseudoplastic Fluid ◽  
Impeller Blade ◽  
Blade Width ◽  
Fluid Rheology

The Anchor impeller, which is a close clearance impeller, produces high shear near the vessel wall and is recommended for mixing of highly viscous fluids. A thorough search of the literature suggests that few publications have beeen devoted to the computational fluid dynamics (CFD) modeling of mixing of non-Newtonian fluids with the anchor impeller. Thus the objectives of this study are (i)to generate a 3-D flow field for mixing of yield-pseudoplastic fluid in a flat bottom cylindrical tank equipped with two-and four-blade anchor impellers using CFD modeling technique, (ii) to evaluate the effects of fluid rheology agitator speed, number of blades, vessel clearance and impeller blade width on power consumption, mixing time and flow patterns, and (iii) to determine the optimum value of clearance to diameter ratio and impeller blade width to diameter ratio on the basis of minimum mixing time. The study was carried out for a yield-stress pseudoplastic fluid, using a CFD package (Fluent), to simulate the 3-D flow domain generated in a cylindrical tank equipped with two-and four-blade anchor impellers. The multiple reference frame (MRF) technique was employed to model the rotation of impellers. The rheology of the fluid was approximated using the Herschel-Bulkley model. To validate the model, CFD results for the power were compared to experimental data. After the flow fields were calculated, the simulations for tracer homogenization was performed to simulate the mixing time. The effect of impeller speed, fluid rheology, and number of impellers on power consumption, mixing time, and flow pattern were explored. The optimum values of c/D (clearance to diameter) and w/D (impeller blade width to diameter) ratios were determined on the basis of minimum mixing time.

scholarly journals CFD Investigation Of Mixing Of Yield-Pseudoplastic Fluid With Anchor Impeller

2021 ◽  
Author(s):  
Poonam Prajapati
Keyword(s):  
Power Consumption ◽  
Mixing Time ◽  
Diameter Ratio ◽  
Cfd Modeling ◽  
Cylindrical Tank ◽  
Flat Bottom ◽  
Pseudoplastic Fluid ◽  
Impeller Blade ◽  
Blade Width ◽  
Fluid Rheology

The Anchor impeller, which is a close clearance impeller, produces high shear near the vessel wall and is recommended for mixing of highly viscous fluids. A thorough search of the literature suggests that few publications have beeen devoted to the computational fluid dynamics (CFD) modeling of mixing of non-Newtonian fluids with the anchor impeller. Thus the objectives of this study are (i)to generate a 3-D flow field for mixing of yield-pseudoplastic fluid in a flat bottom cylindrical tank equipped with two-and four-blade anchor impellers using CFD modeling technique, (ii) to evaluate the effects of fluid rheology agitator speed, number of blades, vessel clearance and impeller blade width on power consumption, mixing time and flow patterns, and (iii) to determine the optimum value of clearance to diameter ratio and impeller blade width to diameter ratio on the basis of minimum mixing time. The study was carried out for a yield-stress pseudoplastic fluid, using a CFD package (Fluent), to simulate the 3-D flow domain generated in a cylindrical tank equipped with two-and four-blade anchor impellers. The multiple reference frame (MRF) technique was employed to model the rotation of impellers. The rheology of the fluid was approximated using the Herschel-Bulkley model. To validate the model, CFD results for the power were compared to experimental data. After the flow fields were calculated, the simulations for tracer homogenization was performed to simulate the mixing time. The effect of impeller speed, fluid rheology, and number of impellers on power consumption, mixing time, and flow pattern were explored. The optimum values of c/D (clearance to diameter) and w/D (impeller blade width to diameter) ratios were determined on the basis of minimum mixing time.

scholarly journals Investigation of the Performance of V-cut Turbines for Stirring Shear-thinning Fluids in a Cylindrical Vessel

2020 ◽  
Vol 64 (3) ◽  
pp. 207-211
Author(s):  
Houari Ameur
Keyword(s):  
Power Consumption ◽  
Mixing Time ◽  
Shear Thinning ◽  
New Technique ◽  
Flow Conditions ◽  
Impeller Blade ◽  
Pumping Rate ◽  
Shear Thinning Fluids ◽  
Discharge Flow Rate ◽  
A New Technique

The impeller design is the most crucial parameter to enhance the performance of stirred tanks. The cut in the impeller blade is a new technique to save the energy of impellers in mixing vessels without increasing the mixing time or reducing the product quality. In this paper, the new technique of cut is applied for a disc turbine rotating in an unbaffled cylindrical tank. Effects of the V-cut shape are highlighted. Non-Newtonian shear-thinning fluids are considered for the three flow regimes (laminar, transient, and turbulent). Effects of the number of blades on the flow patterns, pumping rate (Nq) and power consumption (Np) are explored. From the obtained results, a recirculation loop of flow is observed at the tip of each blade for impellers with less than three blades. These recirculation loops disappear with the increased number of blades. Under laminar flow conditions, the obtained results also revealed a decrease in power consumption and an increase in the discharge flow rate with the rise of Reynolds number. However, almost any changes were observed for these parameters (Np and Nq) under turbulent flow conditions.

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.

Hydrodynamics in a vessel stirred by simple and double helical ribbon impellers

2013 ◽  
Vol 3 (1) ◽  
Author(s):  
Houari Ameur ◽  
Mohamed Bouzit ◽  
Abdellah Ghenaim
Keyword(s):  
Power Consumption ◽  
Finite Volume Method ◽  
Satisfactory Agreement ◽  
Rotational Speed ◽  
Flat Bottom ◽  
Helical Ribbon ◽  
Shear Thinning Fluids ◽  
Tank Bottom ◽  
Volume Method ◽  
Fluid Rheology

AbstractThe present paper treats the agitation of shear thinning fluids in a cylindrical unbaffled vessel with a flat-bottom. Two kinds of impellers have been used: simple and double helical ribbons. This work is achieved with the help of CFD package (CFX-12.0), which is based on the finite volume method to solve the continuity and momentum equations. The effect of impeller rotational speed, fluid rheology, impeller size, impeller clearance from the tank bottom on the flow fields and power consumption have been investigated. Finally, a comparison between the two impellers is made. It was found that the best performance is obtained with double helical ribbon impeller placed at the middle of the tank, with moderate blade size and operating at Re g > 20. Our results have been compared with those of other literatures and a satisfactory agreement is observed.

scholarly journals CFD modeling of particle settling in drilling fluids: Impact of fluid rheology and particle characteristics

2021 ◽  
Vol 199 ◽  
pp. 108326
Author(s):  
Abdelrahman M. Awad ◽  
Ibnelwaleed A. Hussein ◽  
Mustafa S. Nasser ◽  
Hamidreza Karami ◽  
Ramadan Ahmed
Keyword(s):  
Cfd Modeling ◽  
Drilling Fluids ◽  
Particle Settling ◽  
Particle Characteristics ◽  
Fluid Rheology

Fluid Pressures on Unanchored Rigid Flat-Bottom Cylindrical Tanks Under Action of Uplifting Acceleration

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Tomoyo Taniguchi ◽  
Yoshinori Ando
Keyword(s):  
Velocity Potential ◽  
Fluid Velocity ◽  
Fluid Pressure ◽  
Angular Acceleration ◽  
Bottom Plate ◽  
Center Line ◽  
Cylindrical Tank ◽  
Cylindrical Coordinates ◽  
Flat Bottom ◽  
Cylindrical Tanks

To protect flat-bottom cylindrical tanks against severe damage from uplift motion, accurate evaluation of accompanying fluid pressures is indispensable. This paper presents a mathematical solution for evaluating the fluid pressure on a rigid flat-bottom cylindrical tank in the same manner as the procedure outlined and discussed previously by the authors (Taniguchi, T., and Ando, Y., 2010, “Fluid Pressures on Unanchored Rigid Rectangular Tanks Under Action of Uplifting Acceleration,” ASME J. Pressure Vessel Technol., 132(1), p. 011801). With perfect fluid and velocity potential assumed, the Laplace equation in cylindrical coordinates gives a continuity equation, while fluid velocity imparted by the displacement (and its time derivatives) of the shell and bottom plate of the tank defines boundary conditions. The velocity potential is solved with the Fourier–Bessel expansion, and its derivative, with respect to time, gives the fluid pressure at an arbitrary point inside the tank. In practice, designers have to calculate the fluid pressure on the tank whose perimeter of the bottom plate lifts off the ground like a crescent in plan view. However, the asymmetric boundary condition given by the fluid velocity imparted by the deformation of the crescent-like uplift region at the bottom cannot be expressed properly in cylindrical coordinates. This paper examines applicability of a slice model, which is a rigid rectangular tank with a unit depth vertically sliced out of a rigid flat-bottom cylindrical tank with a certain deviation from (in parallel to) the center line of the tank. A mathematical solution for evaluating the fluid pressure on a rigid flat-bottom cylindrical tank accompanying the angular acceleration acting on the pivoting bottom edge of the tank is given by an explicit function of a dimensional variable of the tank, but with Fourier series. It well converges with a few first terms of the Fourier series and accurately calculates the values of the fluid pressure on the tank. In addition, the slice model approximates well the values of the fluid pressure on the shell of a rigid flat-bottom cylindrical tank for any points deviated from the center line. For the designers’ convenience, diagrams that depict the fluid pressures normalized by the maximum tangential acceleration given by the product of the angular acceleration and diagonals of the tank are also presented. The proposed mathematical and graphical methods are cost effective and aid in the design of the flat-bottom cylindrical tanks that allow the uplifting of the bottom plate.

Characteristics of Power Consumption and Mixing Time of New Large Paddle (HB Type) Impeller

2015 ◽  
Vol 41 (5) ◽  
pp. 276-280 ◽  
Author(s):  
Yoshihito Kato ◽  
Shota Ohtani ◽  
Haruki Furukawa
Keyword(s):  
Power Consumption ◽  
Mixing Time

Differences in Mixing Power Consumption between Dished-Bottom and Flat-Bottom Vessels

2010 ◽  
Vol 36 (1) ◽  
pp. 25-29 ◽  
Author(s):  
Yoshihito Kato ◽  
Yutaka Tada ◽  
Kunihiko Urano ◽  
Azusa Nakaoka ◽  
Yuichiro Nagatsu
Keyword(s):  
Power Consumption ◽  
Flat Bottom

Comments on "Experimental Studies and CFD Modeling on the Effects of a Cut in the Baffle on Power Consumption"

2009 ◽  
Vol 4 (1) ◽  
Author(s):  
Ivan Fort
Keyword(s):  
Power Consumption ◽  
Cfd Simulation ◽  
Experimental Studies ◽  
Power Input ◽  
Cfd Modeling ◽  
Turbulent Regime

Critical comments on results of the CFD simulation of the impeller power input in a cylindrical baffled vessel under turbulent regime of flow of agitated liquid.

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