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.

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 Experimental and CFD studies of power consumption in the agitation of highly viscous shear thinning fluids

2017 ◽  
Vol 119 ◽  
pp. 171-182 ◽  
Author(s):  
Marti Cortada-Garcia ◽  
Valentina Dore ◽  
Luca Mazzei ◽  
Panagiota Angeli
Keyword(s):  
Power Consumption ◽  
Shear Thinning ◽  
Shear Thinning Fluids ◽  
Viscous Shear

scholarly journals Power consumption for mixing of shear-thinning fluids

2021 ◽  
Vol 66 (2) ◽  
pp. 247-254
Author(s):  
Adina Ghirişan Miclăuş ◽  
◽  
Vasile Miclăuş ◽  
◽  
Keyword(s):  
Power Consumption ◽  
Shear Thinning ◽  
Shear Thinning Fluids
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