Power Consumption of a Rushton Turbine Mixing Viscous Newtonian and Shear-thinning Fluids: Comparison between Experimental and Numerical Results

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.

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Power consumption for stirring shear thinning fluids by two-blade impeller

Energy ◽

10.1016/j.energy.2012.11.016 ◽

2013 ◽

Vol 50 ◽

pp. 326-332 ◽

Cited By ~ 15

Author(s):

Houari Ameur ◽

Mohamed Bouzit

Keyword(s):

Power Consumption ◽

Shear Thinning ◽

Shear Thinning Fluids

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

Chemical Engineering Research and Design ◽

10.1016/j.cherd.2017.01.018 ◽

2017 ◽

Vol 119 ◽

pp. 171-182 ◽

Cited By ~ 17

Author(s):

Marti Cortada-Garcia ◽

Valentina Dore ◽

Luca Mazzei ◽

Panagiota Angeli

Keyword(s):

Power Consumption ◽

Shear Thinning ◽

Shear Thinning Fluids ◽

Viscous Shear

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

International Journal of Chemical Reactor Engineering ◽

10.1515/ijcre-2015-0200 ◽

2016 ◽

Vol 14 (5) ◽

pp. 1025-1033 ◽

Cited By ~ 10

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.

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