CFD Analysis and Design Optimization in a Curved Blade Impeller

2017 ◽  
Vol 15 (1) ◽  
Author(s):  
Nazila Sutudehnezhad ◽  
Ramin Zadghaffari
Keyword(s):  
Flow Field ◽  
Mixing Time ◽  
Computational Method ◽  
Stirred Tank ◽  
Mixing Efficiency ◽  
Rushton Turbine ◽  
Stirred Tank Reactors ◽  
Analysis And Design ◽  
Curved Blade ◽  
Reported Data

Abstract Mixing efficiency in stirred tank reactors is an important challenge in the design of many industrial processes. The effect of blade shape on mixing efficiency has been studied in the present work. The computational method has been used to investigate the flow field, power consumption, pumping capacity, hydraulic efficiency, and mixing time in a fully baffled tank stirred by a Rushton turbine and different curved blade impellers. Flow in a stirred tank reactor involves interactions between flow around rotating blades and stationary baffles. The flow field was developed using the sliding mesh (SM) approach in computational fluid dynamics (CFD). The realizable k-ε was used to model the turbulence. A reasonable agreement between the experimental reported data and simulation results indicated the validity of CFD model. It has been revealed that increasing the blade curvature, at approximately the same mixing time would enhance the mixing efficiency up to 61.3 % in comparison with the Rushton turbine. This mixing efficiency would favor the employment of curved blade impellers due to the cost-benefits of stirred tank operations.

scholarly journals CFD simulation of the hydrodynamics and mixing time in a stirred tank

2010 ◽  
Vol 16 (4) ◽  
pp. 379-386 ◽  
Author(s):  
Aoyi Ochieng ◽  
Maurice Onyango
Keyword(s):  
Cfd Simulation ◽  
Draft Tube ◽  
Mixing Time ◽  
Operating Cost ◽  
Flow Fields ◽  
Stirred Tank ◽  
Mixing Efficiency ◽  
Phase System ◽  
Rushton Turbine ◽  
Power Draw

Hydrodynamics and mixing efficiency in stirred tanks influence power draw and are therefore important for the design of many industrial processes. In the present study, both experimental and simulation methods were employed to determine the flow fields in different mixing tank configurations in single phase system. The laser Doppler velocimetry (LDV) and computational fluid dynamics (CFD) techniques were used to determine the flow fields in systems with and without a draft tube. There was a reasonable agreement between the simulation and experimental results. It was shown that the use of a draft tube with the Rushton turbine and hydrofoil impeller resulted in a reduction in the homogenization energy by 19.2% and 17.7%, respectively. This indicates that a reduction in the operating cost can be achieved with the use of a draft tube in a stirred tank and there would be a greater cost reduction in a system stirred by the Rushton turbine compared to that stirred by a propeller.

An Effect of Fractal Baffles and Impellers with Double Stage 4-Blade Rushton Turbine to Fluid Flow Behaviour in Stirred Tank

2014 ◽  
Vol 660 ◽  
pp. 816-822 ◽  
Author(s):  
Bukhari Manshoor ◽  
Afifah Yusof ◽  
Suraya Laily ◽  
Izzuddin Zaman ◽  
Amir Khalid
Keyword(s):  
Flow Field ◽  
High Velocity ◽  
Velocity Vector ◽  
Fluid Mixing ◽  
Stirred Tank ◽  
Mixing Efficiency ◽  
Rushton Turbine ◽  
Fractal Pattern ◽  
Piv Technique ◽  
Piv Measurement

The stirred tank is widely used in many industries to obtain the desired type of fluid mixing. In the context of mixing process, two different fluids and have a different properties will mix in a single equipment to produce another fluid with a new property. In this research, a new approach of stirred tank which is containing a new design of baffles and impellers was proposed for fluid mixing. The new design of baffles and impellers that proposed here are used a fractal pattern for both parts in the stirred tank. Implementing a fractal pattern for baffles and impellers in stirred tank believe will influence the flow characteristic inside the stirred tank, hence will improve a mixing performance. In order to investigate the kinds of flow properties, a Particle Image Velocimetry (PIV) technique with 1 μm seeding particle was used. Four configurations were tested which are normal baffles and normal impellers, normal baffles and fractal impellers, fractal baffles and normal impellers, and the last configuration is fractal baffles and fractal impellers. In this study, dual Rushton impellers with 4 blades were used with the configurations mentioned. The result shows the significant flow field capture by PIV measurement on each configuration. By using fractal impeller some vortex are shown in the tank and high velocity vector on flow field compare with normal impeller while normal baffles gives high velocity vector depends on the configuration were used. From the results, it was showed that the fractal design can give a certain level of mixing efficiency in stirred tank. The PIV technique also gives good flow visualization in order to determine the flow pattern in stirred tank with a new concept of baffles and impellers.

scholarly journals Novel Evaluation Method to Determine the Local Mixing Time Distribution in Stirred Tank Reactors

2021 ◽  
pp. 100098
Author(s):  
J. Fitschen ◽  
S. Hofmann ◽  
J. Wutz ◽  
A.v. Kameke ◽  
M. Hoffmann ◽  
...  
Keyword(s):  
Time Distribution ◽  
Evaluation Method ◽  
Mixing Time ◽  
Stirred Tank ◽  
Stirred Tank Reactors

scholarly journals Comparative analysis of mixing efficiency and distribution induced by radial impellers in bioreactors with stirred bed of immobilized cells

2010 ◽  
Vol 16 (1) ◽  
pp. 47-64
Author(s):  
Anca-Irina Galaction ◽  
Anca-Marcela Lupăşteanu ◽  
Marius Turnea ◽  
Dan Caşcaval
Keyword(s):  
Experimental Data ◽  
Comparative Analysis ◽  
Immobilized Cells ◽  
Mixing Time ◽  
Mixing Efficiency ◽  
Rushton Turbine ◽  
Mobile Bed ◽  
Main Factors ◽  
Good Concordance

The influences of the main factors on the mixing efficiency and distribution for a bioreactor with stirred/mobile bed of immobilized S. cerevisiae cells in alginate (biocatalyst particles with 4, 4.6 and 5.2 mm diameters) have been comparatively analyzed for six radial impellers: a disperser sawtooth, Smith turbine, a pumper mixer, a curved bladed turbine, a paddle with six blades, a pitched bladed turbine vs. Rushton turbine. The most efficient impellers, from the viewpoint of intensity and uniformity of the suspension circulation were found to be the Smith turbine, the paddle with six blades and the pitched bladed turbine. The mathematical correlations describing the influence of the main factors on mixing time were established for each studied impeller offering a good concordance with the experimental data (the average deviations vary from ?7.9% for pitched bladed turbine to ?12.1% for disperser sawtooth).

Experimental Investigation of the Use of Synthetic Jets for Mixing in Vessels

2011 ◽  
Vol 133 (9) ◽  
Author(s):  
Mushtak Al-Atabi
Keyword(s):  
Mixing Time ◽  
Synthetic Jets ◽  
Stirred Tank ◽  
Fluid Viscosity ◽  
Stirred Tank Reactors ◽  
Mixing Performance ◽  
Shear Rates ◽  
Local Shear ◽  
Continuously Stirred Tank Reactor ◽  
Visualization Techniques

Mixing is an important process in various industries. Different designs have been suggested in order to reduce the local shear rates in mechanically stirred mixing vessels, also known as continuously stirred tank reactors, in order to account for the mixing requirements for sensitive materials such as biological materials and biofluids where the high shear rate may damage the sensitive materials. This paper reports on the development of a continuously stirred tank reactor that can be used to achieve a variety of mixing assignments. This mixing is achieved using synthetic jets. The mixing performance was assessed using flow visualization techniques. The effects of fluid viscosity on mixing time were investigated. The results are very encouraging and are suggestive that the use of synthetic jets in mixing is a viable alternative to the conventional methods of mixing in vessels.

scholarly journals Optimization of the mixing in stirred bioreactors, 1. Comparative analysis of the mixing efficiency with different radial impellers for simulated broths

2007 ◽  
Vol 13 (1) ◽  
pp. 1-20 ◽  
Author(s):  
Dan Cascaval ◽  
Anca-Irina Galaction ◽  
Elena Folescu
Keyword(s):  
Mixing Time ◽  
Ph Sensor ◽  
Mixing Efficiency ◽  
Energetic Efficiency ◽  
Rushton Turbine ◽  
Stirred Bioreactor ◽  
Mixing Intensity ◽  
Bulk Volume ◽  
Shear Effects ◽  
Stirred Bioreactors

Although radial impellers, especially the Rushton turbine, are widely used in stirred bioreactors, their applicability is limited by the high apparent viscosities of the broth. Beside the intensification of broth circulation, the energetic efficiency and the shear effects on biocatalysts must be taken into account to select the optimum impeller or impellers combination. In this context, the paper presents a comparative study on the efficiency of seven different radial impellers for simulated broth mixing in a stirred bioreactor. The analysis was made by means of the mixing time values obtained by vertically changing the position of the pH-sensor in the broths, in correlation with the energy consumption needed for a certain level of mixing time or for the uniform distribution of the mixing intensity into the bulk volume of the broths.

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