CFD Study on the Flow Field and Power Characteristics in a Rushton Turbine Stirred Tank in Laminar Regime

2019 ◽  
Vol 17 (11) ◽  
Author(s):  
Li Liangchao ◽  
Chen Ning ◽  
Xiang Kefeng ◽  
Xiang Beiping
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Flow Pattern ◽  
Scale Up ◽  
Stirred Tank ◽  
Turbulent Regime ◽  
Laminar Regime ◽  
Power Number ◽  
Rushton Turbine ◽  
Working Medium

Abstract A computational fluid dynamics (CFD) simulation was performed to study the hydrodynamics characteristics in a Rushton turbine stirred tank in laminar regime. The effects of operating condition, working medium and geometrical parameter on the flow field and power number characteristics were investigated. It is found that the two-loop flow pattern is formed in laminar regime when the impeller is not very close to tank bottom, while its shape and size vary with Reynolds number and impeller diameter. For a given geometrical configuration, the flow pattern, power number and dimensionless velocity profile are mainly depended on Reynolds number, and do not change with working medium and scale-up for a constant Reynolds number. When impeller off-bottom clearance is too low and Reynolds number is relatively high, the fluid flow would transit from two-loop flow pattern to sing-loop flow pattern as that occurs in turbulent regime. Power number falls for larger impeller in laminar regime. Surprisingly, in laminar regime, power number in the baffled tank with small impeller is almost identical to that in the unbaffled tank.

Study of Flow Characteristics of Oil and Water in the Process of Stirring

2013 ◽  
Vol 353-356 ◽  
pp. 3190-3193
Author(s):  
Zong Rui Hao ◽  
Juan Xu ◽  
Hai Yan Bie ◽  
Zhong Hai Zhou
Keyword(s):  
Flow Field ◽  
Flow Pattern ◽  
Cross Section ◽  
Radial Flow ◽  
Flow Characteristics ◽  
Stirred Tank ◽  
Turbulent Model ◽  
Vof Model ◽  
Circular Flows ◽  
Oil Water

To study the flow pattern in the process of oil-water stirring in three paddle stirring tank, RNG k-ε turbulent model and VOF model are adopted to simulate the flow field at different time in the stirred tank with the baffle. The results showed that, in the stirring process, inverted cone manifold was formed in the center of the stirring shaft. The stratified area was formed in the baffle and gradually transported to the bottom of the tank. The two circular flows were formed among three groups of blades. And the axially acting of the fluid was strong, which made homogeneous stirring in the stirred tank. At the same time the radial flow of the cross-section inside the tank increased because of the baffle.

Transport phenomena in an agitated vessel with an eccentrically located impeller

2011 ◽  
Vol 65 (2) ◽  
Author(s):  
Magdalena Cudak ◽  
Joanna Karcz ◽  
Anna Kiełbus-Rąpała
Keyword(s):  
Reynolds Number ◽  
Shear Rate ◽  
Friction Coefficient ◽  
Transport Phenomena ◽  
Turbulent Regime ◽  
Cylindrical Wall ◽  
Flow Measurements ◽  
Rushton Turbine ◽  
Agitated Vessel ◽  
Inner Diameter

AbstractThe paper presents results of an experimental analysis of the transport phenomena at the vicinity of the wall of an unbaffled agitated vessel with an eccentrically located impeller. Distributions of the transport coefficients were experimentally studied using an electrochemical method within the turbulent regime of the Newtonian liquid flow. Measurements were carried out in an agitated vessel with the inner diameter T = 0.3 m. Liquid height in the vessel was equal to the inner diameter, H = T. The agitated vessel was equipped with a Rushton or a Smith turbine or an A 315 impeller. Eccentricity of the impeller shaft was varied from 0 to 0.53. Local values of the dimensionless shear rate, shear stress, dynamic velocity and friction coefficient were integrated numerically for the whole surface area of the cylindrical wall of the vessel. Averaged values of these quantities were correlated with the impeller eccentricity and modified Reynolds number. The proposed Eqs. (5)–(8), with the coefficients given in Table 2, have no equivalent in open literature concerning this subject. Distributions of the shear rate, γ/n, and friction coefficient, f, at the vicinity of the cylindrical wall of the unbaffled vessel equipped with eccentric Rushton or Smith turbine or A 315 impeller are very uneven and they depend significantly on the impeller eccentricity, e/R. Maximum local values of these variables are located on the wall section closest to the impeller blades. From among the tested impellers, the greatest effects of the impeller eccentricity, e/R, and the liquid turbulence (described by the modified Reynolds number Re P,M) on the averaged dimensionless shear rate (γ/n)m and friction coefficient, f m, are found for the radial-flow Rushton turbine located eccentrically in an unbaffled agitated vessel.

A Study on the Flow Patterns of a Second Grade Viscoe-Lastic Fluid Past a Cavity in a Horizontal Channel

2012 ◽  
Vol 29 (2) ◽  
pp. 207-215 ◽  
Author(s):  
C. H. Hsu ◽  
S. Y. Hu ◽  
K. Y. Kung ◽  
C. C. Kuo ◽  
C. C. Chang
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Flow Field ◽  
Flow Pattern ◽  
Newtonian Fluid ◽  
Viscoelastic Fluids ◽  
Flow Patterns ◽  
Horizontal Channel ◽  
Second Grade ◽  
Fluid Elasticity

AbstractThis paper studies the behavior of second grade viscoelastic fluid past a cavity in a horizontal channel. The effects of Reynolds number, fluid elasticity and the aspect ratio of the cavity on the flow field are simulated numerically. The equations are converted into the vorticity and stream function equations. The solution is obtained by the finite difference method.The behavior of viscoelastic fluids is quite different from the Newtonian fluid, due to the effects of fluid elasticity. Only one flow pattern appears when the Newtonian fluid past the cavity. However, three kinds of flow patterns appear while the viscoelastic fluids past the cavity by increasing Reynolds number from 20 to 300. The flow field is affected by the fluid elasticity as well as the aspect ratio of the cavity. The transitional flow pattern appears at lower Reynolds number as the higher elasticity fluid past the cavity with larger aspect ratio.

Considerations for ISO 9300: The Effects of Roughness and Form on the Discharge Coefficient of Toroidal-Throat Sonic Nozzles

2003 ◽  
Author(s):  
Jeff Gibson ◽  
David Stewart ◽  
Neil Barton
Keyword(s):  
Reynolds Number ◽  
Discharge Coefficient ◽  
Computational Techniques ◽  
Published Data ◽  
Turbulent Regime ◽  
Laminar Regime ◽  
Roughness Effects ◽  
Number Range ◽  
Axial Profile ◽  
Excellent Reproducibility

The effect of roughness and form was investigated for toroidal-throat sonic nozzles, using both experimental and computational techniques. Eight, 10 mm diameter nozzles were specially made to investigate the effects of deviating from ISO 9300; these nozzles were measured for diameter, axial profile, roughness and roundness in order to assess the effects on discharge coefficient, Cd. Flow calibrations have revealed that roughness effects are negligible for Ra/d ≤ 4.5×10−5 (three times the limit of ISO 9300) in the turbulent regime (Re > 106), in keeping with previously published data taken in the laminar regime. Test data from three unpolished nozzles, of average Ra of ∼ 0.3 μm, also demonstrated that excellent reproducibility in Cd vs. Re (≤ 0.04%) might be achieved without the need for polishing. Data is also presented from recent primary gravimetric calibrations of NEL’s 16 reference nozzles. The data supports the proposed equation for normally machined nozzles over the Reynolds number range tested (0.17×106 < Re < 17×106), with the standard deviation from the ISO/CD 9300 curve being 0.27% (k = 2; 95% confidence) over the range 0.35×106 < Re < 17×106, provided d ≥ 3.8 mm.

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.

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