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Vivek V. Ranade - One of the best experts on this subject based on the ideXlab platform.
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cfd simulation of gas liquid Stirred Vessel vc s33 and l33 flow regimes
Aiche Journal, 2006Co-Authors: A.r. Khopkar, Vivek V. RanadeAbstract:A comprehensive computational model based on the Eulerian-Eulerian approach was developed to simulate gas-liquid flows in a Stirred Vessel. A separate submodel was developed to quantitatively understand the influence of turbulence and presence of neighboring bubbles on drag acting on bubbles. This submodel was used to identify an appropriate correlation for estimating the interphase drag force. The standard k-e turbulence model was used to simulate turbulent gas-liquid flows in a Stirred Vessel. A computational snapshot approach was used to simulate motion of the standard Rushton turbine in a fully baffled Vessel. The computational model was mapped onto FLUENT4.5, a commercial CFD solver. The model predictions were compared with the previously published experimental data of Bombac and co-workers. The model was used to simulate three distinct flow regimes in gas-liquid Stirred Vessels: vortex clinging (VC), alternating small cavities (S33), and alternating large cavities (L33). The predicted results show reasonably good agreement with the experimental data for all three regimes. The computational model and results discussed in this work would be useful for understanding and simulating gas holdup distribution and flow regimes in Stirred Vessels.
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cfd simulation of mixing in tall gas liquid Stirred Vessel role of local flow patterns
Chemical Engineering Science, 2006Co-Authors: A.r. Khopkar, Gopal R Kasat, Aniruddha B Pandit, Vivek V. RanadeAbstract:In this work, we have used the computational fluid dynamics (CFD)-based models to investigate the gas-liquid flows generated by three down-pumping pitched blade turbines. A two-fluid model along with the standard k-e turbulence model was used to simulate the dispersed gas-liquid flow in a Stirred Vessel. Appropriate drag corrections to account for bulk turbulence [Khopkar and Ranade, 2005. CFD simulation of gas-liquid flow in a Stirred Vessel: VC, S33 and L33 flow regimes. A.I.Ch.E. Journal, accepted for publication] were developed to correctly simulate different flow regimes. The computational snapshot approach was used to simulate impeller rotation and was implemented in the commercial CFD code, FLUENT4.5 (of Fluent. Inc., USA). The computational model has successfully captured the flow regimes as observed during experiments. The particle trajectory simulations were then carried out to examine the influence of the different flow regimes on the circulation time distribution. The model predictions were verified by comparing the predicted results with the experimental data of [Shewale and Pandit, 2006. Studies in multiple impeller agitated gas-liquid contactors. Chemical Engineering Science 61, 489-504]. The computational model and results discussed in this study would be useful for explaining the implications local flow patterns on the mixing process and extending the applications of CFD models for simulating large multiphase Stirred reactors.
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CFD simulation of gas–liquid Stirred Vessel: VC, S33, and L33 flow regimes
AIChE Journal, 2006Co-Authors: A.r. Khopkar, Vivek V. RanadeAbstract:A comprehensive computational model based on the Eulerian-Eulerian approach was developed to simulate gas-liquid flows in a Stirred Vessel. A separate submodel was developed to quantitatively understand the influence of turbulence and presence of neighboring bubbles on drag acting on bubbles. This submodel was used to identify an appropriate correlation for estimating the interphase drag force. The standard k-e turbulence model was used to simulate turbulent gas-liquid flows in a Stirred Vessel. A computational snapshot approach was used to simulate motion of the standard Rushton turbine in a fully baffled Vessel. The computational model was mapped onto FLUENT4.5, a commercial CFD solver. The model predictions were compared with the previously published experimental data of Bombac and co-workers. The model was used to simulate three distinct flow regimes in gas-liquid Stirred Vessels: vortex clinging (VC), alternating small cavities (S33), and alternating large cavities (L33). The predicted results show reasonably good agreement with the experimental data for all three regimes. The computational model and results discussed in this work would be useful for understanding and simulating gas holdup distribution and flow regimes in Stirred Vessels.
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gas liquid flow generated by a rushton turbine in Stirred Vessel carpt ct measurements and cfd simulations
Chemical Engineering Science, 2005Co-Authors: Avinash R. Khopkar, Aravind Rammohan, Vivek V. Ranade, Milorad P. DudukovicAbstract:In this work, computer-automated radioactive particle tracking (CARPT), computed tomography (CT) and computational fluid dynamic (CFD) based models were used to investigate gas-liquid flow generated by a Rushton turbine. CARPT and CT measurements were carried out in a gas-liquid Stirred Vessel operating in two different flow regimes and captured the quantitative Eulerian information of gas-liquid flow. The CARPT data was then used to extract the circulation time distribution in a Vessel. A two-fluid model along with the standard k-e turbulence model was used to simulate the dispersed gas-liquid flow in a Stirred Vessel. Appropriate drag corrections to account for bulk turbulence (along the lines proposed by Brucato et al. (Chem. Eng. Sci. 45(1998) 3295)) were developed to correctly simulate different flow regimes. The computational snapshot approach was used to simulate impeller rotation and was implemented in the commercial CFD code, FLUENT4.5 (of Fluent. Inc., USA). Most model predictions compared favourably with CARPT and CT measurements. Validated CFD models as attempted in this paper are promising to simulation of industrial Stirred Vessels.
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Gas–liquid flow generated by a Rushton turbine in Stirred Vessel: CARPT/CT measurements and CFD simulations
Chemical Engineering Science, 2005Co-Authors: A.r. Khopkar, Aravind Rammohan, Vivek V. Ranade, Milorad P. DudukovicAbstract:In this work, computer-automated radioactive particle tracking (CARPT), computed tomography (CT) and computational fluid dynamic (CFD) based models were used to investigate gas-liquid flow generated by a Rushton turbine. CARPT and CT measurements were carried out in a gas-liquid Stirred Vessel operating in two different flow regimes and captured the quantitative Eulerian information of gas-liquid flow. The CARPT data was then used to extract the circulation time distribution in a Vessel. A two-fluid model along with the standard k-e turbulence model was used to simulate the dispersed gas-liquid flow in a Stirred Vessel. Appropriate drag corrections to account for bulk turbulence (along the lines proposed by Brucato et al. (Chem. Eng. Sci. 45(1998) 3295)) were developed to correctly simulate different flow regimes. The computational snapshot approach was used to simulate impeller rotation and was implemented in the commercial CFD code, FLUENT4.5 (of Fluent. Inc., USA). Most model predictions compared favourably with CARPT and CT measurements. Validated CFD models as attempted in this paper are promising to simulation of industrial Stirred Vessels.
A.r. Khopkar - One of the best experts on this subject based on the ideXlab platform.
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cfd simulation of gas liquid flows in Stirred Vessel equipped with dual rushton turbines influence of parallel merging and diverging flow configurations
Chemical Engineering Science, 2008Co-Authors: A.r. Khopkar, P A TanguyAbstract:Abstract Computational fluid dynamics (CFD) was used to investigate the influence of parallel, merging and diverging flow configurations on the gas dispersion operation in Stirred Vessel. The simulation was based on the two-fluid model along with the standard k– e turbulence model along with an appropriate drag correction to account for bulk turbulence [Khopkar, A.R., Ranade, V.V., 2006. CFD simulation of gas–liquid Stirred Vessel: VC, S33 and L33 flow regimes. A.I.Ch.E. Journal 52, 1654–1671]. The model predictions were compared with the published experimental data of Bombac, Zun [2000. Gas-filled cavity structures and local void fraction distribution in Vessel with dual-impellers. Chemical Engineering Science 55, 2995–3001] for parallel flow configuration. The predicted results show reasonably good agreement with the experimental data. The computational model was then used to simulate the gas–liquid flows for the other two flow configurations. The results of this work provide ‘a priory’ information on the implications of flow configuration on the Vessel performance.
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cfd simulation of gas liquid Stirred Vessel vc s33 and l33 flow regimes
Aiche Journal, 2006Co-Authors: A.r. Khopkar, Vivek V. RanadeAbstract:A comprehensive computational model based on the Eulerian-Eulerian approach was developed to simulate gas-liquid flows in a Stirred Vessel. A separate submodel was developed to quantitatively understand the influence of turbulence and presence of neighboring bubbles on drag acting on bubbles. This submodel was used to identify an appropriate correlation for estimating the interphase drag force. The standard k-e turbulence model was used to simulate turbulent gas-liquid flows in a Stirred Vessel. A computational snapshot approach was used to simulate motion of the standard Rushton turbine in a fully baffled Vessel. The computational model was mapped onto FLUENT4.5, a commercial CFD solver. The model predictions were compared with the previously published experimental data of Bombac and co-workers. The model was used to simulate three distinct flow regimes in gas-liquid Stirred Vessels: vortex clinging (VC), alternating small cavities (S33), and alternating large cavities (L33). The predicted results show reasonably good agreement with the experimental data for all three regimes. The computational model and results discussed in this work would be useful for understanding and simulating gas holdup distribution and flow regimes in Stirred Vessels.
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cfd simulation of mixing in tall gas liquid Stirred Vessel role of local flow patterns
Chemical Engineering Science, 2006Co-Authors: A.r. Khopkar, Gopal R Kasat, Aniruddha B Pandit, Vivek V. RanadeAbstract:In this work, we have used the computational fluid dynamics (CFD)-based models to investigate the gas-liquid flows generated by three down-pumping pitched blade turbines. A two-fluid model along with the standard k-e turbulence model was used to simulate the dispersed gas-liquid flow in a Stirred Vessel. Appropriate drag corrections to account for bulk turbulence [Khopkar and Ranade, 2005. CFD simulation of gas-liquid flow in a Stirred Vessel: VC, S33 and L33 flow regimes. A.I.Ch.E. Journal, accepted for publication] were developed to correctly simulate different flow regimes. The computational snapshot approach was used to simulate impeller rotation and was implemented in the commercial CFD code, FLUENT4.5 (of Fluent. Inc., USA). The computational model has successfully captured the flow regimes as observed during experiments. The particle trajectory simulations were then carried out to examine the influence of the different flow regimes on the circulation time distribution. The model predictions were verified by comparing the predicted results with the experimental data of [Shewale and Pandit, 2006. Studies in multiple impeller agitated gas-liquid contactors. Chemical Engineering Science 61, 489-504]. The computational model and results discussed in this study would be useful for explaining the implications local flow patterns on the mixing process and extending the applications of CFD models for simulating large multiphase Stirred reactors.
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CFD simulation of gas–liquid Stirred Vessel: VC, S33, and L33 flow regimes
AIChE Journal, 2006Co-Authors: A.r. Khopkar, Vivek V. RanadeAbstract:A comprehensive computational model based on the Eulerian-Eulerian approach was developed to simulate gas-liquid flows in a Stirred Vessel. A separate submodel was developed to quantitatively understand the influence of turbulence and presence of neighboring bubbles on drag acting on bubbles. This submodel was used to identify an appropriate correlation for estimating the interphase drag force. The standard k-e turbulence model was used to simulate turbulent gas-liquid flows in a Stirred Vessel. A computational snapshot approach was used to simulate motion of the standard Rushton turbine in a fully baffled Vessel. The computational model was mapped onto FLUENT4.5, a commercial CFD solver. The model predictions were compared with the previously published experimental data of Bombac and co-workers. The model was used to simulate three distinct flow regimes in gas-liquid Stirred Vessels: vortex clinging (VC), alternating small cavities (S33), and alternating large cavities (L33). The predicted results show reasonably good agreement with the experimental data for all three regimes. The computational model and results discussed in this work would be useful for understanding and simulating gas holdup distribution and flow regimes in Stirred Vessels.
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Gas–liquid flow generated by a Rushton turbine in Stirred Vessel: CARPT/CT measurements and CFD simulations
Chemical Engineering Science, 2005Co-Authors: A.r. Khopkar, Aravind Rammohan, Vivek V. Ranade, Milorad P. DudukovicAbstract:In this work, computer-automated radioactive particle tracking (CARPT), computed tomography (CT) and computational fluid dynamic (CFD) based models were used to investigate gas-liquid flow generated by a Rushton turbine. CARPT and CT measurements were carried out in a gas-liquid Stirred Vessel operating in two different flow regimes and captured the quantitative Eulerian information of gas-liquid flow. The CARPT data was then used to extract the circulation time distribution in a Vessel. A two-fluid model along with the standard k-e turbulence model was used to simulate the dispersed gas-liquid flow in a Stirred Vessel. Appropriate drag corrections to account for bulk turbulence (along the lines proposed by Brucato et al. (Chem. Eng. Sci. 45(1998) 3295)) were developed to correctly simulate different flow regimes. The computational snapshot approach was used to simulate impeller rotation and was implemented in the commercial CFD code, FLUENT4.5 (of Fluent. Inc., USA). Most model predictions compared favourably with CARPT and CT measurements. Validated CFD models as attempted in this paper are promising to simulation of industrial Stirred Vessels.
R Mann - One of the best experts on this subject based on the ideXlab platform.
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development of a networks of zones fluid mixing model for an unbaffled Stirred Vessel used for precipitation
Chemical Engineering Science, 2006Co-Authors: M. Kagoshima, R MannAbstract:Abstract Reactive acid–alkali tracers have been deployed to capture the macromixing and partial segregation behaviour in an unbaffled Stirred Vessel. This configuration is often used in precipitators to avoid inadvertent solid accretions on Vessel internals. The macromixing behaviour for semi-batch addition with visualisation of reactive (acid–alkali) tracers has been acquired via video images which are rendered visible using phenolphthalein as indicator. By means of visual reality modelling, in which computer graphics are used to reconstruct and closely mimic the experimentally visualised fluid mixing “scenes”, the parameters for a networks-of-zones mixing model for the unbaffled semi-batch case have been established. The model can then be used for predicting precipitation behaviour for single-jet and other modes of operation. Some illustrative examples for barium sulphate, showing the underlying supersaturation fields in 3-D and the consequent time evolving particle size distributions, are presented and discussed for a single jet case.
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measurements of gas liquid mixing in a Stirred Vessel using electrical resistance tomography ert
Chemical Engineering Journal, 2000Co-Authors: Mi Wang, Andrew Dorward, D Vlaev, R MannAbstract:Abstract The non-invasive measurement of mixing inside a Stirred Vessel in 3-D, using an 8 × 16 array of resistance tomography sensors, provides powerful opportunities for characterising and quantifying the process complexities [R. Mann, F.J. Dickin, M. Wang, T. Dyakowski, R.A. Forrest, P.J. Holden, Chem. Eng. Sci. 52 (1997) 2087–2097; P.J. Holden, M. Wang, R. Mann, F.J. Dickin, R.B. Edwards, A.I.Ch.E. JI. 44 (1998) 780–790]. Using the UMIST pilot plant 1.5 m Stirred Vessel, new results are presented for gas–liquid mixing which can distinguish differences in liquid mixing behavior between water (low viscosity) and relatively viscous 0.05% carbopol solution. The slower liquid phase tracer mixing rates for the viscous case compared with water, as well as differences in the pattern of mixing, can be readily observed and portrayed in 3-D using linear back projection for the reconstruction. In addition, the variation of local gas hold-up (voidage) can also be simultaneously measured by identifying regions within the Vessel which have high or low local conductivity/resistivity. Electrical resistance tomography (ERT) can thus provide simultaneous detailed information on two aspects of gas–liquid mixing, involving the isolation of liquid phase mixing when gas–liquid mixing is taking place. The ERT results can be processed to provide the local mixing curve, hence mixing times, for any nominated pixel.
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visual 3 d modelling of Stirred Vessel mixing for an inclined blade impeller
Chemical Engineering Research & Design, 2000Co-Authors: Masoud Rahimi, P R, R MannAbstract:The 3-D visualization of passive tracer mixing inside a Stirred Vessel offers a powerful means of validating computational models. Taken together, the forward elevation and underneath plan views (acquired by a 45° mirror) of the mixing of a visible tracer in space and time, captured on video, present approximately 0.1Mb of data per video frame. This density of potentially quantitative concentration field information is very suitable for validation of computational fluid mixing (CFM) predictions for models comprised of the order of 10 5 voxels. New results are presented for an axial pumping 45° inclined-blade turbine in a semi-tech 30 dm 3 Vessel equipped for 3-D visualization. Passive scalar mixing tests have been evaluated using an improved networks-of-zones model with 32,000 zones. Conformal stretching of the radial flow configuration of existing software provides a simple way of accommodating the predominantly axial flow pattern. Good agreement between theory and experiment has been demonstrated using AVS graphics, giving see-through close to photo-realism reconciliation of mixing images for two different injection positions.
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on detecting mixing pathologies inside a Stirred Vessel using electrical resistance tomography
Chemical Engineering Research & Design, 1999Co-Authors: P J Holden, Mi Wang, R Mann, F J Dickin, Ruth EdwardsAbstract:Electrical resistance tomography (ERT) has the capability to resolve the 3-D conductivity field inside a Stirred mixing Vessel using multiple planes of axially spaced sensors. This capability has already been exploited to qualitatively image vortex formation and geometry, pseudo-stationary gas-liquid mixing and unsteady dynamic brine tracer mixing inside a plant scale (1.5 m) Stirred Vessel (Mann et al , 1997 1 ). This feature of qualitative imaging, arising from simplified reconstruction by back-projection, nevertheless can visualize key features of mixing characteristics without the need to resort to extensive iterations to converge on quantitative images. This approach is therefore useful in detecting and identifying pathological behaviour caused by equipment malfunction. Examples are presented for (i) misplaced gas sparger, (ii) inadvertent solids accumulation and (iii) displaced feed point behind a baffle.
Milorad P. Dudukovic - One of the best experts on this subject based on the ideXlab platform.
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gas liquid flow generated by a rushton turbine in Stirred Vessel carpt ct measurements and cfd simulations
Chemical Engineering Science, 2005Co-Authors: Avinash R. Khopkar, Aravind Rammohan, Vivek V. Ranade, Milorad P. DudukovicAbstract:In this work, computer-automated radioactive particle tracking (CARPT), computed tomography (CT) and computational fluid dynamic (CFD) based models were used to investigate gas-liquid flow generated by a Rushton turbine. CARPT and CT measurements were carried out in a gas-liquid Stirred Vessel operating in two different flow regimes and captured the quantitative Eulerian information of gas-liquid flow. The CARPT data was then used to extract the circulation time distribution in a Vessel. A two-fluid model along with the standard k-e turbulence model was used to simulate the dispersed gas-liquid flow in a Stirred Vessel. Appropriate drag corrections to account for bulk turbulence (along the lines proposed by Brucato et al. (Chem. Eng. Sci. 45(1998) 3295)) were developed to correctly simulate different flow regimes. The computational snapshot approach was used to simulate impeller rotation and was implemented in the commercial CFD code, FLUENT4.5 (of Fluent. Inc., USA). Most model predictions compared favourably with CARPT and CT measurements. Validated CFD models as attempted in this paper are promising to simulation of industrial Stirred Vessels.
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Gas–liquid flow generated by a Rushton turbine in Stirred Vessel: CARPT/CT measurements and CFD simulations
Chemical Engineering Science, 2005Co-Authors: A.r. Khopkar, Aravind Rammohan, Vivek V. Ranade, Milorad P. DudukovicAbstract:In this work, computer-automated radioactive particle tracking (CARPT), computed tomography (CT) and computational fluid dynamic (CFD) based models were used to investigate gas-liquid flow generated by a Rushton turbine. CARPT and CT measurements were carried out in a gas-liquid Stirred Vessel operating in two different flow regimes and captured the quantitative Eulerian information of gas-liquid flow. The CARPT data was then used to extract the circulation time distribution in a Vessel. A two-fluid model along with the standard k-e turbulence model was used to simulate the dispersed gas-liquid flow in a Stirred Vessel. Appropriate drag corrections to account for bulk turbulence (along the lines proposed by Brucato et al. (Chem. Eng. Sci. 45(1998) 3295)) were developed to correctly simulate different flow regimes. The computational snapshot approach was used to simulate impeller rotation and was implemented in the commercial CFD code, FLUENT4.5 (of Fluent. Inc., USA). Most model predictions compared favourably with CARPT and CT measurements. Validated CFD models as attempted in this paper are promising to simulation of industrial Stirred Vessels.
S. J. Stanley - One of the best experts on this subject based on the ideXlab platform.
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tomographic imaging during reactive precipitation in a Stirred Vessel mixing with chemical reaction
Chemical Engineering Science, 2006Co-Authors: S. J. StanleyAbstract:Abstract Electrical resistance tomography (ERT) allows the user to non-invasively ‘see inside their process’ through the manipulation and measurement of electrical properties enabling a powerful real-time visualisation of the time evolving three-dimensional conductivity distributions within the process unit. A 4-plane 16-sensor ERT array retrofitted to a 7.5 l Stirred Vessel has been used to rigorously interrogate the single feed semi-batch precipitation of barium sulphate, providing over 1000 spatially varying data points per ‘captured’ frame. A variety of reactant concentrations and agitation intensities were investigated. The results obtained reflect both the hydrodynamics and complex reaction kinetics involved with reactions and detail a number of very distinct regions during the experimental runs. This is achieved through the direct visualisation of the induced feed plume, quantification of the homogeneity (‘mixedness’) within the Vessel, time evolving conductivity trends and a further analysis into the rates of conductivity changes as the reaction proceeds. For some experimental runs the predicted conductivity trends for a perfectly mixed state have been calculated using a conductivity–concentration correlation. ERT offers many spatially varying data points as opposed to point wise measurements which offers a significant improvement for the validation of mathematical models which attempt to deal with reactive crystallisation. As well as data collection, specifically for model validation, ERT may offer the means to control the spatio-temporal distributions of reactants and phases within the reactor to aid the suppression of unwanted by-products for industrial processes whilst offering a means to monitor the process unit to ensure the required mixing intensity is always achieved. Also included is an analysis of the mean volume diameter of the precipitate for each experimental run with scanning electron microscope (SEM) images.
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Tomographic Imaging of Fluid Mixing in Three Dimensions for Single-Feed Semi-Batch Operation of a Stirred Vessel
Chemical Engineering Research and Design, 2002Co-Authors: S. J. Stanley, Reginald Mann, K. PrimroseAbstract:With fast data acquisition and good spatial discrimination, electrical resistance tomography (ERT) provides a non-invasive and non-intrusive technique to interrogate, in three dimensions, the concentration fields inside a typical Stirred Vessel. A newly refurbished vertically assembled 16-sensor eight-ring electrode array has been used to image the full volume of a 23001 pilot-scale Vessel for single-feed semi-batch operation. Images reconstructed from the raw ERT data are represented first as pixel conductivity distributions and secondly as time incremented three-dimensional solid-body colour-scaled isosurfaces thereby providing a five-dimensional representation of the mixing process. When operating in this single-feed semi-batch mode, the ERT system can clearly distinguish the higher conductivity feed plume. The ERT also images the subsequent mixing in the Vessel after the semi-batch feed addition has stopped, thus additionally characterizing the role of macro-mixing in achieving final homogeneity after a period of semi-batch operation. The results to be presented are extremely useful for the validation of CFD predictions of mixing behaviour.