Rushton Turbine

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Alvin W Nienow - One of the best experts on this subject based on the ideXlab platform.

  • using positron emission particle tracking pept to study the turbulent flow in a baffled vessel agitated by a Rushton Turbine improving data treatment and validation
    Chemical Engineering Research & Design, 2011
    Co-Authors: Fabio Chiti, Mostafa Barigou, Serafim Bakalis, Waldemar Bujalski, Archie Eaglesham, Alvin W Nienow
    Abstract:

    Abstract Positron emission particle tracking (PEPT) is a relatively new technique allowing the quantitative study of flow phenomena in three dimensions in opaque systems that cannot be studied by optical methods such as particle image velocimetry (PIV) or laser Doppler anemometry (LDA). Here, velocity measurements made using PEPT in two sizes of baffled vessel (∼0.20 m and ∼0.29 m diameter) and two different viscosity fluids agitated by a Rushton Turbine are compared for the first time directly in depth with some studies reported in the literature made by LDA for the turbulent regime in the equivalent geometry. Initially, the paper considers how the Lagrangian data obtained by PEPT can be converted into Eulerian in order to make the comparison most effective. It also considers ways of data treatment that improve the accuracy of both the raw PEPT data and the velocities determined from it. It is shown that excellent agreement is found between the PEPT and literature results, especially for the smaller vessel, except for the radial velocity just off the tip of the blade in the plane of the disc of the Rushton Turbine. This difference is attributed to the very rapid changes in both magnitude and direction that occurs in that region and also to the different way of ensemble averaging in the two techniques. In addition, the results for the absolute velocities normalised by the impeller tip velocity for all the rectangular cross-section toroidal cells in each size of vessel and each fluid and a range of agitator speeds are compared in the form of frequency histograms. In this analysis, the velocities for each run are obtained from PEPT based on tracking a particle for 30 min and the mean and mode of the velocities each decrease slightly with decreasing scale and Reynolds number. The possible reasons for this variation in the mode and the mean are discussed. Overall, it is concluded that for the radial flow Rushton Turbine the PEPT technique can be used to obtain accurate velocity data throughout the entire complex three-dimensional turbulent flow field in an agitated, baffled vessel except very close to the impeller in the radial discharge stream.

  • macro and micromixing studies in an unbaffled vessel agitated by a Rushton Turbine
    Chemical Engineering Science, 2008
    Co-Authors: Melissa Assirelli, Archie Eaglesham, Waldemar Bujalski, Alvin W Nienow
    Abstract:

    Abstract Macromixing characteristics, power number and visual observation of the vortex behaviour and micromixing in an unbaffled tank agitated with a Rushton Turbine are reported. The latter has also been compared in detail with earlier results from an identical tank containing baffles. The maximum mean specific energy dissipation rate, e ¯ T , in the unbaffled tank that can be utilised without severe air incorporation is ∼ 0.18 W / kg compared to ∼ 1.2 W / kg with baffles. However, at this lower e ¯ T , the micromixing efficiency is always significantly greater without baffles except when addition is made onto the top of the liquid or into the trailing vortex very close to the impeller. In these latter cases, they are approximately the same but even a small submergence of the feed tube below the liquid surface greatly enhances micromixing in the unbaffled case whilst it is still very poor with baffles. This good micromixing performance of the unbaffled vessel was very unexpected. Furthermore, an established method of estimating the local e T gave values of e T / e ¯ T = φ ⪢ 1 at every feed position where measurement was undertaken. Since the spatially averaged value of φ = 1 , this result suggests the possibility that the accepted concept of micromixing being totally controlled by the local e T at the feed point may not be valid for such swirling flows.

  • study of micromixing in a stirred tank using a Rushton Turbine comparison of feed positions and other mixing devices
    Chemical Engineering Research & Design, 2002
    Co-Authors: Melissa Assirelli, Archie Eaglesham, Waldemar Bujalski, Alvin W Nienow
    Abstract:

    The consecutive-competing iodide-iodate reaction scheme has been used to study micromixing phenomena in a baffled vessel of 0.29 m diameter agitated by a Rushton Turbine. It has been confirmed that, by using successive injections, this reaction scheme is very efficient for such a study. Four agitator speeds giving mean specific energy dissipation rates, e T from ∼0.2 to ∼1.2 W/kg have been used, with sub-surface feeding at one of four points. For a given speed, addition at each of these four points gave different local values of e T , ranging from less than e T very close to the top of the liquid to much greater close to the impeller. The point closest to the impeller was chosen to be such that feeding was estimated to be at the point of maximum e T . For the maximum speed, the segregation index, as a measure of the amount of waste product, was ∼20% with feed at the top of the liquid (as preferred industrially because of its convenience). This waste was reduced to ∼5% by feeding at the point of maximum e T close to the impeller. A comparison was also made with results reported in the literature using the same reaction for two new devices developed for improved micromixing. By feeding at the carefully chosen position close to the impeller, the results with the Rushton Turbine were as good as or better than with the special devices even at the comparatively low e T of ∼1.2 W/kg. It was estimated that the maximum local specific energy dissipation rate was ∼70 times the mean, in reasonable agreement with a very recent study where the same pair of reactions and LDV were both used.

  • instabilities when using a standard t 3 Rushton Turbine for stirring as foam disruption safd
    Canadian Journal of Chemical Engineering, 2000
    Co-Authors: Lotte A Boon, Waldemar Bujalski, Frans W J M M Hoeks, Rob G J M Van Der Lans, Alvin W Nienow
    Abstract:

    The concept of using the upper stirrer for foam disruption in a bioreactor agitated by multiple impellers has recently been published by Hoeks et al. (1997). This concept, stirring as foam disruption (SAFD), was shown by them to be effective with a range of impellers. However, the commonly used (so-called) standard Rushton Turbine of one-third the fermenter diameter was not included. This paper fills that important gap. By measuring the foam height, the holdup, the power draw and the velocities of the liquid in the dispersion just below its top surface, it is concluded that the SAFD concept does not work well with the standard Rushton Turbine. This is because the amount of broth for which foam can be disrupted is less than that found with all the other impellers tested to date; and even when foam disruption occurs, significant flow instabilities and torque fluctuations are found. Perhaps the poor performance of this impeller, which has been used so frequently in industry and in academic studies, explains why the concept of SAFD was not developed earlier. Le concept qui consiste a utiliser l'agitateur superieur pour desintegrer la mousse dans un bioreacteur agite par des Turbines multiples a ete publie recemment par Hoeks et al. (1997). Ceux-ci ont montre que ce concept d'agitation comme moyen de desintegrer la mousse (concept SAFD) etait efficace avec differentes Turbines. Cependant, la Turbine Rushton standard communement utilisee dont le diametre correspond a un tiers de celui du fermenteur, n'est pas incluse. Cet article vise a combler cette lacune importante. En mesurant la hauteur de mousse, la retention, la consommation de puissance et les vitesses du liquide dans la dispersion juste en dessous de sa surface superieure, on conclut que le concept de SAFD ne marche pas bien avec la Turbine Rushton standard. Cela est du au fait que la quantite de bouillon pour laquelle la mousse peut etre desintegree est inferieure a la quantite qu'on trouve dans toutes les autres Turbines testees jusqu'a ce jour; et meme lorsqu'il y a desintegration de la mousse, des instabilites d'ecoulement et des fluctuations de couple importantes sont observees. Sans doute la pietre performance de cette Turbine, qui est si frequemment utilisee dans l'industrie et les etudes scientifiques, explique pourquoi le concept de SAFD n'a pas ete developpe plus tot.

  • bubble sizes and coalescence rates in an aerated vessel agitated by a Rushton Turbine
    Journal of Chemical Engineering of Japan, 1993
    Co-Authors: Koji Takahashi, Alvin W Nienow
    Abstract:

    For an improved understanding of gas-liquid mass transfer in a stirred-tank reactor and its spatial variation, knowledge of local bubble sizes (mean and distribution), gas holdups and coalescence rate is very important.In this work, bubble sizes at eight positions in an aerated vessel agitated by a 6-blade Rushton Turbine were measured for an air-deionized water system by using flash photography. Bubble sizes near the vessel wall (and especially near the baffles) or in the upper levels of the vessel were more than four times those in the impeller region, The number of bubbles was also counted in a given area, and the population density was determined knowing the depth of focus.The coalescence rate during passage of the bubbles from the impeller to the vessel wall was calculated for different gases and liquids by measuring bubble sizes on photographs taken across the annular plane. It was found that coalescence occurs very near the impeller. The calculated values of coalescence rate were almost the same as those reported earlier by other investigators.

Vivek V Ranade - One of the best experts on this subject based on the ideXlab platform.

  • a novel local singularity distribution based method for flow regime identification gas liquid stirred vessel with Rushton Turbine
    Chemical Engineering Science, 2006
    Co-Authors: A M Jade, Vivek V Ranade, Valadi K Jayaraman, B D Kulkarni, A R Khopkar, Ashutosh Sharma
    Abstract:

    A novel method employing a unique combination of wavelet based local singularity analysis and support vector machines (SVM) classification is described and illustrated by considering the case example of flow regime identification in gas-liquid stirred tank equipped with Rushton Turbine. Pressure fluctuations time series data obtained at different operating conditions were first analyzed to obtain the distribution of local Holder exponents' estimates. The relevant features from this distribution were then used as input data to the SVM classifier. Employing this method we could classify flow regimes with 98% accuracy. The results highlight the fact that the local scaling behavior of a given regime follows a distinct pattern. Further, the singularity features can be employed by intelligent machine learning based algorithms like SVM for successful online regime identification. The method can be readily applied to the other multiphase systems like bubble column, fluidized bed, etc.

  • gas liquid flow generated by a Rushton Turbine in stirred vessel carpt ct measurements and cfd simulations
    Chemical Engineering Science, 2005
    Co-Authors: A R Khopkar, Vivek V Ranade, Aravind Rammohan, M P Dudukovic
    Abstract:

    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.

  • influence of gas flow rate on the structure of trailing vortices of a Rushton Turbine piv measurements and cfd simulations
    Chemical Engineering Research & Design, 2001
    Co-Authors: Vivek V Ranade, M Perrard, Le N Sauze, C Xuereb, J Bertrand
    Abstract:

    Trailing vortices behind rotating impeller blades play crucial role in determining gas accumulation behind them. The gas accumulation behind blades affects the pumping and power dissipation capacity of the impeller and thus significantly affects the performance of gas–liquid stirred reactors. Understanding fluid dynamic characteristics of these trailing vortices and capability to computationally simulate these vortices is, therefore, essential for reliable design and scale-up of stirred reactors. In this paper, we have used particle image velocimetry (PIV) technique and CFD model based on computational snapshot approach for systematically studying influence of gas flow rate on structure of trailing vortices behind blades of a Rushton Turbine. PIV measurements were carried out in a standard, fully baffled stirred vessel (H/T= 1) with a flat bottom. Vessel diameter was 0.4 m. A six bladed standard Rushton Turbine was placed at one third of liquid height with a ring sparger. Four baffles of 1/10 T width were placed at equal spacing. Tap water was used as a medium in the vessel. Measurements were carried out at five different gas flow rates to vary the dimensionless gas flow number in the range of 0.01 to 0.06. Both, angle resolved and angle averaged flow fields near the impeller blades were measured. The structure of trailing vortices in presence of gas was studied in detail. A Eulerian–Eulerian, two fluid model was used to simulate dispersed gas–liquid flow in stirred vessel. A computational snapshot approach was used to simulate impeller rotation. The computational model was implemented using the commercial CFD code, FLUENT (of Fluent Inc., USA) with the help of user defined subroutines. The computational model was used to simulate flow in stirred vessel operating under conditions used in the experiments. The results of this study will have important implications for extending the applicability of CFD models for simulating multiphase stirred reactors.

  • trailing vortices of Rushton Turbine piv measurements and cfd simulations with snapshot approach
    Chemical Engineering Research & Design, 2001
    Co-Authors: Vivek V Ranade, M Perrard, Le N Sauze, C Xuereb, J Bertrand
    Abstract:

    Understanding fluid dynamic characteristics of trailing vortices behind impeller blades and the capability to computationally simulate these vortices is essential for reliable design and scale-up of stirred reactors. In this paper, trailing vortices behind the blades of a standard Rushton Turbine were studied using particle image velocimetry (PIV). Angle resolved and angle averaged flow fields near the impeller blades were measured and the structure of trailing vortices was studied in detail. A computational snapshot approach of Ranade and Dommeti was extended and used to simulate flow generated by the Rushton Turbine in baffled stirred vessels. The approach was implemented using the commercial CFD code, FLUENT (of Fluent Inc, USA). Two turbulence models, namely, standard k – ɛ model and renormalization group version (RNG) of k – ɛ model were used for simulating the flow in stirred vessels. Predicted results were compared with the angle resolved PIV measurements to examine whether the computational model captures the flow structures around impeller blades. Predicted results were also compared with the angle averaged PIV data. Predicted gross flow characteristics like pumping number were also compared with the present and previously published experimental data. The results and conclusions drawn from this study will have important implications for extending the applicability of CFD models for simulating flow near impeller blades.

  • an efficient computational model for simulating flow in stirred vessels a case of Rushton Turbine
    Chemical Engineering Science, 1997
    Co-Authors: Vivek V Ranade
    Abstract:

    Abstract Computational tools are being increasingly used to analyse flow and mixing in baffled stirred vessels. In a baffled stirred vessel, flow around the rotating impeller blades interacts with stationary baffles and generates a complex, three-dimensional, recirculating turbulent flow. We have developed an efficient computational model, in which a quasi-steady flow is computed for any momentary impeller position. This model adequately captures most of the significant details of the flow both within and outside the impeller without requiring any empirical input/ adjustable parameter. The method was applied to the flow generated by a standard Rushton Turbine, for which detailed experimental data are available. A case of fully baffled vessel with standard Rushton Turbine (DT) was simulated using FLUENT code. The impeller rotation was modelled in terms of appropriate source terms at the blade surfaces. The laminar and turbulent flow generated by DT were simulated using this model. The model predictions were validated by comparisons with the published experimental data. Overall impleller performance characteristics like pumping number and power number were also compared with the experimental data for both, laminar and turbulent flow regimes. The approach presented here can be used as a general purpose, mixer design tool.

Alain Line - One of the best experts on this subject based on the ideXlab platform.

  • trailing vortices generated by a Rushton Turbine assessment of urans and large eddy simulations
    Chemical Engineering Research & Design, 2009
    Co-Authors: Angelique Delafosse, Jerome Morchain, Pascal Guiraud, Alain Line
    Abstract:

    The discharge flow of a Rushton Turbine is characterized by the formation of coherent vortex structures induced by the blade motion and called trailing vortices. The objective here is to assess the ability of computational fluid dynamics (CFD) to represent the trailing vortices and their relationship with turbulence properties. To this end, two simulations have been realized: an unsteady Reynolds-Averaged Navier-Stokes (URANS) simulation and a Large Eddy Simulation (LES) simulation. The trajectory of the trailing vortices predicted by the simulations has been compared with previous works. This comparison shows that the URANS simulation does not predict properly the trailing vortices while the LES results are very close to the experimental ones. As a consequence, the turbulence properties spatially correlated to the trailing vortices are well predicted by LES but not by URANS simulation.

  • Turbulent Macroscale in the Impeller Stream of a Rushton Turbine
    10th European Conference on Mixing, 2007
    Co-Authors: Renaud Escudie, Alain Line, Michel Roustan
    Abstract:

    Publisher Summary Particle Image Velocimetry (P.I.V.) technique is used in mechanically agitated tank equipped with a Rushton Turbine. This chapter focuses on the analysis of the flow field in terms of mean flow and fluctuating motion. The fluctuations are expressed in terms of turbulence (random fluctuation) and pseudoturbulence (fluctuation induced by the periodic motion of the blades). From instantaneous velocity field taken in a plane with at given angles relative to the position of the blade, it is possible to derive spatial two-point velocity correlation functions in order to deduce integral length scales of turbulence and local dissipation rate of turbulent kinetic energy. P.I.V. technique is based on the following steps—seeding the fluid flow volume under investigation, illuminating a slide of the flow field with a pulsing light sheet, recording two images of the fluid flow with a short time interval between them, using a numerical CCD camera, and finally, processing these images by dividing the whole images into interrogation areas and using inter correlation techniques to get the instantaneous velocity field. The kinetic energy of each component of these fluctuations is determined. P.I.V. is used to estimate integral length scale of turbulence and local dissipation rate of turbulent kinetic energy. The state of the turbulence is also analyzed to estimate the influence of the blade motion in terms of anisotropy.

  • characterization of trailing vortices generated by a Rushton Turbine
    Aiche Journal, 2004
    Co-Authors: Renaud Escudie, Denis Bouyer, Alain Line
    Abstract:

    The discharge flow of a Rushton Turbine is characterized by a counter-rotating vortex pair generated behind the impeller blade. The objective here is to characterize these trailing vortices. To this end, PIV measurements were synchronized with blade position. These measurements were performed to identify and locate the trailing vortices, according to an identification technique proposed to detect a vortical region. The advantage of this method for determining the trailing vortex is highlighted after comparison to previous techniques. The trajectory of the vortices is deduced and it is shown to follow the phase-averaged velocity field induced by the impeller. The trailing vortices were characterized in terms of size and velocity circulation within the vortex. The interactions between these organized structures and turbulence were also illustrated. © 2004 American Institute of Chemical Engineers AIChE J, 50: 75– 86, 2004

Ralf Takors - One of the best experts on this subject based on the ideXlab platform.

  • Modeling of gas–liquid mass transfer in a stirred tank bioreactor agitated by a Rushton Turbine or a new pitched blade impeller
    Bioprocess and Biosystems Engineering, 2014
    Co-Authors: Ricardo Gelves, A. Dietrich, Ralf Takors
    Abstract:

    A combined computational fluid dynamics (CFD) and population balance model (PBM) approach has been applied to simulate hydrodynamics and mass transfer in a 0.18 m^3 gas–liquid stirred bioreactor agitated by (1) a Rushton Turbine, and (2) a new pitched blade geometry with rotating cartridges. The operating conditions chosen were motivated by typical settings used for culturing mammalian cells. The effects of turbulence, rotating flow, bubbles breakage and coalescence were simulated using the k –ε, multiple reference frame (MRF), Sliding mesh (SM) and PBM approaches, respectively. Considering the new pitched blade geometry with rotating aeration microspargers, $$k_{\text{L}} a$$ k L a mass transfer was estimated to be 34 times higher than the conventional Rushton Turbine set-up. Notably, the impeller power consumption was modeled to be about 50 % lower. Independent $$k_{\text{L}} a$$ k L a measurements applying the same operational conditions confirmed this finding. Motivated by these simulated and experimental results, the new aeration and stirring device is qualified as a very promising tool especially useful for cell culture applications which are characterized by the challenging problem of achieving relatively high mass transfer conditions while inserting only low stirrer energy.

  • modeling of gas liquid mass transfer in a stirred tank bioreactor agitated by a Rushton Turbine or a new pitched blade impeller
    Bioprocess and Biosystems Engineering, 2014
    Co-Authors: Ricardo Gelves, A. Dietrich, Ralf Takors
    Abstract:

    A combined computational fluid dynamics (CFD) and population balance model (PBM) approach has been applied to simulate hydrodynamics and mass transfer in a 0.18 m3 gas–liquid stirred bioreactor agitated by (1) a Rushton Turbine, and (2) a new pitched blade geometry with rotating cartridges. The operating conditions chosen were motivated by typical settings used for culturing mammalian cells. The effects of turbulence, rotating flow, bubbles breakage and coalescence were simulated using the k–e, multiple reference frame (MRF), Sliding mesh (SM) and PBM approaches, respectively. Considering the new pitched blade geometry with rotating aeration microspargers, \(k_{\text{L}} a\) mass transfer was estimated to be 34 times higher than the conventional Rushton Turbine set-up. Notably, the impeller power consumption was modeled to be about 50 % lower. Independent \(k_{\text{L}} a\) measurements applying the same operational conditions confirmed this finding. Motivated by these simulated and experimental results, the new aeration and stirring device is qualified as a very promising tool especially useful for cell culture applications which are characterized by the challenging problem of achieving relatively high mass transfer conditions while inserting only low stirrer energy.

  • Modeling of gas–liquid mass transfer in a stirred tank bioreactor agitated by a Rushton Turbine or a new pitched blade impeller
    Bioprocess and Biosystems Engineering, 2013
    Co-Authors: Ricardo Gelves, A. Dietrich, Ralf Takors
    Abstract:

    A combined computational fluid dynamics (CFD) and population balance model (PBM) approach has been applied to simulate hydrodynamics and mass transfer in a 0.18 m3 gas–liquid stirred bioreactor agitated by (1) a Rushton Turbine, and (2) a new pitched blade geometry with rotating cartridges. The operating conditions chosen were motivated by typical settings used for culturing mammalian cells. The effects of turbulence, rotating flow, bubbles breakage and coalescence were simulated using the k–e, multiple reference frame (MRF), Sliding mesh (SM) and PBM approaches, respectively. Considering the new pitched blade geometry with rotating aeration microspargers, \(k_{\text{L}} a\) mass transfer was estimated to be 34 times higher than the conventional Rushton Turbine set-up. Notably, the impeller power consumption was modeled to be about 50 % lower. Independent \(k_{\text{L}} a\) measurements applying the same operational conditions confirmed this finding. Motivated by these simulated and experimental results, the new aeration and stirring device is qualified as a very promising tool especially useful for cell culture applications which are characterized by the challenging problem of achieving relatively high mass transfer conditions while inserting only low stirrer energy.

Ricardo Gelves - One of the best experts on this subject based on the ideXlab platform.

  • Modeling of gas–liquid mass transfer in a stirred tank bioreactor agitated by a Rushton Turbine or a new pitched blade impeller
    Bioprocess and Biosystems Engineering, 2014
    Co-Authors: Ricardo Gelves, A. Dietrich, Ralf Takors
    Abstract:

    A combined computational fluid dynamics (CFD) and population balance model (PBM) approach has been applied to simulate hydrodynamics and mass transfer in a 0.18 m^3 gas–liquid stirred bioreactor agitated by (1) a Rushton Turbine, and (2) a new pitched blade geometry with rotating cartridges. The operating conditions chosen were motivated by typical settings used for culturing mammalian cells. The effects of turbulence, rotating flow, bubbles breakage and coalescence were simulated using the k –ε, multiple reference frame (MRF), Sliding mesh (SM) and PBM approaches, respectively. Considering the new pitched blade geometry with rotating aeration microspargers, $$k_{\text{L}} a$$ k L a mass transfer was estimated to be 34 times higher than the conventional Rushton Turbine set-up. Notably, the impeller power consumption was modeled to be about 50 % lower. Independent $$k_{\text{L}} a$$ k L a measurements applying the same operational conditions confirmed this finding. Motivated by these simulated and experimental results, the new aeration and stirring device is qualified as a very promising tool especially useful for cell culture applications which are characterized by the challenging problem of achieving relatively high mass transfer conditions while inserting only low stirrer energy.

  • modeling of gas liquid mass transfer in a stirred tank bioreactor agitated by a Rushton Turbine or a new pitched blade impeller
    Bioprocess and Biosystems Engineering, 2014
    Co-Authors: Ricardo Gelves, A. Dietrich, Ralf Takors
    Abstract:

    A combined computational fluid dynamics (CFD) and population balance model (PBM) approach has been applied to simulate hydrodynamics and mass transfer in a 0.18 m3 gas–liquid stirred bioreactor agitated by (1) a Rushton Turbine, and (2) a new pitched blade geometry with rotating cartridges. The operating conditions chosen were motivated by typical settings used for culturing mammalian cells. The effects of turbulence, rotating flow, bubbles breakage and coalescence were simulated using the k–e, multiple reference frame (MRF), Sliding mesh (SM) and PBM approaches, respectively. Considering the new pitched blade geometry with rotating aeration microspargers, \(k_{\text{L}} a\) mass transfer was estimated to be 34 times higher than the conventional Rushton Turbine set-up. Notably, the impeller power consumption was modeled to be about 50 % lower. Independent \(k_{\text{L}} a\) measurements applying the same operational conditions confirmed this finding. Motivated by these simulated and experimental results, the new aeration and stirring device is qualified as a very promising tool especially useful for cell culture applications which are characterized by the challenging problem of achieving relatively high mass transfer conditions while inserting only low stirrer energy.

  • Modeling of gas–liquid mass transfer in a stirred tank bioreactor agitated by a Rushton Turbine or a new pitched blade impeller
    Bioprocess and Biosystems Engineering, 2013
    Co-Authors: Ricardo Gelves, A. Dietrich, Ralf Takors
    Abstract:

    A combined computational fluid dynamics (CFD) and population balance model (PBM) approach has been applied to simulate hydrodynamics and mass transfer in a 0.18 m3 gas–liquid stirred bioreactor agitated by (1) a Rushton Turbine, and (2) a new pitched blade geometry with rotating cartridges. The operating conditions chosen were motivated by typical settings used for culturing mammalian cells. The effects of turbulence, rotating flow, bubbles breakage and coalescence were simulated using the k–e, multiple reference frame (MRF), Sliding mesh (SM) and PBM approaches, respectively. Considering the new pitched blade geometry with rotating aeration microspargers, \(k_{\text{L}} a\) mass transfer was estimated to be 34 times higher than the conventional Rushton Turbine set-up. Notably, the impeller power consumption was modeled to be about 50 % lower. Independent \(k_{\text{L}} a\) measurements applying the same operational conditions confirmed this finding. Motivated by these simulated and experimental results, the new aeration and stirring device is qualified as a very promising tool especially useful for cell culture applications which are characterized by the challenging problem of achieving relatively high mass transfer conditions while inserting only low stirrer energy.