scholarly journals Modeling of mixing in stirred bioreactors 4. mixing time for aerated bacteria, yeasts and fungus broths

2004 ◽  
Vol 58 (3) ◽  
pp. 128-137 ◽  
Author(s):  
Dan Cascaval ◽  
Anca-Irina Galaction ◽  
Corneliu Oniscu ◽  
Florina Ungureanu
Keyword(s):  
Experimental Data ◽  
Mixing Time ◽  
Biomass Concentration ◽  
Aeration Rate ◽  
Mixing Efficiency ◽  
Complex Flow ◽  
Average Deviation ◽  
Stirred Bioreactors ◽  
Turbine Impeller ◽  
Good Agreement

The mixing time for bioreactors depends mainly on the rheoiogicai properties of the broths, the biomass concentration and morphology, mixing system characteristics and fermentation conditions. For quantifying the influence of these factors on the mixing efficiency for stirred bioreactors, aerated broths of bacteria (P. shermanii), yeasts (S. cerevisiae) and fungi (P. chrysogenum, free mycelia and mycelial aggregates) of different concentrations have been investigated using a laboratory bioreactor with a double turbine impeller. The experimental data indicated that the influence of the rotation speed, aeration rate and stirrer positions on the mixing intensity strongly differ from one system to another and must be correlated with the microorganism characteristics, namely: the biomass concentration and morphology. Moreover, compared with non-aerated broths, variations of the mixing time with the considered parameters are very different, due to the complex flow mechanism of gas-liquid dispersions. By means of the experimental data and using a multiregression analysis method some mathematical correlations for the mixing time of the general form: tm = a1*Cx2+a2*Cx+a3*IgVa+a4-N2+a5-N+a6/a7*L2+a8*L+a9 were established. The proposed equations offer good agreement with the experiments, the average deviation being ?6.7% - ?9.4 and are adequate for the flow regime Re < 25,000.

scholarly journals Modeling of mixing for stirred bioreactors: 3. Mixing time for aerated simulated broths

2002 ◽  
Vol 56 (12) ◽  
pp. 506-513 ◽  
Author(s):  
Dan Cascaval ◽  
Corneliu Oniscu ◽  
Anca-Irina Galaction ◽  
Fiorina Ungureanu
Keyword(s):  
Flow Rate ◽  
Rotation Speed ◽  
Mixing Time ◽  
Volumetric Flow Rate ◽  
Mixing Efficiency ◽  
Complex Flow ◽  
Average Deviation ◽  
Stirred Bioreactor ◽  
Stirred Bioreactors ◽  
Turbine Impeller

This paper presents the experiments on mixing efficiency for aerated media for a laboratory stirred bioreactor with a double turbine impeller. The effects of stirrer rotation speed, air volumetric flow rate and stirrer position on the shaft on mixing time for aerated water and simulated broths (CMCNa solutions) were analyzed. Compared to non-aerated broths, the results indicated that the variation of mixing time with the considered parameters is very different, due to the complex flow mechanism of the gas-liquid dispersion, a mechanism which is changed by changing the broth properties or fermentation conditions. Using the Statistics Toolbox of MATLAB some correlations between the mixing time and rotation speed, air volumetric flow rate and stirrer position on the shaft were established. The proposed equations agree well with the experiments, the average deviation being ?9.02%.

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).

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.

scholarly journals Numerical Investigation of Impeller-Vaned Diffuser Interaction in a Centrifugal Compressor

2019 ◽  
Vol 9 (8) ◽  
pp. 1619 ◽  
Author(s):  
Matteo Bardelli ◽  
Carlo Cravero ◽  
Martino Marini ◽  
Davide Marsano ◽  
Omar Milingi
Keyword(s):  
Experimental Data ◽  
Centrifugal Compressor ◽  
Complex Flow ◽  
Vaned Diffuser ◽  
Working Zone ◽  
Cfd Models ◽  
Set Up ◽  
Operating Points ◽  
Experimental Reference ◽  
Good Agreement

The work presents the results of a CFD campaign to investigate the impeller–diffuser interaction in a centrifugal compressor, taking advantage of experimental data from the open literature. Previous studies on the same turbomachine focused on an experimental investigation to understand the flow interaction between the impeller and the vaned diffuser. These experimental data have been used to validate the simulation approach and discuss its results. Several CFD models with increasing complexity have been developed to take into account different aspects. The steady analysis has been performed to highlight the potentials and limitations of such models and to carry out a first study of the flow. In order to analyze the impeller–diffuser interaction, a further model for the unsteady analysis has been set up. Two different operating points have been investigated: one on the surge limit and another in a more stable working zone. A good agreement with the experimental reference data has been obtained with the unsteady analysis and some insights in the complex flow field are deduced.

scholarly journals Charge-exchange isobaric resonances

2018 ◽  
Vol 194 ◽  
pp. 02009 ◽  
Author(s):  
Yu.S. Lutostansky
Keyword(s):  
Experimental Data ◽  
Charge Exchange ◽  
Cross Sections ◽  
Microscopic Theory ◽  
Average Deviation ◽  
Resonance Energies ◽  
Strength Functions ◽  
Experimental Values ◽  
Gamow Teller ◽  
Good Agreement

Three types of the charge-exchange isobaric resonances - giant Gamow-Teller (GTR), the analog (AR) and pygmy (PR) ones are investigated using the microscopic theory of finite Fermi systems and its approximated version. The calculated energies of GTR, AR and three PR’s are in good agreement with the experimental data. Calculated differences ΔEG-A=EGTR-EAR go to zero in heavier nuclei indicating the restoration of Wigner SU(4)-symmetry. The average deviation for ΔEG-A is 0.30 MeV for the 33 considered nuclei where experimental data are available. The comparison of calculations with experimental data on the energies of charge-exchange pygmy resonances gives the standard deviation δE<0:40 MeV. Strength functions for the 118Sn, 71Ga, 98Mo and 127I isotopes are calculated and the calculated resonance energies and amplitudes of the resonance peaks are close to the experimental values. Strong influence of the charge-exchange resonances on neutrino capturing cross sections is demonstrated.

scholarly journals Optimization of mixing in stirred bioreactors, 2: Selection of optimum impeller combinations for non-aerated simulated broths

2007 ◽  
Vol 13 (1) ◽  
pp. 21-26 ◽  
Author(s):  
Anca-Irina Galaction ◽  
Elena Folescu ◽  
Dan Cascaval
Keyword(s):  
Fermentation Broth ◽  
Mixing Time ◽  
Maximum Level ◽  
Specific Power ◽  
Mixing Efficiency ◽  
Mechanical Mixing ◽  
Rushton Turbine ◽  
Shear Effects ◽  
Stirred Bioreactors ◽  
Selection Of

Although radial impellers, especially the Rushton turbine, are widely used in stirred bioreactors, their applicability is limited by the high apparent viscosities of the broths. For optimizing mechanical mixing by selecting the appropriate impeller for a specific fermentation broth or process, the comparative analysis of the mixing efficiency, energy costs and shear effects on the biocatalysts is required. By means of this analysis, three different combinations of radial impellers for water and viscous simulated broths were selected for attaining optimum mixing in a bioreactor. The proposed impellers combinations offer the most intense and uniformly distributed mixing and the lowest specific power consumption required for reaching a maximum level of mixing time of less than one minute.

Direct Simulation of Double-Diffusive Layered Convection

1995 ◽  
Vol 117 (2) ◽  
pp. 334-339 ◽  
Author(s):  
M. T. Hyun ◽  
T. L. Bergman
Keyword(s):  
Experimental Data ◽  
Rayleigh Number ◽  
Mixing Time ◽  
Direct Simulation ◽  
Lateral Heating ◽  
Physical Mechanisms ◽  
Heating And Cooling ◽  
Buoyancy Ratio ◽  
Double Diffusive ◽  
Good Agreement

A two-layer, salt-stratified system destabilized and mixed by lateral heating and cooling is simulated numerically using a spectral methodology. As noted in previous studies, the mixing time is delayed as the stabilizing buoyancy ratio increases, and as the Rayleigh number decreases. Depending on the regime of operation, however, distinct physical mechanisms are responsible for interface erosion and system mixing. At low Ra, erosion is gradual with overlying (underlying) fluid sheared from the interface and mixed into the adjacent thermally convecting layer. At high Ra, an intermittent mechanism is predicted to occur with solutally distinct plumes bombarding the interface and ejecting fluid into the convecting layers. Predictions obtained with the spectral method are in relatively good agreement with experimental data.

scholarly journals Influence of Sparger Type and Regime of Fluid on Biomass and Lipid Productivity of Chlorella vulgaris Culture in a Pilot Airlift Photobioreactor

2019 ◽  
Vol 33 (1) ◽  
pp. 87-98 ◽  
Author(s):  
Yaremi Lopez-Hernandez ◽  
Carlos Orozco ◽  
Ines Garcia-Peña ◽  
Jorge Ramirez-Muñoz ◽  
Luis Torres
Keyword(s):  
Flow Rate ◽  
Chlorella Vulgaris ◽  
Mixing Time ◽  
Air Flow ◽  
Lipid Production ◽  
Biomass Concentration ◽  
Inverse Correlation ◽  
Aeration Rate ◽  
Air Flow Rate ◽  
Lipid Concentration

The effect of different types of spargers and the influence of the air flow rate on biomass and lipids production by Chlorella vulgaris was evaluated. These data allowed correlation of the hydrodynamic behavior of the photobioreactor with the byproducts production. The hydrodynamic characterization was developed by determining the mixing time (tM), hold-up, and total volumetric mass transfer coefficient of CO2, kLa(CO2)T, at increasing air flow rates for three different spargers: star-shaped, cross-shaped and porous glass surface sparger. The hydrodynamic characterization showed that the tM decreased, while the hold-up values and the kLa(CO2)T increased as a result of the increment in the volumetric air flow rate between 5 to 17 L min–1. The highest biomass and lipid concentrations were determined at the higher aeration rate (20 L min–1), which was correlated with the lower tM, the higher hold-up and kLa(CO2)T values. Biomass and lipid production showed an inverse correlation. The highest biomass concentration (750 mg L–1) and the lowest lipid concentration (10 mg L–1) were measured with the star sparger. In contrast, when the lowest biomass concentration was obtained (240 mg L–1), the highest lipid concentration of 196 mg L–1 was measured with the glass sparger. The maximum biomass productivity values were determined at the lower aeration rate and the star sparger, with the minimum power per unit of volume, which could be useful for a cost-effective process.

Energy Levels and Electromagnetic Transition of 90-94mo Nuclei Using Ibm-1

2020 ◽  
pp. 149-152
Keyword(s):  
Experimental Data ◽  
Transition Probability ◽  
Energy Levels ◽  
Dynamical Symmetry ◽  
Interacting Boson Model ◽  
Excitation Energies ◽  
Electromagnetic Transition ◽  
Boson Model ◽  
Energy States ◽  
Good Agreement

The energy states for the J , b , ɤ bands and electromagnetic transitions B (E2) values for even – even molybdenum 90 – 94 Mo nuclei are calculated in the present work of "the interacting boson model (IBM-1)" . The parameters of the equation of IBM-1 Hamiltonian are determined which yield the best excellent suit the experimental energy states . The positive parity of energy states are obtained by using IBS1. for program for even 90 – 94 Mo isotopes with bosons number 5 , 4 and 5 respectively. The" reduced transition probability B(E2)" of these neuclei are calculated and compared with the experimental data . The ratio of the excitation energies of the 41+ to 21+ states ( R4/2) are also calculated . The calculated and experimental (R4/2) values showed that the 90 – 94 Mo nuclei have the vibrational dynamical symmetry U(5). Good agreement was found from comparison between the calculated energy states and electric quadruple probabilities B(E2) transition of the 90–94Mo isotopes with the experimental data .

Predicting the Effect of Tire Tread Pattern Design on Thick Film Wet Traction

1977 ◽  
Vol 5 (1) ◽  
pp. 6-28 ◽  
Author(s):  
A. L. Browne
Keyword(s):  
Experimental Data ◽  
Network Design ◽  
Thick Film ◽  
Digital Computer ◽  
Analytical Tool ◽  
Design Practice ◽  
Pattern Design ◽  
Performance Results ◽  
Good Agreement

Abstract An analytical tool is presented for the prediction of the effects of changes in tread pattern design on thick film wet traction performance. Results are reported for studies in which the analysis, implemented on a digital computer, was used to determine the effect of different tread geometry features, among these being the number, width, and lateral spacing of longitudinal grooves and the angle of zigzags in longitudinal grooves, on thick film wet traction. These results are shown to be in good agreement with experimental data appearing in the literature and are used to formulate guidelines for tread groove network design practice.

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