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 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 CFD Modelling of Global Mixing Parameters in a Peirce-Smith Converter with Comparison to Physical Modelling

2011 ◽  
Vol 6 (1) ◽  
Author(s):  
Deside K Chibwe ◽  
Guven Akdogan ◽  
Chris Aldrich ◽  
Rauf H Eric
Keyword(s):  
Flow Rate ◽  
Volume Fraction ◽  
Mixing Time ◽  
Volumetric Flow Rate ◽  
Numerical Code ◽  
Mixing Efficiency ◽  
Phase System ◽  
Cfd Modelling ◽  
Cold Model ◽  
Peirce Smith Converter

The flow pattern and mixing in an industrial Peirce-Smith converter (PSC) has been experimentally and numerically studied using cold model simulations. The effects of air volumetric flow rate and presence of overlaying slag phase on matte on the flow structure and mixing were investigated. The 2-D and 3-D simulations of the three phase system were carried out using volume of fluid (VOF) and realizable k - ɛ turbulence model to account for the multiphase and turbulence nature of the flow respectively. These models were implemented using commercial Computational Fluid Dynamics (CFD) numerical code FLUENT. The cold model for physical simulations was a 1:5 horizontal cylindrical container made of Perspex with seven tuyeres on one side of the cylinder typifying a Peirce-Smith converter. Compressed air was blown into the cylinder through the tuyeres, simulating air or oxygen enriched air injection into the PSC. The matte and slag phases were simulated with water and kerosene respectively in this study. The influence of varying blowing conditions and simulated slag quantities on the bulk mixing was studied with five different air volumetric flow rates and five levels of simulated slag thickness. Mixing time results were evaluated in terms of total specific mixing power and two mixing time correlations were proposed for estimating mixing times in the model of PSC for low slag and high slag volumes. Both numerical and experimental simulations were in good agreement to predict the variation characteristics of the system in relation to global flow field variables set up in the converter through mathematical calculation of relevant integrated quantities of turbulence, Volume Fraction (VF) and velocity magnitudes. The findings revealed that both air volumetric flow rate and presence of the overlaying slag layer have profound effects on the mixing efficiency of the converter.

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.

Fabrication of Microfluidic Rapid Micromixer

2011 ◽  
Vol 467-469 ◽  
pp. 2013-2017
Author(s):  
Hsiang Chen Hsu ◽  
Hsi Chien Liu ◽  
Cheng Jiun Han
Keyword(s):  
Flow Rate ◽  
Fluid Velocity ◽  
Volumetric Flow Rate ◽  
Mixing Efficiency ◽  
Mixing Index ◽  
Micro Pump ◽  
Chaotic Convection ◽  
Wide Range ◽  
Parametric Studies ◽  
Junction Type

A microfluidic multi-cylindric rapid micromixer is fabricated in the present paper. The key features in the presented MEMS-based microchannel design are (1) micro pump (2) Y-junction type channel (3) cylindric obstacle (4) notch with the edge of sharp teeth. Two different fluids (DI water and red ink) were pumped and injected into Y-type channel, and the fluids were broken-up by a cylindric obstacle in the center of tapered microchannel. The chaotic convection occurs in the mixing channel behind the cylindric obstacle. The mixing index is defined to qualify the mixing efficiency, which demonstrates the outlet notch with sharp teeth along the sidewall plays an important role for mixing effects. The developed micromixer can enhance mixing using the mechanisms of diffusion and convection for wide range of Reynolds number (0.01<Re<100). Parametric studies for volumetric flow rate include the number of cylindric obstacles, the number of notches with sharp-teeth and the width of microchannel. Preliminary results demonstrate that the mixing index reaches the desired effect (<0.1) within 0.08 second when the inlet fluid velocity is 0.49992m/s, i.e. volumetric flow rate is 1200μl /min. The presented device is faster than most of reported micromixers.

Multieffects on Mixing Quality of an Active Micromixer

2007 ◽  
Author(s):  
Thien X. Dinh ◽  
Yoshifumi Ogami
Keyword(s):  
Flow Rate ◽  
Pressure Loss ◽  
Rotation Speed ◽  
Mixing Efficiency ◽  
Mean Velocity ◽  
Mixing Performance ◽  
Convective Mixing ◽  
Wide Range ◽  
Computational Fluid Dynamics Cfd

The convective mixing performance of an active micromixer is analyzed by using computational fluid dynamics (CFD). The mixer consists of a Y-shaped channel and an N-paddle (3, 4, and 5) rotor with radius R suspended in the junction of the channel. Numerical simulations are performed for a wide range of rotation speed of the rotor, ω, and mean velocity in the mixer, U. The asymptotic mixing performance is investigated by means of Lagrangian particle tracking simulation, stretching of a material line, dispersive and distributive mixing efficiencies. The results show that the mixing performance depends on the combined variable ωR/U, whereas paddle number has ignorable effects. Physically, the convective ratio of rotation speed to mean velocity governs the mixing process in the mixer. Contrastively, paddle number affects significantly to pressure loss and fluid torque exercising on the rotor. The time-averaged fluid torque depends linearly on rotation speed regardless of flow rate. Pressure loss relates linearly to flow rate, negligibly to rotation speed. It shows that a smaller paddle number produces lesser pressure loss and fluid torque for the same mixing efficiency.

scholarly journals An Experimental and Simulated Study on Gas-Liquid Flow and Mixing Behavior in an ISASMELT Furnace

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 565 ◽  
Author(s):  
Hongliang Zhao ◽  
Tingting Lu ◽  
Pan Yin ◽  
Liangzhao Mu ◽  
Fengqin Liu
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Turbulent Viscosity ◽  
Mixing Time ◽  
Water Model ◽  
Mixing Efficiency ◽  
Gas Flow Rate ◽  
Factors Affecting ◽  
Sufficient Energy ◽  
Gas Liquid Flow

In this study, a water-model experiment and numerical simulation were carried out in a pilot ISASMELT furnace to study the factors affecting mixing time. The experimental results were compared to the simulation results to test the accuracy of the latter. To study the internal factors that affect the mixing time, the turbulent viscosity and flow field were calculated using simulation. In addition, following previous research, external factors that influence the mixing time including the depth of the submerged lance, lance diameter, gas flow rate, and the presence of a swirler were studied to investigate their effect on the flow regime. The results indicated that the mixing time is controlled by the turbulent viscosity and velocity vector. In addition, it was found that the lance diameter should not exceed 3.55 cm to maintain sufficient energy for stirring the bath. Finally, the optimal gas flow rate that offers the best mixing efficiency was found to be 50 Nm3/h.

Hydrodynamics of Stirred Bioreactors

1998 ◽  
Vol 51 (1) ◽  
pp. 3-32 ◽  
Author(s):  
A. W. Nienow
Keyword(s):  
Energy Dissipation ◽  
Mixing Time ◽  
Scale Up ◽  
Axial Flow ◽  
High Viscosity ◽  
Flow Patterns ◽  
Rushton Turbine ◽  
Stirred Bioreactor ◽  
Power Characteristics ◽  
Stirred Bioreactors

This review of the hydrodynamics of stirred bioreactors begins with an introduction to the agitation problems of particular concern in such systems. This is followed by a brief review of some basic concepts in turbulence and rheology of relevance to bioreactors. Important aspects of single phase mixing in low viscosity, high viscosity and Theologically complex broths are then covered in some detail including flow patterns, power number versus Reynolds number plots (including the modification of the latter to allow for shear thinning broths), flow numbers, energy dissipation rates and flow close to impellers and between multiple impeller systems. From these basic principles, the problem of homogenization is then covered in depth because of its significance for bioreactor performance. Aeration concepts are then introduced and the behavior of traditional Rushton turbine impellers is then treated in detail, covering the flow patterns, aerated power characteristics, mixing time and scale-up considerations. The weaknesses of the Rushton turbine are then discussed which leads into a section describing how more modern impellers are able to improve on many of these, especially emphasising their ability to introduce more energy dissipation into the broth and handle more air before flooding, both of which enhance oxygen transfer. The improvement in bulk blending found with multiple axial flow agitators is brought out too. Finally, the retrofitting of fermenters originally containing Rushton turbines with these more modern impellers is discussed. In conclusion, it is clear that there have been substantial increases in the understanding of stirred bioreactor hydrodynamics. However, whilst further understanding will occur within the framework discussed here, the expectation must be that computational fluid dynamics will increase in importance in spite of the difficulty of handling complex rheology, multiphase systems and biological responses. This review article has 135 references.

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.

scholarly journals Performance analysis of a ball valve used for gas pipelines by introducing nondimensional parameters

2019 ◽  
Vol 11 (1) ◽  
pp. 168781401882335 ◽  
Author(s):  
Chul-Kyu Kim ◽  
Sang-Moon Lee ◽  
Choon-Man Jang
Keyword(s):  
Flow Rate ◽  
Rate Ratio ◽  
Pressure Ratio ◽  
Volumetric Flow Rate ◽  
Ball Valve ◽  
Flow Coefficient ◽  
Flow Rate Ratio ◽  
Complex Flow ◽  
Valve Size ◽  
Mass Flow Rate Ratio

The present study deals with the performance characteristics of a ball valve used for gas pipelines by introducing nondimensional parameters. The ball valve has relatively complex flow characteristics on the inside and downstream of the valve, although it has a simple structure as compared with the other valves. The nondimensional parameters, which define the valve operating conditions, are introduced to analyze the nature of the physical properties due to the valve’s complex flow. To define the valve flow conditions with respect to valve size, seven nondimensional parameters were selected: pressure ratio, volumetric flow rate ratio, mass flow rate ratio, Reynolds number, Mach number, valve flow coefficient, and inherent flow coefficient. The open-loop type experimental setup is designed to measure the pressure drop and the volumetric flow rate of the ball valve according to the opening rate (angle) of the test valve. Based on the experimental data, obtained by the data acquisition system of the test rig, useful nondimensional parameters to define the nature of the valve performance have been selected and determined. Throughout the experimental analysis of the ball valve, it was found that the nondimensional parameters of pressure ratio, Reynolds number, and Mach number have a similar tendency as related to the valve performance. It can be seen that the intrinsic characteristics of the ball valve are represented by the selected nondimensional parameters, which are defined irrespective of the valve size. The authors proposed a quadratic polynomial for the volumetric flow rate ratio, and the mass flow rate ratio, and introduced the formula for predicting the inherent flow coefficient by the cubic approximation polynomial. It is noted that the nondimensional parameters of the ball valve can be used to determine the performance characteristics with respect to the valve-opening rate and size effectively.

Treatment of wastewater containing o-phenylenediamine by ozone in a rotor-stator reactor

2015 ◽  
Vol 73 (6) ◽  
pp. 1357-1363 ◽  
Author(s):  
Moses Arowo ◽  
Yingwen Li ◽  
Guangwen Chu ◽  
Baochang Sun ◽  
Jianfeng Chen ◽  
...  
Keyword(s):  
Removal Efficiency ◽  
Flow Rate ◽  
Ozone Concentration ◽  
Rotation Speed ◽  
Oxygen Demand ◽  
Volumetric Flow Rate ◽  
Degradation Process ◽  
Promising Alternative ◽  
Cod Reduction ◽  
Pre Treatment

This work employed a novel rotor-stator reactor (RSR) to intensify the degradation process of o-phenylenediamine (o-PDA) by ozone. The effects of different operating parameters including initial pH, temperature, rotation speed, liquid volumetric flow rate and inlet ozone concentration on the removal efficiency of o-PDA were investigated in an attempt to establish the optimum conditions. The removal efficiency was evaluated in terms of degradation ratio and chemical oxygen demand (COD) reduction ratio of the o-PDA wastewater. Results indicate that the removal efficiency decreased with increasing liquid volumetric flow rate but increased with an increase in pH and inlet ozone concentration. Also, the removal efficiency increased up to a certain level with an increase in rotation speed and temperature. Additionally, a comparison experiment was carried out in a stirred tank reactor (STR), and the results show that the degradation and COD reduction ratios reached a maximum of 94.6% and 61.2% in the RSR as compared to 45.3% and 28.6% in the STR, respectively. This work demonstrates that ozone oxidation carried out in RSR may be a promising alternative for pre-treatment of o-PDA wastewater.

Sign in / Sign up

Export Citation Format

Share Document