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Joel Bertrand - One of the best experts on this subject based on the ideXlab platform.
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simulation of Flow generated by an axial Flow Impeller batch and continuous operation
Chemical Engineering Research & Design, 2004Co-Authors: A R Khopkar, P Mavros, Vivek V Ranade, Joel BertrandAbstract:It is important to extend and to validate computational Flow models to simulate continuous operation of stirred vessels and to capture possible interaction of feed inlet/outlet with the Flow generated by Impellers. In the present work, we have developed and used a computational model to understand the Flow generated by an axial Flow Impeller in a batch and a continuously operated baffled vessel. A multiple reference frames approach was used to simulate Flow generated by the Mixel TT Impeller in stirred vessel. The predicted velocity results show reasonably good agreement (qualitative as well as quantitative) with the experimental data. Characteristics of Flow around blades of Mixel TT were studied using the computational model. The computational model was extended to simulate Flow and mixing in a continuous operation. Simulations were carried out to understand the interaction of the jet emanating from the feed pipe and the Flow generated by the Impeller. Model predictions were compared with published experimental data, obtained by laser Doppler velocimetry. The differences and similarities between batch and continuous operation are highlighted. Mixing simulations were carried out to examine possible short-circuiting and non-ideal behaviour of the continuous operation of the stirred vessel. Influence of the Impeller speed, feed rate and location of inlet/outlet on mixing and on the extent of non-ideality of Flow was studied. The computational model and results discussed in this work will be useful for understanding the mixing process in continuous-Flow stirred vessels.
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piv measurements of Flow in an aerated tank stirred by a down and an up pumping axial Flow Impeller
Experimental Thermal and Fluid Science, 2004Co-Authors: Joel Bertrand, Joelle Aubin, Le N Sauze, David F Fletcher, Catherine XuerebAbstract:Abstract Liquid phase hydrodynamics in an aerated tank stirred by a down- and an up-pumping pitched blade turbine have been investigated using particle image velocimetry. The effect of agitator configuration and the gas phase on the mean velocity fields and turbulent quantities in the vessel have been investigated. The global mean gas holdup has also been evaluated for the two pumping conditions. For the gas Flow rate used, the presence of gas only slightly alters the liquid Flow patterns produced by both the down- and up-pumping configurations and causes a general decrease in the mean liquid velocities. The turbulent kinetic energy in the Impeller discharge region was not affected by the presence of gas, but in the bulk of the tank, aeration caused a decrease in this value. Global gas holdup was found to be ∼36% greater for the up-pumping Impeller and a large amount of gas was found to be entrained by the primary circulation loop.
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investigation by laser doppler velocimetry of the effects of liquid Flow rates and feed positions on the Flow patterns induced in a stirred tank by an axial Flow Impeller
Chemical Engineering Science, 2002Co-Authors: Paul Mavros, Ivan Fořt, Catherine Xuereb, Joel BertrandAbstract:The (ow patterns established in a continuously-fed stirred tank, equipped with a Mixel TT axial-(ow Impeller, have been investigated bylaser Doppler velocimetry , for a high and a low value of mean residence time—mixing time ratio. The pseudo-two-dimensional axial– radial-velocityvector plots, as well as the spatial distributions of the tangential velocitycomponent and the velocitypro;les around the Impeller, show that the interaction between the incoming liquid and the liquid entrained bythe agitator rotation cause the (ow pattern in the vessel to become stronglythree-dimensional, especiallyin the region between the plane, where the feeding tube lies, and the 180 ◦ -downstream plane. The increase in the liquid (ow rate and the location of the feed entryboth a$ect the (ow pattern, with the latter having a more pronounced e$ect. The overall process, in this mode of operation, depends upon the appropriate con;guration and choice of parameters: for conditions corresponding to high liquid (ow rates, the (ow patterns indicate the possibilityof short-circuiting, when the liquid is fed into the stream being drawn bythe agitator and when the outlet is located at the bottom of the vessel. ? 2002 Elsevier Science Ltd. All rights reserved.
A W Nienow - One of the best experts on this subject based on the ideXlab platform.
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suspension of microcarriers for cell culture with axial Flow Impellers
Chemical Engineering Research & Design, 2004Co-Authors: Shaliza Ibrahim, A W NienowAbstract:The suspension characteristics, the agitator speed, Njs, and the mean specific energy dissipation rate, (@eTjs, required to just fully suspend ∼20% wet weight Cytodex 3® microcarrier beads have been studied using a range of different diameter Chemineer HE-3 hydrofoils, a pair of Ekato InterMIG Impellers and a six-blade mixed-Flow Impeller in a baffled vessel of 19.2 1 operating volume containing phosphate buffer saline solution. Flat and modified tank bases were used. Njs values were observed to be in the range of 50 to 90 rev min-1. The use of Zwietering's correlation using existing literature geometric suspension parameters, S, to predict Njs would give values up to 50% higher. The low Njs values obtained in the experiments are attributed to the very small particle-liquid density difference (40 kg m-3), which eased the lifting of the particles from the tank bottom, compared to those studied previously. Also, it was found that at Njs, it took up to about 40 min to suspend all particles as the upper surface of the initially settled bed was scoured away. Previous work has not reported such a long-term phenomenon. With the liquid/particle properties used in this study, the three-blade hydrofoil HE-3 Impeller of D/T = 0.39 in a cone-and-fillet based tank was marginally the most efficient; that is, it had the lowest (@eT)js of ∼0.5 × 10-3 W kg-1. However, (@eT)js was less than 1 × 10-3 W kg-1 in most cases with the different size HE-3 hydrofoils, which implies that these geometries would probably be suitable for application in shear-sensitive animal cell culture systems using such microcarriers. © 2004 Institution of Chemical Engineers.
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suspension of microcarriers for cell culture with axial Flow Impellers
Chemical Engineering Research & Design, 2004Co-Authors: Shaliza Ibrahim, A W NienowAbstract:The suspension characteristics, the agitator speed, Njs, and the mean specific energy dissipation rate, ( e ¯ T )js, required to just fully suspend ∼20% wet weight Cytodex 3® microcarrier beads have been studied using a range of different diameter Chemineer HE-3 hydrofoils, a pair of Ekato InterMIG Impellers and a six-blade mixed-Flow Impeller in a baffled vessel of 19.2 l operating volume containing phosphate buffer saline solution. Flat and modified tank bases were used. Njs values were observed to be in the range of 50 to 90 rev min−1. The use of Zwietering's correlation using existing literature geometric suspension parameters, S, to predict Njs would give values up to 50% higher. The low Njs values obtained in the experiments are attributed to the very small particle–liquid density difference (40 kg m−3), which eased the lifting of the particles from the tank bottom, compared to those studied previously. Also, it was found that at Njs, it took up to about 40 min to suspend all particles as the upper surface of the initially settled bed was scoured away. Previous work has not reported such a long-term phenomenon. With the liquid/particle properties used in this study, the three-blade hydrofoil HE-3 Impeller of D/T = 0.39 in a cone-and-fillet based tank was marginally the most efficient; that is, it had the lowest ( e ¯ T )js of ∼0.5 x 10−3 W kg−1. However, ( e ¯ T )js was less than 1 x 10−3 Wkg−1 in most cases with the different size HE-3 hydrofoils, which implies that these geometries would probably be suitable for application in shear-sensitive animal cell culture systems using such microcarriers.
Catherine Xuereb - One of the best experts on this subject based on the ideXlab platform.
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piv measurements of Flow in an aerated tank stirred by a down and an up pumping axial Flow Impeller
Experimental Thermal and Fluid Science, 2004Co-Authors: Joel Bertrand, Joelle Aubin, Le N Sauze, David F Fletcher, Catherine XuerebAbstract:Abstract Liquid phase hydrodynamics in an aerated tank stirred by a down- and an up-pumping pitched blade turbine have been investigated using particle image velocimetry. The effect of agitator configuration and the gas phase on the mean velocity fields and turbulent quantities in the vessel have been investigated. The global mean gas holdup has also been evaluated for the two pumping conditions. For the gas Flow rate used, the presence of gas only slightly alters the liquid Flow patterns produced by both the down- and up-pumping configurations and causes a general decrease in the mean liquid velocities. The turbulent kinetic energy in the Impeller discharge region was not affected by the presence of gas, but in the bulk of the tank, aeration caused a decrease in this value. Global gas holdup was found to be ∼36% greater for the up-pumping Impeller and a large amount of gas was found to be entrained by the primary circulation loop.
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investigation by laser doppler velocimetry of the effects of liquid Flow rates and feed positions on the Flow patterns induced in a stirred tank by an axial Flow Impeller
Chemical Engineering Science, 2002Co-Authors: Paul Mavros, Ivan Fořt, Catherine Xuereb, Joel BertrandAbstract:The (ow patterns established in a continuously-fed stirred tank, equipped with a Mixel TT axial-(ow Impeller, have been investigated bylaser Doppler velocimetry , for a high and a low value of mean residence time—mixing time ratio. The pseudo-two-dimensional axial– radial-velocityvector plots, as well as the spatial distributions of the tangential velocitycomponent and the velocitypro;les around the Impeller, show that the interaction between the incoming liquid and the liquid entrained bythe agitator rotation cause the (ow pattern in the vessel to become stronglythree-dimensional, especiallyin the region between the plane, where the feeding tube lies, and the 180 ◦ -downstream plane. The increase in the liquid (ow rate and the location of the feed entryboth a$ect the (ow pattern, with the latter having a more pronounced e$ect. The overall process, in this mode of operation, depends upon the appropriate con;guration and choice of parameters: for conditions corresponding to high liquid (ow rates, the (ow patterns indicate the possibilityof short-circuiting, when the liquid is fed into the stream being drawn bythe agitator and when the outlet is located at the bottom of the vessel. ? 2002 Elsevier Science Ltd. All rights reserved.
Joelle Aubin - One of the best experts on this subject based on the ideXlab platform.
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piv measurements of Flow in an aerated tank stirred by a down and an up pumping axial Flow Impeller
Experimental Thermal and Fluid Science, 2004Co-Authors: Joel Bertrand, Joelle Aubin, Le N Sauze, David F Fletcher, Catherine XuerebAbstract:Abstract Liquid phase hydrodynamics in an aerated tank stirred by a down- and an up-pumping pitched blade turbine have been investigated using particle image velocimetry. The effect of agitator configuration and the gas phase on the mean velocity fields and turbulent quantities in the vessel have been investigated. The global mean gas holdup has also been evaluated for the two pumping conditions. For the gas Flow rate used, the presence of gas only slightly alters the liquid Flow patterns produced by both the down- and up-pumping configurations and causes a general decrease in the mean liquid velocities. The turbulent kinetic energy in the Impeller discharge region was not affected by the presence of gas, but in the bulk of the tank, aeration caused a decrease in this value. Global gas holdup was found to be ∼36% greater for the up-pumping Impeller and a large amount of gas was found to be entrained by the primary circulation loop.
Shaliza Ibrahim - One of the best experts on this subject based on the ideXlab platform.
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suspension of microcarriers for cell culture with axial Flow Impellers
Chemical Engineering Research & Design, 2004Co-Authors: Shaliza Ibrahim, A W NienowAbstract:The suspension characteristics, the agitator speed, Njs, and the mean specific energy dissipation rate, (@eTjs, required to just fully suspend ∼20% wet weight Cytodex 3® microcarrier beads have been studied using a range of different diameter Chemineer HE-3 hydrofoils, a pair of Ekato InterMIG Impellers and a six-blade mixed-Flow Impeller in a baffled vessel of 19.2 1 operating volume containing phosphate buffer saline solution. Flat and modified tank bases were used. Njs values were observed to be in the range of 50 to 90 rev min-1. The use of Zwietering's correlation using existing literature geometric suspension parameters, S, to predict Njs would give values up to 50% higher. The low Njs values obtained in the experiments are attributed to the very small particle-liquid density difference (40 kg m-3), which eased the lifting of the particles from the tank bottom, compared to those studied previously. Also, it was found that at Njs, it took up to about 40 min to suspend all particles as the upper surface of the initially settled bed was scoured away. Previous work has not reported such a long-term phenomenon. With the liquid/particle properties used in this study, the three-blade hydrofoil HE-3 Impeller of D/T = 0.39 in a cone-and-fillet based tank was marginally the most efficient; that is, it had the lowest (@eT)js of ∼0.5 × 10-3 W kg-1. However, (@eT)js was less than 1 × 10-3 W kg-1 in most cases with the different size HE-3 hydrofoils, which implies that these geometries would probably be suitable for application in shear-sensitive animal cell culture systems using such microcarriers. © 2004 Institution of Chemical Engineers.
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suspension of microcarriers for cell culture with axial Flow Impellers
Chemical Engineering Research & Design, 2004Co-Authors: Shaliza Ibrahim, A W NienowAbstract:The suspension characteristics, the agitator speed, Njs, and the mean specific energy dissipation rate, ( e ¯ T )js, required to just fully suspend ∼20% wet weight Cytodex 3® microcarrier beads have been studied using a range of different diameter Chemineer HE-3 hydrofoils, a pair of Ekato InterMIG Impellers and a six-blade mixed-Flow Impeller in a baffled vessel of 19.2 l operating volume containing phosphate buffer saline solution. Flat and modified tank bases were used. Njs values were observed to be in the range of 50 to 90 rev min−1. The use of Zwietering's correlation using existing literature geometric suspension parameters, S, to predict Njs would give values up to 50% higher. The low Njs values obtained in the experiments are attributed to the very small particle–liquid density difference (40 kg m−3), which eased the lifting of the particles from the tank bottom, compared to those studied previously. Also, it was found that at Njs, it took up to about 40 min to suspend all particles as the upper surface of the initially settled bed was scoured away. Previous work has not reported such a long-term phenomenon. With the liquid/particle properties used in this study, the three-blade hydrofoil HE-3 Impeller of D/T = 0.39 in a cone-and-fillet based tank was marginally the most efficient; that is, it had the lowest ( e ¯ T )js of ∼0.5 x 10−3 W kg−1. However, ( e ¯ T )js was less than 1 x 10−3 Wkg−1 in most cases with the different size HE-3 hydrofoils, which implies that these geometries would probably be suitable for application in shear-sensitive animal cell culture systems using such microcarriers.