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J Jaap C Schouten - One of the best experts on this subject based on the ideXlab platform.
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effect of rotor stator distance and rotor radius on the rate of gas Liquid Mass Transfer in a rotor stator spinning disc reactor
Chemical Engineering and Processing, 2011Co-Authors: Marco M Meeuwse, John Van Der Schaaf, E F Hamming, J Jaap C SchoutenAbstract:Abstract This paper describes the effect of rotor radius, rotor–stator distance, Liquid flow rate and rotational disc speed on the rate of gas–Liquid Mass Transfer in a rotor–stator spinning disc reactor. A rotor radius of 0.135 m is studied with rotor–stator distances of 1, 2 and 5 mm, at rotational disc speeds up to 209 rad s−1, and compared with a rotor radius of 0.066 m. At rotational disc speeds lower than 70 rad s−1, elongated gas bubbles are formed, that are larger than the rotor–stator distance. At rotational disc speeds above 100 rad s−1, spherical gas bubbles are formed that are smaller than the rotor–stator distance. The volumetric gas–Liquid Mass Transfer coefficient increases with increasing rotational disc speed and decreases with increasing Liquid flow rate. This decrease is larger than predicted by the Wallis drift flux model because of the complex two-phase flow pattern. The rate of gas–Liquid Mass Transfer per unit of reactor volume increases with decreasing rotor–stator distance. The maximum observed volumetric Mass Transfer coefficient in case of the 0.135 m rotor is a factor 3 higher than in case of the 0.066 m rotor, while the rate of energy dissipation is a factor 15 higher.
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Mass Transfer in a rotor stator spinning disc reactor with co feeding of gas and Liquid
Industrial & Engineering Chemistry Research, 2010Co-Authors: Marco M Meeuwse, John Van Der Schaaf, J Jaap C SchoutenAbstract:This paper presents a new type of spinning disk reactor configuration for gas−Liquid operations. It combines the features of a classical spinning disk with a Liquid film on the rotor [e.g., Aoune, A.; Ramshaw, C. Int. J. Heat Mass Transfer 1999, 42, 2543−2556] and those of a rotor−stator spinning disk unit with a single gas inlet in the bottom stator [Meeuwse, M.; van der Schaaf, J.; Kuster, B. F. M.; Schouten, J. C. Chem. Eng. Sci. 2010, 65 (1), 466−471]. In this new configuration, gas and Liquid are cofed through an inlet in the top stator. It is shown that gas−Liquid Mass Transfer mainly takes place in the dispersed region between the rotor and the bottom stator. kGLaGLVR in this region is up to a factor of 6 larger than in the region with the Liquid film on the rotor. Simulation of gas desorption from a saturated Liquid shows that the gas−Liquid Mass Transfer in this cofed configuration is considerably improved in comparison to the separate reactors, at similar operating conditions. The new reactor ha...
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gas Liquid Mass Transfer in a rotor stator spinning disc reactor
Chemical Engineering Science, 2010Co-Authors: Van Der John J Schaaf, Marco M Meeuwse, Bfm Ben Kuster, J Jaap C SchoutenAbstract:Abstract This paper describes a new multiphase reactor, the rotor–stator spinning disc reactor, which shows high rates of gas–Liquid Mass Transfer in comparison to conventional multiphase reactors. The volumetric gas–Liquid Mass Transfer coefficient k GL a GL in the rotor–stator spinning disc reactor increases with increasing rotational disc speed, due to the higher surface renewal rate caused by the increasing turbulence, and with increasing gas flow rate. Measured k GL a GL values are as high as 0.43 m L 3 m R - 3 s - 1 at 7.3 × 10 - 6 m 3 s - 1 gas flow and a rotational disc speed of 179 rad s - 1 , and are expected to increase even further at increasing rotational disc speed. This is twice as high as for conventional reactors as bubble columns, in spite of the low gas holdup of 0.021 m G 3 m R - 3 with only one gas inlet. The volumetric Mass Transfer per unit volume of gas, k GL a GL / ɛ G , of 20.5 m L 3 m G - 3 s - 1 is 40 times higher than 0.5 m L 3 m G - 3 s - 1 for a bubble column.
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gas Liquid Mass Transfer in rotating solid foam reactors
Chemical Engineering Science, 2010Co-Authors: R Tschentscher, T A Nijhuis, J Van Der Schaaf, Bernhard Kuster, J Jaap C SchoutenAbstract:Abstract Three-phase reactor designs based on rotating solid foams for the application in the fine chemical industry are developed. The aim is to use solid foams both as a catalyst support and stirrer in order to mix the gas and Liquid phases and create fine gas bubbles. Gas–Liquid Mass Transfer data are presented for different solid foam stirrer configurations and compared to an optimized Rushton stirrer. Solid foam stirrers were developed in a blade and a block design. Both foam reactor designs work at stirring rates below 600 rpm. Using the foam blade design, gas bubbles are mainly created by the turbulence at the gas–Liquid interface. Large bubbles are broken up by the foam blades. Using a foam block design, rotation leads to the structurization of the reactor volume into sections strongly differing in gas holdup, flow behavior and bubble size distribution. This results in a gas–Liquid Mass Transfer, which is 50% higher than the Rushton stirrer used as comparison. The foam stirrer designs can be easily used in ordinary three-phase reactors and show a high potential for further optimization of the gas–Liquid flow pattern and therefore for further increase of the rate of Mass Transfer.
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influence of Liquid viscosity and surface tension on the gas Liquid Mass Transfer coefficient for solid foam packings in co current two phase flow
Chemical Engineering Research & Design, 2008Co-Authors: C.p. Stemmet, Van Der John J Schaaf, Bfm Ben Kuster, Frank F Bartelds, J Jaap C SchoutenAbstract:Abstract The gas–Liquid Mass Transfer coefficient and other hydrodynamic parameters such as Liquid holdup and frictional pressure drop are presented for gas and Liquid moving in co-current upflow and downflow through solid foam packings of 10 and of 40 pores per linear inch (ppi). The effect of increasing the Liquid viscosity on the Mass Transfer coefficient in co-current upflow is quantified and correlated to the frictional pressure drop, a measure of the frictional energy dissipation: k L a GL ɛ L ( S c L / S c water ) 0.69 = 2.05 × 1 0 − 4 P f 0.8 (mL3 mP−3 s−1). The gas–Liquid Mass Transfer coefficient in co-current downflow is correlated to the Liquid velocity and the Schmidt number using the correlation proposed by Sherwood and Holloway [Sherwood, T. and Holloway, F., 1940, Performance of packed towers—Liquid film data for several packings, Transactions of the American Institute of Chemical Engineers 36: 39–70]: k L a GL ɛ L D L − 1 = 3.7 ( u L ρ L μ L − 1 ) 1.16 ( S c L ) 0.5 (mL mP−3). The results for the gas–Liquid Mass Transfer coefficient in co-current upflow were correlated with a similar equation, where the influence of the gas velocity is included, similar to the correlations for packed beds of spherical particles proposed in Fukushima and Kusaka [Fukushima, S. and Kusaka, K., 1979, Gas–Liquid Mass Transfer and hydrodynamic flow region in packed columns with cocurrent upward flow, Journal of Chemical Engineering of Japan 12 (4): 296–301]: k L a GL ɛ L D L − 1 = 311 u G 0.44 ( u L ρ L μ L − 1 ) 0.92 ( S c L ) 0.5 (mL mP−3). In this study the Liquid Schmidt number dependency of the gas–Liquid Mass Transfer coefficient points to the penetration theory describing the rate of Mass Transfer for gas–Liquid flow through solid foam packings.
Marco M Meeuwse - One of the best experts on this subject based on the ideXlab platform.
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effect of rotor stator distance and rotor radius on the rate of gas Liquid Mass Transfer in a rotor stator spinning disc reactor
Chemical Engineering and Processing, 2011Co-Authors: Marco M Meeuwse, John Van Der Schaaf, E F Hamming, J Jaap C SchoutenAbstract:Abstract This paper describes the effect of rotor radius, rotor–stator distance, Liquid flow rate and rotational disc speed on the rate of gas–Liquid Mass Transfer in a rotor–stator spinning disc reactor. A rotor radius of 0.135 m is studied with rotor–stator distances of 1, 2 and 5 mm, at rotational disc speeds up to 209 rad s−1, and compared with a rotor radius of 0.066 m. At rotational disc speeds lower than 70 rad s−1, elongated gas bubbles are formed, that are larger than the rotor–stator distance. At rotational disc speeds above 100 rad s−1, spherical gas bubbles are formed that are smaller than the rotor–stator distance. The volumetric gas–Liquid Mass Transfer coefficient increases with increasing rotational disc speed and decreases with increasing Liquid flow rate. This decrease is larger than predicted by the Wallis drift flux model because of the complex two-phase flow pattern. The rate of gas–Liquid Mass Transfer per unit of reactor volume increases with decreasing rotor–stator distance. The maximum observed volumetric Mass Transfer coefficient in case of the 0.135 m rotor is a factor 3 higher than in case of the 0.066 m rotor, while the rate of energy dissipation is a factor 15 higher.
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Mass Transfer in a rotor stator spinning disc reactor with co feeding of gas and Liquid
Industrial & Engineering Chemistry Research, 2010Co-Authors: Marco M Meeuwse, John Van Der Schaaf, J Jaap C SchoutenAbstract:This paper presents a new type of spinning disk reactor configuration for gas−Liquid operations. It combines the features of a classical spinning disk with a Liquid film on the rotor [e.g., Aoune, A.; Ramshaw, C. Int. J. Heat Mass Transfer 1999, 42, 2543−2556] and those of a rotor−stator spinning disk unit with a single gas inlet in the bottom stator [Meeuwse, M.; van der Schaaf, J.; Kuster, B. F. M.; Schouten, J. C. Chem. Eng. Sci. 2010, 65 (1), 466−471]. In this new configuration, gas and Liquid are cofed through an inlet in the top stator. It is shown that gas−Liquid Mass Transfer mainly takes place in the dispersed region between the rotor and the bottom stator. kGLaGLVR in this region is up to a factor of 6 larger than in the region with the Liquid film on the rotor. Simulation of gas desorption from a saturated Liquid shows that the gas−Liquid Mass Transfer in this cofed configuration is considerably improved in comparison to the separate reactors, at similar operating conditions. The new reactor ha...
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gas Liquid Mass Transfer in a rotor stator spinning disc reactor
Chemical Engineering Science, 2010Co-Authors: Van Der John J Schaaf, Marco M Meeuwse, Bfm Ben Kuster, J Jaap C SchoutenAbstract:Abstract This paper describes a new multiphase reactor, the rotor–stator spinning disc reactor, which shows high rates of gas–Liquid Mass Transfer in comparison to conventional multiphase reactors. The volumetric gas–Liquid Mass Transfer coefficient k GL a GL in the rotor–stator spinning disc reactor increases with increasing rotational disc speed, due to the higher surface renewal rate caused by the increasing turbulence, and with increasing gas flow rate. Measured k GL a GL values are as high as 0.43 m L 3 m R - 3 s - 1 at 7.3 × 10 - 6 m 3 s - 1 gas flow and a rotational disc speed of 179 rad s - 1 , and are expected to increase even further at increasing rotational disc speed. This is twice as high as for conventional reactors as bubble columns, in spite of the low gas holdup of 0.021 m G 3 m R - 3 with only one gas inlet. The volumetric Mass Transfer per unit volume of gas, k GL a GL / ɛ G , of 20.5 m L 3 m G - 3 s - 1 is 40 times higher than 0.5 m L 3 m G - 3 s - 1 for a bubble column.
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gas Liquid Mass Transfer and axial dispersion in solid foam packings
Chemical Engineering Science, 2007Co-Authors: C.p. Stemmet, Van Der John J Schaaf, Marco M Meeuwse, Bfm Ben Kuster, J Jaap C SchoutenAbstract:The Mass Transfer coefficient and other hydrodynamic parameters are presented for a gas and Liquid (air–water system) moving in a co-current upflow configuration through solid foam packings in the range of 10–40 pores per linear inch (ppi). Axial dispersion in the Liquid has been excluded by observing that the Liquid was in plug flow in the range of superficial Liquid and gas velocities studied (0.02
Bfm Ben Kuster - One of the best experts on this subject based on the ideXlab platform.
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gas Liquid Mass Transfer in a rotor stator spinning disc reactor
Chemical Engineering Science, 2010Co-Authors: Van Der John J Schaaf, Marco M Meeuwse, Bfm Ben Kuster, J Jaap C SchoutenAbstract:Abstract This paper describes a new multiphase reactor, the rotor–stator spinning disc reactor, which shows high rates of gas–Liquid Mass Transfer in comparison to conventional multiphase reactors. The volumetric gas–Liquid Mass Transfer coefficient k GL a GL in the rotor–stator spinning disc reactor increases with increasing rotational disc speed, due to the higher surface renewal rate caused by the increasing turbulence, and with increasing gas flow rate. Measured k GL a GL values are as high as 0.43 m L 3 m R - 3 s - 1 at 7.3 × 10 - 6 m 3 s - 1 gas flow and a rotational disc speed of 179 rad s - 1 , and are expected to increase even further at increasing rotational disc speed. This is twice as high as for conventional reactors as bubble columns, in spite of the low gas holdup of 0.021 m G 3 m R - 3 with only one gas inlet. The volumetric Mass Transfer per unit volume of gas, k GL a GL / ɛ G , of 20.5 m L 3 m G - 3 s - 1 is 40 times higher than 0.5 m L 3 m G - 3 s - 1 for a bubble column.
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influence of Liquid viscosity and surface tension on the gas Liquid Mass Transfer coefficient for solid foam packings in co current two phase flow
Chemical Engineering Research & Design, 2008Co-Authors: C.p. Stemmet, Van Der John J Schaaf, Bfm Ben Kuster, Frank F Bartelds, J Jaap C SchoutenAbstract:Abstract The gas–Liquid Mass Transfer coefficient and other hydrodynamic parameters such as Liquid holdup and frictional pressure drop are presented for gas and Liquid moving in co-current upflow and downflow through solid foam packings of 10 and of 40 pores per linear inch (ppi). The effect of increasing the Liquid viscosity on the Mass Transfer coefficient in co-current upflow is quantified and correlated to the frictional pressure drop, a measure of the frictional energy dissipation: k L a GL ɛ L ( S c L / S c water ) 0.69 = 2.05 × 1 0 − 4 P f 0.8 (mL3 mP−3 s−1). The gas–Liquid Mass Transfer coefficient in co-current downflow is correlated to the Liquid velocity and the Schmidt number using the correlation proposed by Sherwood and Holloway [Sherwood, T. and Holloway, F., 1940, Performance of packed towers—Liquid film data for several packings, Transactions of the American Institute of Chemical Engineers 36: 39–70]: k L a GL ɛ L D L − 1 = 3.7 ( u L ρ L μ L − 1 ) 1.16 ( S c L ) 0.5 (mL mP−3). The results for the gas–Liquid Mass Transfer coefficient in co-current upflow were correlated with a similar equation, where the influence of the gas velocity is included, similar to the correlations for packed beds of spherical particles proposed in Fukushima and Kusaka [Fukushima, S. and Kusaka, K., 1979, Gas–Liquid Mass Transfer and hydrodynamic flow region in packed columns with cocurrent upward flow, Journal of Chemical Engineering of Japan 12 (4): 296–301]: k L a GL ɛ L D L − 1 = 311 u G 0.44 ( u L ρ L μ L − 1 ) 0.92 ( S c L ) 0.5 (mL mP−3). In this study the Liquid Schmidt number dependency of the gas–Liquid Mass Transfer coefficient points to the penetration theory describing the rate of Mass Transfer for gas–Liquid flow through solid foam packings.
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gas Liquid Mass Transfer enhancement in a surface aeration stirred slurry reactors
Canadian Journal of Chemical Engineering, 2008Co-Authors: K C Ruthiya, Bfm Ben Kuster, J Jaap C SchoutenAbstract:This paper postulates four possible mechanisms for the enhancement of gas-Liquid (G-L) Mass Transfer in slurry reactors: (1) hydrodynamic effect, (2) shuttling, (3) stabilization of bubbles, and (4) reaction enhancement. Mass Transfer and reactivity experiments using two different slurry systems and two different Pd-catalysed reactions, i.e., oxidation of glucose (aqueous phase) and hydrogenation of α-methyl styrene (organic phase), with both hydrophobic carbon and hydrophilic silica catalyst supports, were performed in a laboratory scale surface aeration reactor with a flat gas-Liquid interface. Physical and reaction enhancement have been distinguished successfully. The experimental results show that the level of catalyst support hydrophobicity has a strong influence on the rate of Mass Transfer.
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gas Liquid Mass Transfer and axial dispersion in solid foam packings
Chemical Engineering Science, 2007Co-Authors: C.p. Stemmet, Van Der John J Schaaf, Marco M Meeuwse, Bfm Ben Kuster, J Jaap C SchoutenAbstract:The Mass Transfer coefficient and other hydrodynamic parameters are presented for a gas and Liquid (air–water system) moving in a co-current upflow configuration through solid foam packings in the range of 10–40 pores per linear inch (ppi). Axial dispersion in the Liquid has been excluded by observing that the Liquid was in plug flow in the range of superficial Liquid and gas velocities studied (0.02
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Solid foam packings for multiphase reactors: Modelling of Liquid holdup and Mass Transfer
Chemical Engineering Research and Design, 2006Co-Authors: C.p. Stemmet, Bfm Ben Kuster, Van Der J John Schaaf, Jc Jaap SchoutenAbstract:In this paper, experimental and modeling results are presented of the Liquid holdup and gas–Liquid Mass Transfer characteristics of solid foam packings. Experiments were done in a semi-2D transparent bubble column with solid foam packings of aluminum in the range of 5–40 pores per inch (ppi). The relative permeability model described by Saez and Carbonell (1985) is used to describe the Liquid holdup data for solid foam packings of 5, 20 and 40 ppi. The investigated system variables are the superficial gas and Liquid velocities, using counter-current flow with maximum gas velocities and Liquid velocities of 0.8 m s −1 and 0.03 m s −1 , respectively. The relative permeability model is able to describe the Liquid holdup in the low Liquid holdup or trickle flow regime as well as in the high Liquid holdup regime, which resembles flow in a packed bubble column. Gas-to-Liquid Mass Transfer is modelled using the penetration theory. Mass Transfer coefficients up to 6 s −1 are predicted; these high values are largely due to the high specific surface area of the solid foam packings.
Van Der John J Schaaf - One of the best experts on this subject based on the ideXlab platform.
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gas Liquid Mass Transfer in a rotor stator spinning disc reactor
Chemical Engineering Science, 2010Co-Authors: Van Der John J Schaaf, Marco M Meeuwse, Bfm Ben Kuster, J Jaap C SchoutenAbstract:Abstract This paper describes a new multiphase reactor, the rotor–stator spinning disc reactor, which shows high rates of gas–Liquid Mass Transfer in comparison to conventional multiphase reactors. The volumetric gas–Liquid Mass Transfer coefficient k GL a GL in the rotor–stator spinning disc reactor increases with increasing rotational disc speed, due to the higher surface renewal rate caused by the increasing turbulence, and with increasing gas flow rate. Measured k GL a GL values are as high as 0.43 m L 3 m R - 3 s - 1 at 7.3 × 10 - 6 m 3 s - 1 gas flow and a rotational disc speed of 179 rad s - 1 , and are expected to increase even further at increasing rotational disc speed. This is twice as high as for conventional reactors as bubble columns, in spite of the low gas holdup of 0.021 m G 3 m R - 3 with only one gas inlet. The volumetric Mass Transfer per unit volume of gas, k GL a GL / ɛ G , of 20.5 m L 3 m G - 3 s - 1 is 40 times higher than 0.5 m L 3 m G - 3 s - 1 for a bubble column.
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influence of Liquid viscosity and surface tension on the gas Liquid Mass Transfer coefficient for solid foam packings in co current two phase flow
Chemical Engineering Research & Design, 2008Co-Authors: C.p. Stemmet, Van Der John J Schaaf, Bfm Ben Kuster, Frank F Bartelds, J Jaap C SchoutenAbstract:Abstract The gas–Liquid Mass Transfer coefficient and other hydrodynamic parameters such as Liquid holdup and frictional pressure drop are presented for gas and Liquid moving in co-current upflow and downflow through solid foam packings of 10 and of 40 pores per linear inch (ppi). The effect of increasing the Liquid viscosity on the Mass Transfer coefficient in co-current upflow is quantified and correlated to the frictional pressure drop, a measure of the frictional energy dissipation: k L a GL ɛ L ( S c L / S c water ) 0.69 = 2.05 × 1 0 − 4 P f 0.8 (mL3 mP−3 s−1). The gas–Liquid Mass Transfer coefficient in co-current downflow is correlated to the Liquid velocity and the Schmidt number using the correlation proposed by Sherwood and Holloway [Sherwood, T. and Holloway, F., 1940, Performance of packed towers—Liquid film data for several packings, Transactions of the American Institute of Chemical Engineers 36: 39–70]: k L a GL ɛ L D L − 1 = 3.7 ( u L ρ L μ L − 1 ) 1.16 ( S c L ) 0.5 (mL mP−3). The results for the gas–Liquid Mass Transfer coefficient in co-current upflow were correlated with a similar equation, where the influence of the gas velocity is included, similar to the correlations for packed beds of spherical particles proposed in Fukushima and Kusaka [Fukushima, S. and Kusaka, K., 1979, Gas–Liquid Mass Transfer and hydrodynamic flow region in packed columns with cocurrent upward flow, Journal of Chemical Engineering of Japan 12 (4): 296–301]: k L a GL ɛ L D L − 1 = 311 u G 0.44 ( u L ρ L μ L − 1 ) 0.92 ( S c L ) 0.5 (mL mP−3). In this study the Liquid Schmidt number dependency of the gas–Liquid Mass Transfer coefficient points to the penetration theory describing the rate of Mass Transfer for gas–Liquid flow through solid foam packings.
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gas Liquid Mass Transfer and axial dispersion in solid foam packings
Chemical Engineering Science, 2007Co-Authors: C.p. Stemmet, Van Der John J Schaaf, Marco M Meeuwse, Bfm Ben Kuster, J Jaap C SchoutenAbstract:The Mass Transfer coefficient and other hydrodynamic parameters are presented for a gas and Liquid (air–water system) moving in a co-current upflow configuration through solid foam packings in the range of 10–40 pores per linear inch (ppi). Axial dispersion in the Liquid has been excluded by observing that the Liquid was in plug flow in the range of superficial Liquid and gas velocities studied (0.02
Jochen Buchs - One of the best experts on this subject based on the ideXlab platform.
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advances in understanding and modeling the gas Liquid Mass Transfer in shake flasks
Biochemical Engineering Journal, 2004Co-Authors: Ulrike Maier, Mario Losen, Jochen BuchsAbstract:Abstract The gas–Liquid Mass Transfer in 250 ml shake flasks has previously been sucessfully modelled on basis of Higbie’s penetration theory. The current contribution presents advances in understanding and modelling the gas–Liquid Mass Transfer in shake flasks at waterlike Liquid viscosity in flask sizes between 50 and 1000 ml. An experimental investigation of the maximum gas–Liquid Mass Transfer capacity OTRmax using the sodium sulphite system was extended to relative filling volumes of 4–16%, shaking diameters of 1.25, 2.5, 5, 7, 10 cm and shaking frequencies of 50–500 rpm for the above flask sizes. Simultaneously, the previous model of the gas–Liquid Mass Transfer was extended to a “two sub-reactor model” to account for different mechanisms of Mass Transfer in the Liquid film on the flask wall and the bulk of the Liquid rotating within the flask. The shake flask is for the first time considered to be a two-reactor system consisting of a stirred tank reactor (bulk Liquid) and a film reactor (film on flask wall and base). The Mass Transfer into the film on the flask wall and base at “in-phase” operating conditions is described by Higbie’s penetration theory. Two different Mass Transfer theories were applied to successfully describe the Mass Transfer into the bulk Liquid: a model by Kawase and Moo-Young and a model by Gnielinski. The agreement between the new modelling approach, which requires absolutely no fitting parameters and the experimental is within ±30%. The applicability of the models to a biological system was shown using a Pichia pastoris culture. This is particularly notable since geometrically non-similar Liquid distributions in very different sizes of shaking flasks are covered. A comparable description of the gas–Liquid Mass Transfer in bubble aerated reactors like stirred tanks is absolutely out of reach. A spatially- and time-resolved consideration of the Mass Transfer in the Liquid film on the flask wall and base has shown that the validity of Higbie’s theory sensitively depends on the film thickness and contact time.
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characterization of gas Liquid Mass Transfer phenomena in microtiter plates
Biotechnology and Bioengineering, 2003Co-Authors: Robert Hermann, Mathias Lehmann, Jochen BuchsAbstract:Gas-Liquid Mass Transfer properties of shaken 96-well microtiter plates were characterized using a recently described method. The maximum oxygen Transfer capacity (OTR(max)), the specific Mass Transfer area (a), and the Mass Transfer coefficient (k(L)) in a single well were determined at different shaking intensities (different shaking frequencies and shaking diameters at constant filling volume) and different filling volumes by means of sulfite oxidation as a chemical model system. The shape (round and square cross-sections) and the size (up to 2 mL maximum filling volume) of a microtiter plate well were also considered as influencing parameters. To get an indication of the hydrodynamic behavior of the Liquid phase in a well, images were taken during shaking and the Liquid height derived as a characteristic parameter. The investigations revealed that the OTR(max) is predominantly dependent on the specific Mass Transfer area (a) for the considered conditions in round-shaped wells. The Mass Transfer coefficient (k(L)) in round-shaped wells remains at a nearly constant value of about 0.2 m/h for all shaking intensities, thus within the range reported in the literature for surface-aerated bioreactors. The OTR(max) in round-shaped wells is strongly influenced by the interfacial tension, determined by the surface tension of the medium used and the surface properties of the well material. Up to a specific shaking intensity the Liquid surface in the wells remains horizontal and no Liquid movement can be observed. This critical shaking intensity must be exceeded to overcome the surface tension and, thus, to increase the Liquid height and enlarge the specific Mass Transfer area. This behavior is solely specific to microtiter plates and has not yet been observed for larger shaking bioreactors such as shaking flasks. In square-shaped microtiter plate wells the corners act as baffles and cause a significant increase of OTR(max), a, and k(L). An OTR(max) of up to 0.15 mol/L/h can be reached in square-shaped wells.
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characterisation of the gas Liquid Mass Transfer in shaking bioreactors
Biochemical Engineering Journal, 2001Co-Authors: Ulrike Maier, Jochen BuchsAbstract:Abstract The maximum gas–Liquid Mass Transfer capacity of 250 ml shaking flasks on orbital shaking machines has been experimentally investigated using the sulphite oxidation method under variation of the shaking frequency, shaking diameter, filling volume and viscosity of the medium. The distribution of the Liquid within the flask has been modelled by the intersection between the rotational hyperboloid of the Liquid and the inner wall of the shaking flask. This model allows for the calculation of the specific exchange area ( a ), the Mass Transfer coefficient ( k L ) and the maximum oxygen Transfer capacity (OTR max ) for given operating conditions and requires no fitting parameters. The model agrees well with the experimental results. It was furthermore shown that the Liquid film on the flask wall contributes significantly to the specific Mass Transfer area ( a ) and to the oxygen Transfer rate (OTR).