Prediction of mass transfer coefficients in non‐Newtonian fermentation media using first‐principles methods

Radl, Stefan; Khinast, Johannes G.

doi:10.1002/bit.21323

Cited by 16 publications

(9 citation statements)

References 28 publications

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“…Ohta et al [9,10] explored both experimentally and numerically the motion of a Newtonian, spherical and deformable drop rising in shearthinning fluids using the VOF method. Radl et al [11,12] Newtonian fluids and associated mass transfer using first principle methods. As the stability of numerical schemes depends strongly on the ratio between liquid and gaseous phase densities and viscosities, the above investigations [7,8,11,12] represent the bubble using a Newtonian drop of low density.…”

Section: Introductionmentioning

confidence: 99%

“…Radl et al [11,12] Newtonian fluids and associated mass transfer using first principle methods. As the stability of numerical schemes depends strongly on the ratio between liquid and gaseous phase densities and viscosities, the above investigations [7,8,11,12] represent the bubble using a Newtonian drop of low density. That is, the density and viscosity ratios of liquid over gas phase were up only to 10, which was much lower than that in real cases ( l / g ∼ 10 3 and Á l /Á g ∼ 10 4 ).…”

Section: Introductionmentioning

confidence: 99%

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Numerical simulation of a bubble rising in shear-thinning fluids

Zhang

Yang

Mao

2010

Journal of Non-Newtonian Fluid Mechanics

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a b s t r a c tThe motion of a single bubble rising freely in quiescent non-Newtonian viscous fluids was investigated experimentally and computationally. The non-Newtonian effects in the flow of viscous inelastic fluids are modeled by the Carreau rheological model. An improved level set approach for computing the incompressible two-phase flow with deformable free interface is used. The control volume formulation with the SIMPLEC algorithm incorporated is used to solve the governing equations on a staggered Eulerian grid. The simulation results demonstrate that the algorithm is robust for shear-thinning liquids with large density ( 1 / g up to 103 ) and high viscosity (Á 1 /Á g up to 10 4 ). The comparison of the experimental measurements of terminal bubble shape and velocity with the computational results is satisfactory. It is shown that the local change in viscosity around a bubble greatly depends on the bubble shape and the zero-shear viscosity of non-Newtonian shear-thinning liquids. The shear-rate distribution and velocity fields are used to elucidate the formation of a region of large viscosity at the rear of a bubble as a result of the rather stagnant flow behind the bubble. The numerical results provide the basis for further investigations, such as the numerical simulation of viscoelastic fluids.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Numerical simulation of a bubble rising in shear-thinning fluids

Zhang

Yang

Mao

2010

Journal of Non-Newtonian Fluid Mechanics

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“…Another approach is the front‐tracking (FT) method,29, 51 where a separate grid is used to track the front, whereas the conservation equations are solved on a fixed uniform grid. With such methods, very high accuracy, even for complex flows, can be achieved 52…”

Section: Introductionmentioning

confidence: 99%

Flow and mass transfer of fully resolved bubbles in non‐Newtonian fluids

2007

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In this work, high-resolution 2-D numerical simulations were performed on the motion of deformable bubbles in non-Newtonian fluids and the associated mass transfer. For that purpose, we have implemented a semi-Lagrangian advection scheme and improved the fluid dynamic calculation by the usage of implicit algorithms. Non-Newtonian fluids are described by generalized Newtonian as well as viscoelastic model fluids. As shear-thinning model we use a Power-Law and a Carreau-Yasuda model, the viscoelastic fluid simulations are based on an Upper-Convected Maxwell model combined with a recently introduced model for the evolution of the effective shear rate. The mathematical challenges arising from the hyperbolic nature of the resulting set of equations are addressed by inclusion of artificial diffusion in the stress equation. In our work, it was found that shear thinning effects have impact on collision rates, and therefore, may influence coalescence of bubbles in non-Newtonian liquids. Furthermore, for the first time, concentration fields of dissolved gas in viscoelastic fluids are presented. The study shows that the fluid elasticity plays a major role for bubble rise velocity, and therefore, mass transfer. As the wake dynamics differ significantly from that in Newtonian liquids, abnormal mixing characteristics can be expected in the bubbly flow of viscoelastic fluids. 2007 American Institute of Chemical Engineers AIChE J, 53: [1861][1862][1863][1864][1865][1866][1867][1868][1869][1870][1871][1872][1873][1874][1875][1876][1877][1878] 2007 Keywords: numerical simulation, bubbles, non-Newtonian liquids, mass transfer IntroductionBecause of persistent uncertainties in the underlying models and system properties, the scale-up of bioreactors remains a challenging problem. For example, the rheology of media in bioreactors is non-Newtonian in most cases. [1][2][3][4][5][6][7][8] However, details of the non-Newtonian fluid characteristics, such as viscoelasticity or the tendency for shear thinning, are frequently unknown or neglected. Furthermore, in contrast to Newtonian media, there is a lack of general correlations for mass and heat transfer rates, which are needed for the prediction of oxygen supply and heat removal. Similar observations can be made for the properties needed to precisely predict transport of metabolites, nutrients, or CO 2 . So far, most studies are based on experimental investigations, which are usually interpreted with simple theoretical models. 3,4,[8][9][10][11] principles methods to predict mass-transfer coefficients, transport rates, and other parameters in non-Newtonian fluids have not been reported so far. Local mass transfer is not the only micro-effect of central importance in the design of bioreactors. Knowledge of the localized forces, such as shear and normal stresses in the cell's microenvironment, is also a key for determining whether a bioreactor is suitable to handle sensitive biosystems.12 Subcritical shear stresses found in the hydrodynamic environment of large-scale reactors may redu...

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“…Mass transfer and transport coefficients, knowledge of shear rates, and the resulting stress distribution in aerated and nonaerated Newtonian and non-Newtonian liquids are important to determine whether a bioreactor is suitable to handle shear-sensitive biosystems (Al-Masry, 1999;Radl and Khinast, 2007). Damage to fragile microorganisms, biofilms, and immobilized biocatalysts due to high shear rates have been reported (Duddridge, Kent, and Laws, 1982;Lau and Liu, 1993;Gjaltema et al, 1995Gjaltema et al, , 1997Martins dos Santos et al, 1997).…”

Section: Cell Damagementioning

confidence: 98%

Critical analysis of engineering aspects of shaken flask bioreactors

Suresh

Srivastava

Mishra

2009

Critical Reviews in Biotechnology

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Shaking bioreactors are the most frequently used reaction vessels in biotechnology. Since their inception, shaking bioreactors have been playing a significant role in medicine, agriculture, food, environmental, and industrial research. In spite of their huge practical importance, very little is known about the characteristic properties of shaken cultures from an engineering point of view. In this paper, a critical analysis is presented of the mixing characteristics, aeration, mass and heat transfer, power consumption, and suitability for on-line monitoring and control of various environmental and other operating parameters in aerated and anaerobic/anoxic conditions. Aspects of cell damage due to shear stress generated in shaken flask and loss of sterility due to contamination are also discussed.

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Prediction of mass transfer coefficients in non‐Newtonian fermentation media using first‐principles methods

Cited by 16 publications

References 28 publications

Numerical simulation of a bubble rising in shear-thinning fluids

Numerical simulation of a bubble rising in shear-thinning fluids

Flow and mass transfer of fully resolved bubbles in non‐Newtonian fluids

Critical analysis of engineering aspects of shaken flask bioreactors

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