Shear Rates on Turbine Impeller Blades

Wichterle, Kamil; Kadlec, Miroslav; Žák, Leo; Mitschka, P.

doi:10.1080/00986448408940200

Cited by 45 publications

(22 citation statements)

References 13 publications

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“…It is therefore important to determine how velocity Similarly to the velocity distribution, the average and 90 th percentile values of the macro-shear rate distributions increase linearly with the ratio N/Njs, equal to the impeller rotational speed normalised by the just-suspensed speed, N js ( Figure 6). This linear evolution has already been observed by Oldshue (1983) and Wichterle et al (1984). The ratio between 90 th percentile and the average value of macro-shear rate distribution equals approximately 2.5.…”

Section: Evolution Of Velocity Fields and Mechanical Constraints As Asupporting

confidence: 80%

Axial impeller selection for anchorage dependent animal cell culture in stirred bioreactors: Methodology based on the impeller comparison at just-suspended speed of rotation

Collignon

Delafosse

Crine

et al. 2010

Chemical Engineering Science

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Animal cells, which are nowadays essential for the industrial production of proteinic compounds, are commonly cultivated inside stirred tank bioreactors. In case of anchorage dependent cells, they are usually fixed on microcarriers. The choice of agitation conditions (impeller type, rotational speed…) in this type of process is not an easy task as it has to fulfil three potentially conflicting goals: (1) maintaining microcarriers in complete suspension, (2) homogenizing the culture medium, and (3) limiting mechanical constraints generated by the hydrodynamics on the cells. The aim of this study is to present an original methodology to select the most appropriate axial impeller for this specific application. Seven propellers are preselected on basis of their characteristics available in the literature. Instead of comparing impellers at a given rotational speed or a given power input, they are compared at their respective minimum impeller rotational speed that leads to a complete microcarrier suspension, i.e. at their respective just-suspended speed N js . They are then compared at higher rotational speeds N, expressed as multiples of N js . The impeller classification is based on the intensity of mechanical constraints they produced, evaluated from: (1) the macro-shear rate quantified by the spatial derivative of time average velocity fields measured by P.I.V, (2) the micro-shear rate characterized by the ratio between the microcarrier diameter to the average Kolmogorov scale computed from power input measurements, and (3) Corresponding author: Tel: +32 4 366 47 22 -Fax:+32 4 366 28 18 E-mail address : mlcollignon@ulg.ac.be respectively). Moreover, the mechanical constraints they produce increase more slowly with the N/N js ratio than the mechanical constraints produced by other impellers. These propellers are thus even more advantageous if rotational speeds higher than the just-suspended speed have to be used

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Section: Evolution Of Velocity Fields and Mechanical Constraints As Asupporting

confidence: 80%

Axial impeller selection for anchorage dependent animal cell culture in stirred bioreactors: Methodology based on the impeller comparison at just-suspended speed of rotation

Collignon

Delafosse

Crine

et al. 2010

Chemical Engineering Science

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“…The MMW of the alginate produced by the bacteria increased as OTRmax (at the beginning of the culture) decreased. For the cultures carried out at 340 rpm, the OTR max was 8.0 mmolO2h -1 L -1 , but when the alginate concentration was increased the OTR profiles likely followed the Witchterle et al (1984) correlation or the proposition made by Vogel and Kroner (1999). In this case, the maximum MMW of the alginate was obtained at 1.0 mmolO2h -1 L -1 and the MMW obtained was 1.08 x 10 6 g/gmol.…”

Section: Vol Um Etri C Oxygen Tr An Sfer Co Effi Ci Ent (Kla) and O Xmentioning

confidence: 89%

“…Figure 2c shows the hipothetical k La evolution through the fermentation at several alginate concentra tions. For example, at 5.0 g/L of alginate, the major values were obtained with Witchterle et al (1984) and Vogel and Kroner (1999) correlations (4.4 y 4.0 h -1 , respectively), whereas the correlation proposed by Metzner and Otto (1957) was only about 2.6 h -1 . The same profiles of k La can be observed in the cultures performed at 140, 180, and 200 rpm.…”

Section: Vol Um Etri C Oxygen Tr An Sfer Co Effi Ci Ent (Kla) and O Xmentioning

confidence: 93%

“…W hen the alginate begins to synthesize and accumulate in the broth culture, the OTR diminished drastically and their value depends on the shear rate correlation used in the virtual sens or. For example, at 140 rpm the OTR value diminished from 3.1 to 0.66 mmolO2 L -1 h -1 at alginate concentrations for 3.0 g/L and these values were achieved with Witchterle et al (1984) correlation; but these values are less when were used the other shear rate correlations.…”

Section: Vol Um Etri C Oxygen Tr An Sfer Co Effi Ci Ent (Kla) and O Xmentioning

confidence: 94%

“…This parameter has been used recently by Campesi et al (2009) to determine the average shear rate caused by Rushton impellers during S. clavuligerus cultivations. At 140 rpm, the total oxygen supplied to the culture through 80 hours of cultivations varies according to the shear rate correlation used, for example, wi th Calderbank and Moo-Young proposal (Calderbank and MooYoung, 1959), 1.3 gO2 are provided to the cultures, while the correlation proposed by Witchterle et al (1984) are supplied 3.63 gO 2. Figure 3a shows all the trial simulations of the virtual sensor and indicate that the Witchterle et al (1984) and Vogel and Kroner (1999) correlations could model better the growth of the bacteria.…”

Section: Vol Um Etri C Oxygen Tr An Sfer Co Effi Ci Ent (Kla) and O Xmentioning

confidence: 99%

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