The concept of a rotational rheometer with helical screw impeller

Kembłowski, Z.; Sęk, J.; Budzyński, P.

doi:10.1007/bf01372454

Cited by 35 publications

(7 citation statements)

References 9 publications

(7 reference statements)

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“…In order to overcome some of these limitations, Kemblowski et al 55 replaced the turbine with a helical screw impeller, which, because of the better mixing characteristics, allowed flow I -n n curve determination in a much wider shear rate range and also minimized the possibility of phase separation occurring. Preliminary studies of the on-line system using polyacrylamide and carboxymethylcellulose gave promising results, which clearly show the potential of such a system for continuous rheological monitoring of fermentation broths.…”

Section: On-line Instrumentsmentioning

confidence: 98%

Viscous Fermentation Products

McNeil

Harvey

1993

Critical Reviews in Biotechnology

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The viscous nature of fermentation broths has a marked effect on many parameters and process conditions within the bioreactor, often resulting in changes in microbial behavior and product formation. Although fermentation processes that involve significant changes in broth rheology have attracted much research interest, significant problems still remain. Particular difficulties remain in relation to processes where the broth develops pronounced non-Newtonian characteristics.This article reviews some of the models developed to describe these fermentation fluids and their limitations; the bioreactor types employed and their mode of operation; the problems encountered because of the nature of the fluids, for example, monitoring and control; and the gradients found in such systems. To illustrate the above, four specific processes are described in detail -the production of filamentous biomass (SCP) and three extracellular microbial polysaccharides, xanthan, pullulan, and scleroglucan.parative study on rheological properties of mycelial broth in filamentous and pelleted forms, Eur. J. Appl. Microhiol. Biotechnol., 18, 11 I , 1983. Byrne, G. S. and Warel, 0. P., Effect of nutrition on pellet formation by Rhizopus arrhizus, Biotechnol. Bioeng., 33, 912, 1989.

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Section: On-line Instrumentsmentioning

confidence: 98%

Viscous Fermentation Products

McNeil

Harvey

1993

Critical Reviews in Biotechnology

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“…First, the need for calibration with standard Newtonian and (or) non-Newtonian fluids and secondly, the assumption of a fixed value of impeller proportionality constant, k', where 9 = k'N. Therefore, the application of these methods in rheology has been questioned (Kemblowski et al 1988;Nienow and Elson 1988;Castell-Perez and Steffe 1992) and the need for new procedures to evaluate the rheological behavior of power-law fluids suggested. Barnes and Carnali (1 990) investigated the suitability of a vane type viscometer for shear-thinning and thixotropic materials using numerical methods.…”

Section: Introductionmentioning

confidence: 99%

Simple Determination of Power Law Flow Curves Using a Paddle Type Mixer Viscometer

Castell‐Perez

Steffe

Moreira

1991

Journal of Texture Studies

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A simple and accurate procedure to determine the flow properties of powerlaw fluids using a paddle type mixer viscometer is described. The approach considers the mixer as analogous to a concentric cylinder system and incorporates the inclusion of end effects in modeling. The procedure significantly reduces data collection because calibration with standard fluids is not necessary to estimate average shear stress and shear rate values.

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“…Furthermore, fermentation broths are three-phase systems, in which the presence of gas bubbles makes it very difficult to make a meaningful rheological measurement. While slit [25], vibrational [10], and rotational [26] devices have been proposed for this type of installation, none of these represents an ideal solution to the problem.…”

Section: Mulfiphase Systemsmentioning

confidence: 97%

Challenges in process rheometry

Dealy

1990

Rheol Acta

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Process rheometers are useful as process sensors for on-line quality control as well as for process control. Unlike passive sensors for equilibrium properties, such as temperature and pressure, a rheometer must subject the material of interest to a controlled deformation while monitoring the resulting stress. To accomplish this in a compact, robust device suitable for use in a manufacturing environment is not straightforward. Problems that arise in processing applications include the need for frequent sample renewal without interference from the measurement or the process itself and the fact that the process stream is usually under pressure. Considerable ingenuity has been applied to developing rheometers to meet these requirements.However, there remain many potential applications for which presently available units are not suitable. In particular, special problems arise when a very fast response is required, when the fluid being processed is non-Newtonian or has a very high viscosity, and when it is a multiphase system, as for example in the case of mineral slurries. In addition, in food processing and fermentation applications, all the exposed surfaces of the rheometer must be sterilizable. Possible solutions to these problems are described.

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The concept of a rotational rheometer with helical screw impeller

Cited by 35 publications

References 9 publications

Viscous Fermentation Products

Viscous Fermentation Products

Simple Determination of Power Law Flow Curves Using a Paddle Type Mixer Viscometer

Challenges in process rheometry

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