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Perfluorodecalin (PFD) is extensively applied as liquid carrier of gaseous metabolites in systems for in vitro cultures of various types of cells. The influence of Pluronic F-68 on modification of the surface properties of few liquid/liquid system containing PFD was discussed. Static surface and interfacial tensions (σ) of water/PFD, culture medium/PFD, as well as air/water (referentially) two-phases systems with the aqueous phase contained nonionic 3-block copolymer Pluronic F-68, were measured by the du Nouy ring method at 25 °C and 37 °C. Values of critical micelle concentration (CMC) for Pluronic F-68 dissolved in water/PFD and air/water systems were similar at constant temperature. Smaller value of maximum surface excess (Γ∞) and higher value of minimum surface area per adsorbed molecule (Amin) were obtained for water/PFD, than for water/air system. Increase of temperature from 25 °C to 37 °C resulted in significant decrease of CMC, decrease of Γ∞ and increase of Amin. Calculated value of the standard Gibbs free energy of micellization was negative and became more negative for higher temperature, what indicated that micelles were formed spontaneously and the tendency for micelle formation increased with temperature increase. The Frumkin model fits well the experimentally obtained values of σ, what has been proved by the coefficient of determination equaled to 0.994–0.996.

In this paper, thermal processing of starch slurry in a Couette-Taylor flow (CTF) apparatus was investigated. Gelatinized starch dispersion, after treatment in the CTF apparatus, was characterized using such parameters like starch granule diameters (or average diameter), starch granule swelling degree (quantifying the amount of water absorbed by starch granules) and concentration of dissolved starch. These parameters were affected mostly by the process temperature, although the impact of the axial flow or rotor rotation on them was also observed. Moreover, the analysis of results showed a relatively good correlation between these parameters, as well as, between those parameter and apparent viscosity of gelatinized starch dispersion. Meanwhile, the increase in the value of the apparent viscosity and in shear-tinning behaviour of dispersion was associated with the progress of starch processing in the CTF apparatus. Finally, the CTF apparatuses of different geometries were compared using numerical simulation of the process. The results of the simulation indicated that the apparatus scaling-up without increasing the width of the gap between cylinders results in higher mechanical energy consumption per unit of processed starch slurry.

In food industries, enzymatic starch hydrolysis is an important process that consists of two steps: gelatinization and saccharification. One of the major difficulties in designing the starch hydrolysis process is the sharp change in its rheological properties. In this study, Taylor–Couette flow reactor was applied to continuous starch hydrolysis process. The concentration of reducing sugar produced via enzymatic hydrolysis was evaluated by varying operational variables: rotational speed of the inner cylinder, axial velocity (reaction time), amount of enzyme, and initial starch content in the slurry. When Taylor vortices were formed in the annular space, efficient hydrolysis occurred because Taylor vortices improved the mixing of gelatinized starch with enzyme. Furthermore, a modified inner cylinder was proposed, and its mixing performance was numerically investigated. The modified inner cylinder showed higher potential for enhanced mixing of gelatinized starch and the enzyme than the conventional cylinder.

The definition of Reynolds number (Re) in a Taylor-Couette flow for a shear-thinning fluid is discussed in this paper. Since the shear-thinning property causes spatial distribution of fluid viscosity in a Taylor-Couette flow reactor (TCFR), a method to determine Re by using a numerical simulation is suggested. The effective viscosity (η eff) in Re was the average viscosity using a weight of dissipation function $$ {\eta}_{\mathrm{eff}}={\displaystyle \sum_{i=1}^N{\overset{\cdot }{\gamma}}_i^2{\eta}_i\Delta {V}_i}/{\displaystyle \sum_{i=1}^N{\overset{\cdot }{\gamma}}_i^2\Delta {V}_i}, $$ where N is the total mesh number, η i (Pa·s) is the local viscosity, $$ {\overset{\cdot }{\gamma}}_i $$ (1/s) is the local shear-rate, and ΔV i (m3) is the local volume for each cell. The critical Reynolds number, Re cr, at which Taylor vortices start to appear, was almost the same value with the Re cr obtained by a linear stability analysis for Newtonian fluids. Consequently, Re based on η eff could be applicable to predict the occurrence of Taylor vortices for a shear-thinning fluid. In order to understand the relation between the rotational speed of the inner cylinder and the effective shear rate that resulted in η eff, a correlation equation was constructed. Furthermore, the critical condition at which Taylor vortices appear was successfully predicted without further numerical simulation.

In this study, a Taylor-Couette flow reactor (TCFR) was applied to starch hydrolysis accompanied with an intricate viscosity change during reaction for the purpose of process intensification. In industries, several reactors are used in starch hydrolysis, namely gelatinization, liquefaction, and saccharification. It was possible to conduct a continuous starch hydrolysis with one TCFR. In addition, a sufficient reducing sugar yield was obtained in the Taylor vortex flow regime. However, the yield decreased at a higher effective Reynolds number (Reeff) due to axial dispersion through a bypass flow generated by the wavy motion of Taylor cells. In order to immobilize Taylor vortex flow at this condition, a ribbed inner cylinder was employed which suppressed axial dispersion at the higher Reeff. As a result, a higher reducing sugar yield was successfully obtained than that by using a standard cylinder, demonstrating that the optimization of TCFR geometry has the potential for process intensification.

In this paper, the flow patterns observed in horizontal Couette-Taylor flow (CTF) were correlated using dimensionless numbers. The analysis of the results showed that the structure of the flow was an outcome of interaction between fluid inertia related to axial and rotational flows and gravitation. Therefore, the flow structures were correlated using axial and angular Reynolds numbers, and Archimedes number for the given value of gas-to-liquid flow ratio. Finally, the correlation for the prediction of the transition to the flow regime observed at high rotational speeds was proposed. The comparison with experiments carried out in the vertical CTF from the literature showed that this correlation can also be useful in the case of vertical flow.

Starch gelatinization and enzymatic hydrolysis was carried out in a continuous Couette–Taylor flow reactor with a water jacket. The degree of gelatinization and the concentration of reducing sugars produced via enzymatic saccharification were evaluated by varying operational variables: rotation speed of an inner cylinder, initial concentration of starch and reaction temperature. At the initial concentration of the starch suspension, 50 kg m−3, starch saccharification proceeded sufficiently even at low rotation speed of the inner cylinder and saccharification temperature. At the higher initial concentration, 100 and 150 kg m−3, a higher rotation speed of the inner cylinder and temperature of the saccharification section were required to obtain sufficient starch saccharification. Even in the case of C0 = 100 and 150 kg m−3, the more reducing sugar was obtained by choosing an adequate rotation speed of the inner cylinder and a reaction temperature.

Couette–Taylor flow (CTF), which is characterized by the presence of Taylor vortices, ensures effective mixing, fast heat transfer and improved rheological properties of starch slurry. Therefore, this type of flow can be expected to provide favorable conditions for starch processing. In order to check how to intensify the process, starch gelatinization has been studied experimentally and using computer simulation in two CTF apparatuses of different volumes. The results show that, when the volume of apparatus was small, high value of degree of starch gelatinization could be achieved at relatively low temperature or at relatively low rotor rotation frequency. The increase in the apparatus volume ensures higher rate of gelatinized starch production and the reduction in dissipation of mechanical energy connected with rotor rotation, however, it also amplifies the detrimental inlet and gravitation effects. To overcome both of these negative effects, the increase in the rotor frequency is required. Practical Application Starch gelatinization is a process frequently encountered in food industry, e.g., food sterilization or starch hydrolysis. Therefore, a new way of starch processing could be interesting in the context of growing consumer interest in natural food. It is expected that CTF apparatus could enable to process much more concentrated starch slurry than a jet cooker or coil heater typically used in industrial setting. Starch granules should also be less damaged during treatment in CTF apparatus than in an extruder. The results presented in this paper are relevant for process intensification and scale-up of starch gelatinization in CTF apparatus and will be extended to simultaneous starch gelatinization with enzymatic hydrolysis in the future work.

Starch gelatinisation in Couette-Taylor flow apparatus In this paper starch gelatinisation in Couette-Taylor flow (CTF) apparatus (equipped with a water heat jacket) has been investigated. CTF (characterised by the presence of Taylor vortices) provides good environment for gelatinisation, e.g. effective mixing, fast heat transfer, positive influence on starch rheological properties. During experiments starch gelatinisation degree and starch swelling has been studied. It was accompanied by temperature measurements performed along the apparatus. Additionally, starch gelatinisation was investigated by computer simulation. A complete starch gelatinisation was obtained for the shortest investigated residence time in the apparatus when the temperature in the heat jacket was above 85 °C. Nevertheless, it seems that it is still possible to reduce a residence time value, as well as, the value of Thj, but it may require some acceleration of rotor rotation. The swelling degree of gelatinised starch increased with growing values of residence time, rotor rotation and process temperature. Heat transferred could be affected by the structure of the Taylor vortex flow. No significant destruction of starch granules was observed during the treatment in Couette-Taylor flow apparatus. A quite satisfactory agreement between computer simulation and experiments results was achieved.

This study presents a method of preparing simple and multiple emulsions formed in a liquid-liquid contactor with Couette-Taylor flow (CTF). A Couette-Taylor flow contactor represents a mini-channel device, and due to its small dimension can be connected to a diesel engine for just-prepared emulsion injection. Stable simple W/O and multiple O/W/O emulsions have been prepared, both with quite narrow drop size distribution. The mean drop size of the inner phase of multiple emulsions is in range of 2–10 μm depending on the operating conditions. Simple and multiple emulsions will be considered as an alternative diesel fuel for improving engine performance and emissions characteristics.

Interfacial area was measured in a helicoidal reactor for the two-phase gas–liquid flow. Measurements were accomplished using the method of oxygen chemical absorption in alkaline solutions of Na2S2O4. The process parameters were varied within the following ranges: rotational speed of impeller from 0 to 2900 rpm; liquid mass flux from 2.7 to 100 kg/(m2 s); volumetric flow ratio of gas and liquid from 0.125 to 1; ratio of impeller diameter to the outer reactor diameter from 0.54 to 0.92. Large values of the interfacial area were found. It was established that they depend mainly on the rotational speed of the rotor and to much less extent on the axial flow velocity. A correlation between changes in the interfacial area and changes in the flow structure within the reactor was also observed.

The results of the measurements of mass transfer coe$cients for the physical (CO /water) and chemical absorption (oxidation of benzaldehye) have been presented. The collected experimental data have been correlated with the energy dissipated in the system. High values of the mass transfer coe$cients, k a, of the order of 10 s have been obtained. 2001 Elsevier Science Ltd. All rights reserved.

A concept of membrane CTF (Couette-Taylor flow) reactor applicable to gas-liquid processes has been presented. Its fundamental hydrodynamic and kinetic properties have been discussed. In the experiments high values of the mass transfer coefficients, k L a, of the order of 0.1 s -1 have been obtained and a relatively weak influence of the liquid viscosity on the values of the mass transfer coefficients has been observed. To eliminate moving elements of the reactor, a replacement of the rotor by a static helical ribbon guide which forces the helicoidal flow of the fluid has been proposed for the same operating conditions.