The objective of this work was investigation of the hydrodynamics of the flow in Couette-Taylor flow (CTF) in the liquid-liquid system using the computational fluid dynamics software Fluent 6. Characteristic parameters for CTF such as the length of the Taylor vortex pair, axial translation velocity of the vortices and the Kolmogoroff micro-scale were estimated.
PL
Dokonano numerycznej symulacji hydrodynamiki dwufazowego przepływu Couette'a-Taylora w układzie ciecz-ciecz. W badaniach użyto pakietu obliczeniowego Fluent 6. Wyznaczono parametry charakterystyczne dla przepływu Couette.a-Taylora, takie jak: długość pary wirów Taylora, prędkość przepływu osiowego wirów oraz skalę Kołmogorowa w fazie ciągłej.
Przedstawiono koncepcje wykorzystania membranowego reaktora helikoidalnego do prowadzenia procesów gaz-ciecz-zawiesina. Rozważono jego modyfikację konstrukcyjną, tj. szczelinowy reaktor spiralny. Zbadano i przedyskutowano wpływ takich parametrów jak: prędkość obrotowa rotora, natężenia przepływu masowego mieszaniny dwufazowej oraz stosunek objętościowy obu faz na transport masy w układzie ciecz-gaz. Określono wpływ wzrostu lepkości cieczy na wartości objętościowych współczynników wnikania masy, uzyskując wysokie wartości tych współczynników, rzędu 10(-1)s(-1). Wskazano na możliwość zastosowania reaktora helikoidalnego w procesie mokrego utleniania zawiesin i osadów ściekowych.
EN
A concept of membrane CTF reactor and the possibility of using it for gas-liquid (slurry) processes have been presented. A modified CTF reactor with rotating shaft replaced by a static helicoidal ribbon guide was proposed. The effects of such parameters as the gas-liquid mixture mass flow rate, the ratio of volumetric flow rates of the phases: gas/liquid, a rotational speed of the internal cylinder on the mass transfer in a two-phase system was determined experimentally. The influence of the liquid viscosity increase on the values of the volumetric mass transfer coefficients has been investigated. Experiments indicate high values of the mass transfer coefficient, particularly in a high viscosity liquid. A possibility to use CTF reactor in the wet air oxidation process for slurry and sludge wastes treating.
Przedstawiono wyniki pomiarów mocy dyssypowanej ruchu obrotowego w dwufazowym przepływie Couette'a-Taylora dla układu ciecz-ciecz oraz struktury charakterystyczne dla takiego przepływu. Zaproponowano mapę reżimów przepływu. Obserwowane struktury przepływu sklasyfikowano w zależności od ułamka objętościowego fazy olejowej i zapotrzebowania na moc rotora.
EN
The measurements of the rotor power input were presented. Typical flow structures of liquid-liquid horizontal Couette-Taylor flow were described. The maps of the flow regime were presented. The observed regime was classified according to power input (connected with the rotor rotation) and volume fraction of silicone liquid.
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 [degrees]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.
Przedstawiono koncepcje wykorzystania membranowego reaktora helikoidalnego do prowadzenia procesów gaz-ciecz lub zawiesina, określono podstawowe właściwości hydrodynamiczne i kinetyczne reaktora. W badaniach wstępnych uzyskano wartości współczynników wnikania kLa, rzędu 10-(-1/s. Przedyskutowano wykorzystanie reaktora w procesie 'mokrego utleniania' szlamów i zawiesin.
EN
An idea of the use of a membrane helicoidal reactor in gas/liquid or suspensions processes as well as the determination of basic hydrodynamic and kinetic properties of the reactor are presented The convective mass transfer coeficient, kLa, of the order of 10(-1) 1/s has been obtained during primary investigations. The possible employment of such reactor in wet-air oxidation of slurries and suspensions is discussed.
Hydrodynamics of two-phase gas - liquid and liquid - liquid helicoidal flow has been presented. Experimental and numerical study of such flow was carried out.
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.
The immobilization of pollutants by irreversible sorption in agglomerates immersed directly into the porous layer has been considered. A general model for migration and sorption of soluble contaminants in a porous layer has been formulated and the method of its solution has been proposed. The calculations have been carried out to display the model effectiveness and flexibility. The influence of the size of agglomerates, the density and geometry of their distribution on the decontamination efficiency has been studied. Also the effect of mass transfer parameters on this efficiency has been investigated.
The study presents a method for emulsion preparation in the liquid - liquid contactor in conditions of Couette-Taylor flow (CTF). Stable 0/W emulsions with a quite narrow drop size distribution have been prepared. Emulsions tested can be used as an alternative diesel fuel of improved engine performance and emission characteristics.
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