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Movement Periodicity of Wobbling Ellipsoidal Bubbles
Machačová, K. ; Raška, P. ; Wichterle, K. ; Večeř, Marek ; Růžička, Marek
Experiments with bubbles observed in countercurrent flow allow us to study movement of bubbles for long time period and diagnose their speciality. The oscillations of bubble velocity and shape deformation are statistically treated in this work for ellipsoidal bubbles. Prevailing behavior of these bubbles is movement from side to side (zig-zag) with small inclination to helical one. Simple model describing the hydrodynamic causation of horizontal oscillations and their magnitude was suggested. Typical values for bubbles with equivalent diameter from 4 to 10 mm are: rising velocity 200-300 mm/s, maximum lateral velocity 150 mm/s and oscillation frequency 6 Hz. Good agreement between our results and recent publications is enunciate.
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Enzyme Catalysed Hydrolysis in a Continuous-Flow Reactor
Bernášek, Prokop ; Sovová, Helena
Hydrolysis of black currant (Ribes nigrum) seed oil was carried out in supercritical carbon dioxide medium; the substrates dissolved in CO2 passed a reactor containing immobilised enzyme Lipozyme. Conversion of the fatty acid esters to free fatty acids was examined in dependence on the amount of enzyme in the reactor and on the solution flow rate. A rapid colorimetric method was developed for determination of the sum of free fatty acids in the reaction mixture. Other analytical procedures were applied to perform a more complex investigation of fatty acid composition: partial esters of fatty acids were determined using HPLC and the free alfa- and gamma-linolenic acids were distinguished using LC-NMR.
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Transport Parameters and Textural Properties of Porous Solids
Soukup, Karel ; Šolcová, Olga ; Schneider, Petr
Based on a study of a set of porous materials with wide range of mean pore radii (from 50 to 3000 nm) and mono- or bidisperse pore structure, transport characteristics and textural properties are compared. Structure characteristics relevant to transport processes were evaluated from multicomponent gas diffusion and gas permeation measurements. For data analysis the Mean Transport Pore Model (MTPM) based on Maxwell - Stefan diffusion equation and Weber permeation law was used. Two standard methods - physical adsorption of nitrogen and mercury porosimetry (ASAP2010M and AutoPore 9200, Micromeritics, USA) were used for determination of textural properties. Results from liquid expulsion permporometry that correspond to situation in industrial processes were also taken into account.
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Efektivní difuzivity a transportní charakteristiky monolitických automobilových konvertorů s nanesenou vrstvou katalyzátoru
Starý, T. ; Šolcová, Olga ; Schneider, Petr ; Marek, M. ; Schejbal, M.
The effective diffusivity in the pores of catalytic monolith was studied in single pellet-string columns by chromatographic technique. The column was packed with small monolith particles. Dispersion due to extra column effects was eliminated via convolution of responses for two column lenghts. The measurements were done for both cordierite support with alumina based washcoat. The effective diffusion coefficients for two tracer-carrier pairs were evaluated by fitting column response (chromatographic) peaks in time domain. Mean transport parameters were evaluated for both types of porous particles. Obtained mean transport pore radii are in reasonable agreement with pore size distribution from mercury porosimetry.
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