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Shape of So-Called Ellipsoidal Bubbles Rising in a Liquid
Wichterle, K. ; Smutná, K. ; Večeř, Marek
Small bubbles have a spherical shape. Big bubbles are of an unstable shape. The shape of a big bubble resembles that of pulsating hemisphere with a flat or concave base. Relatively stable medium-sized bubbles are interesting in view of technical applications. The medium-sized bubbles have approximately a shape of an oblate ellipsoid. Shape of smaller bubbles in low viscosity liquids is determined by gravitational force and surface tension force. Eötvös number comprises of the gravitational and surface tension forces. Ellipsoidal shape is expected for 0,2 < Eo < 30. This corresponds to bubbles in water with bubble size 1 - 2000 mm3. Longstanding records of bubble motion made possible to evaluate bubble shape and shape oscillations. Volume of recorded bubbles was 10 to 800 mm3, water and glycerol solutions were used as liquids. A ratio of horizontal and vertical bubble size, given in literature, is correct in principle.
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Hydrogenation of Tar Precursors in Pyrolysis Gasoline.
Sazanov, Z. ; Tukač, V. ; Chyba, V. ; Handlová, M. ; Hanika, Jiří ; Lederer, J. ; Kolena, J.
Experimental series were focused on catalytic hydrogenation of unsaturated components in pyrolysis gasoline: styrene, consecutive hydrogenation of dicyclopentadiene (DCPD) via dihydrodicyclopentadiene (DHDCPD) to tetrahydrodicyclopentadiene (THDCPD), indene, allylbenzene, 4-methylstyrene, 3-methylstyrene and 4-methylstyrene. Hydrogenation was investigated at temperature 30, 40 a 60°C and under hydrogen pressure 2 a 5 bar using Noblyst Degussa 1505 (0,1 hm. % Pd/ ? - Al2O3) catalyst.
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Unsaturated Hydrocarbons Hydrogenation in Trickle Bed Reactor during Periodic Feed Rate Modulation.
Chyba, V. ; Tukač, V. ; Handlová, M. ; Hanika, Jiří ; Sazanov, Z. ; Lederer, J. ; Kolena, J. ; Jiřičný, Vladimír ; Stavárek, Petr ; Staněk, Vladimír ; Kubička, D. ; Kubičková, I.
Effects of following feed rate modulation parameters on styrene and dicyclopentadiene hydrogenation in toluene and pyrolysis gasoline were investigated in pilot plant experiments: period length, its split, liquid feed rate and liquid rich to liquid poor period parts ratio. The catalyst deactivation was investigated too. Pilot plant results indicated 10% higher trickle bed reactor throughput by application of periodic feed rate modulation in comparison to steady state operation regime.
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CFD Model of Pyrolysis Gasoline Hydrogenation in Trickle Bed Reactor.
Tukač, V. ; Handlová, M. ; Hanika, Jiří ; Chyba, V. ; Sazanov, Z. ; Lederer, J. ; Kolena, J. ; Jiřičný, Vladimír ; Stavárek, Petr ; Staněk, Vladimír
Paper proposes hierarchic structure of mathematical models of pyrolysis gasoline hydrogenation in trickle bed reactor using egg-shell type catalyst. Model dimensions cover an interval from 3 mm of catalyst pellet diameter over a string of several catalyst pellets trickled by reaction mixture to finaly pilot plant trickle bed reactor of diameter 100 mm. Hydrodynamics, transport phenomena and chemical reaction kinetics were desribed by differential balances which were solved by a finite difference method using COMSOL Multiphysics software.
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Analysis of Gas Transport through Macroporous Media.
Čapek, P. ; Hejtmánek, Vladimír
The aim of this study was to evaluate diffusional and forced flow in the cylindrical capillary under defined boundary conditions and to determine the effective diffusivities of gases (hydrogen, nitrogen, helium, and argon) in selected macroporous media. The knowledge of these diffusional and forced flow densities helps us to formulate many demands on the experimental apparatus and to estimate the error of the effective diffusivity. The relation between molar flux and the molar concentration gradient was described by the model of the mean transport pore. The experimental values of the effective diffusivities have agreed with the ones calculated for porous media replicas very well.
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Mathematical Optimisation of Geometry of the Microstructured Bipolar Electrolyser
Kodým, R. ; Bystroň, T. ; Křišťál, Jiří ; Jiřičný, Vladimír ; Bouzek, K.
In this work a 3-dimmensional mathematical model of the secondary current density distribution has been proposed and implemented. A parametric study of the influence of selected geometrical parameters, electrolyte conductivity and current load on the parasitic current value was performed. The Laplace equation describing the Galvani potential distribution was solved by Finite Element Method in COMSOL Multiphysics^TM environment. The mathematical model results have shown that the value of parasitic current is mainly affected by the electrolyte conductivity and interelectrode distance (i.e. active cross-section of the electrolyte distributors). Using the geometry optimization the parasitic currents have been minimized to an acceptable value, i.e. below the 5% of the total current load.
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