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Termodynamické možnosti a omezení pro výrobu čistého vodíku pomocí železa s využitím cyklického chemického procesu za nižších teplot
Svoboda, Karel ; Slowinski, G. ; Rogut, J. ; Siewiorek, A.
Iron offers possibility of transformation of a reducing gas ( CO, syngas, methane etc.) into hydrogen by a cyclic process based on iron oxide reduction and release of hydrogen in the next step by steam oxidation. Thermodynamics and chemical equilibrium for reduction of magnetite by hydrogen, carbon monoxide, model syngas and methane and for oxidation of iron by steam has been studied in a temperature range 400 – 850 K. Attention was concentrated also on possible formation of undesired soot, iron carbide and iron carbonate as precursors for CO and CO2 formation in the steam oxidation step. Oxidation of iron by steam is thermodynamically favoured at temperatures 400 – 800 K enabling high hydrogen yields. Iron oxide (magnetite) reduction is the more difficult step, requiring rather higher temperature and higher CO, H2 or methane concentrations in gaseous mixtures.
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Numerické modelování impaktního proudění tekutiny na stěnu a experimentální ověření výsledků pomocí teplotní anemomerie
Cvetinović, D. ; Tihon, Jaroslav ; Vejražka, Jiří ; Drahoš, Jiří
The configuration of a submerged, circular, unconfined impinging air jet, which issues from a bell-shaped converging nozzle, is characterized numerically and experimentally. A commercial CFD package is repeatedly employed to simulate three different configurations to validate the different turbulence models, namely k–? Re-Normalized Group (RNG), k–? Shear Stress Transport (SST) and the Reynolds Stress Model (RSM). A hot-wire anemometry technique is applied to investigate extensively the flow field of the impinging jet. The comparison of results suggests that the k–? SST turbulence model is the most reliable for the flow configurations under investigation.
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Lokální charakterizace tokového pole v bublané koloně generované pomocí CFD
Fialová, Marie ; Staykov, P. ; Vlaev, S.D.
This study is aimed at 3-D simulation of bubble column using commercial CFD code Fluent and generating experimental local gas hold-up distribution profiles at different bed height positions, comparing these profiles with model solutions and demonstrating the flow field variation (vector plots for air and liquid movement) obtained by CFD modeling. Overall gas volume fraction values predicted by the CFD simulation were matched to measured values and showed comparable. CFD modeling was found to describe satisfactorily bubble bed formation in the bubble column operating with water and low viscosity solution.
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