Browsing by Author "Moutafchieva D."

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    Gas hold-up prediction in gas - liquid stirred tank reactor using CFD simulation
    (2014-01-01) Stoykova R.; Moutafchieva D.; Popova D.; Iliev V.
    This paper presents results from CFD simulation of gas-liquid mixing in an aerated stirred tank reactor. The ANSYS CFX simulation program method has been used to predict the distribution of the overall gas hold-up in gas-sparged tank with 1000 l work volume, equipped with two six-blade pitched turbines and a ring sparger of 0.41 m diameter. Fluid flow is calculated with a turbulent k - ε two fluid model using a finite volume method. The CFD simulation results indicate that the method used is suitable for the prediction of the change of overall gas hold-up with increasing both of the impeller speed and the gas flow rate.
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    Numerical simulation of bubble breakup and coalescence in bubbling two-phase flow
    (2018-01-01) Moutafchieva D.; Iliev V.
    The aim of the present work is to study the behavior of gas-liquid bubbly flow by means of Computational Fluid Dynamics (CFX ANSYS). The population balance approach taking into account the bubble coalescence and breakup in turbulent gas-liquid dispersion is included.The Euler-Euler approach and the standard k-ε mixture turbulence model in three-dimensional computational domains accounting the effect of turbulence are used to simulate the two phase flows of the bubble column.The bubble size distribution along the column height, the gas volume fraction and liquid velocity have been predicted for the two-phase systems and for liquids different from water(ethanol, glycerol). The results of nonuniform bubbles size distribution in dispersed flow are presented grouped into individual size fractions at varying initial conditions and density of the elementary mesh.