Browsing by Author "Kasa, S."

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    Bubling - Intensifying Mean of Glass Melting Process and its Mathematical Modeling
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2004) Novák, J.; Kasa, S.
    The method of 3D numerical modeling by means of the CDF program Fluent has been used to study the influence of bubbling on temperature and velocity fields in a gas heated melting furnace. Bubbling presence in the furnace has proved its intensifying influence on a melting process, which was manifested by positive influencing of glass melt temperature (higher heating up ). The same positive influence of bubbling has been noticed also in case of a glass melt flow. Bubbling in the furnace has resulted in the increase of glass melt velocity and, consequently, in speeding up the reactions between non-homogeneities and the melt, as well as in quicker glass melt refining. A double-row arrangement of bubbling nozzles has appeared to be more advantageous, as it lead to the global heating up in the furnace increased by several tens degrees ( 3 0 - 6 0 ° C ) and to the increase of velocity by about 30%.
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    The Effect of Stirrers at low Re Numbers
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2004) Kasa, S.; Novotný, F.
    During glass melt homogenisation, the stirrers are often required to show not only the homogenisation, but also a pumping effect. This effect can be achieved by means of two mechanisms. The first one is paddle uplift, applied for plane wings, airscrews, ventilation fans and turbines. This devices operates at high values of the Re number, usually 10⁵ - 10⁶ . Fig.1. The second phenomenon that can be used for pumping is a shearing force, appearing as a consequence of a drawing force which appears due to the movement of planes in a viscous liquid. Worms, extruders and feeders of various media, e.g. plastics, work on this principle. In liquids of high viscosity and with very slow movements resulting from this, inertia becomes negligible. The liquid moves only according to resultants of forces affecting at the moment. This flow is called creeping flow, or flow in Stokes' area. Worm pumps operate in this range. The mechanism of screw effect can be seen in Fig. 2. This devices operates at very low Re number e.g. for the transport of plastics polymers Re=0.006.