Analyzing the influence of surface renewal on diffusive mass transport in vented single-screw extruders / Christian Marschik in INTERNATIONAL POLYMER PROCESSING, Vol. XXXII, N° 3 (07/2017)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXXII, N° 3 (07/2017) . - p. 387-393 Titre : Analyzing the influence of surface renewal on diffusive mass transport in vented single-screw extruders Type de document : texte imprimé Auteurs : Christian Marschik, Auteur ; B. Löw-Baselli, Auteur ; Jürgen Miethlinger, Auteur Année de publication : 2017 Article en page(s) : p. 387-393 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Extrudeuse monovis Matières plastiques -- Extrusion Modèles numériques Rhéologie Index. décimale : 668.4 Plastiques, vinyles Résumé : We present a semi-numerical modeling approach to analyzing the role of surface renewal during bubble-free devolatilization in vented single-screw extruders. To demonstrate the significance of surface renewal in the mass transport of volatiles, we derived approximate analytical solutions for the two-dimensional circulatory flow in a partially filled screw channel, placing special emphasis on the melt pool that forms in front of the active flight. By applying the resulting velocity field to the governing conservation equation for the volatile concentration in the polymeric phase, the convective influence of the polymer flow on mass transport is taken into account. The resulting convection-diffusion equation, which is solved numerically using the finite-volume method, provides both qualitative and quantitative insights into how volatile depletion in the melt pool is related to the flow field developed. Thus, we clearly demonstrate that surface renewal improves mass transport efficiency considerably, even at very low screw speeds. Note de contenu : DEVOLATILIZATION IN VENTED SINGLE-SCREW EXTRUDERS : Mass transport in partially filled screw channels - Modeling diffusive mass transport in the melt pool - MODELING FRAMEWORK : Modeling the flow in the melt pool - Modeling diffusive mass transport in moving fluids - RESULTS AND DISCUSSION : Circulatory flow in the melt pool - Influence of surface renewal on diffusive mass transport - Influence of test parameters DOI : 10.3139/217.3373 En ligne : https://drive.google.com/file/d/1r3j9c2fG8H0VagHWgCOr3jqZyDxlzMFY/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=28840 [article]

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Balanced mixing screw for single-screw extruder / Christian Marschik in KUNSTSTOFFE INTERNATIONAL, Vol. 108, N° 6 (06-07/2018)  

[article]  inKUNSTSTOFFE INTERNATIONAL > Vol. 108, N° 6 (06-07/2018) . - p. 46-49 Titre : Balanced mixing screw for single-screw extruder : Design of mixing elements for demanding extrusion processes Type de document : texte imprimé Auteurs : Christian Marschik, Auteur ; Otto Skrabala, Auteur ; Jürgen Miethlinger Année de publication : 2018 Article en page(s) : p. 46-49 Langues : Anglais (eng) Catégories : Malaxeurs et mélangeurs Matières plastiques -- Extrusion -- Appareils et matériels Vis d'extrusion simple Index. décimale : 668.4 Plastiques, vinyles Résumé : The homogenization of the melt – for example when coloring plastic – is a fundamental prerequisite for good end product quality in extrusion. Homogeneity is determined to a large extent by the mixing section. However, a supposedly intensive mixer is not always the best choice. Note de contenu : - Variety of geometries - Result 1 - Velocity field - Result 2 - Pressure consumption - Result 3 - Dissipation - Result 4 - Distributive mixing - Result 5 - Stretching - Conclusion : Basis for new geometries - Table : lnvestigated single-screw mixer geometries : the number of flights and blocks was varied; the identical single screw no. 3 and 5 serves as the reference geometry - Fig. 1 : Investigated block-head mixers : the nominal dia-meter of the block-head mixers is 60 mm. Reference geometries 3 and 5 are identical - Fig. 2 : Velocity field of high-molecular HDPE pipe grades : a) in the axial direction, b) in the cross-section of one block, and c) in the cross-section in between two blocks - Fig. 3 : Pressure loss: influence of the number of flights per block (a) and blocks (b) - Fig. 4 : Dissipation: influence of the number of flights per block (a) and blocks (b) - Fig. 5 : Particle distribution for geometry 1: a) at the start and b) at the end of the block-head mixer - Fig. 6 : Particle distribution at the end of the block-head mixer: a) for geometry 1 and b) geometry 8 - Fig. 7 : Particle surface stretching at the end of the block-head mixers: influence of the number of flights per block and blocks En ligne : https://drive.google.com/file/d/1iyPeNsI01amr1CobMm3433IKSohAmXst/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=31030 [article]

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On the wave to successful mixing / Maximilan Frank in KUNSTSTOFFE INTERNATIONAL, Vol. 112, N° 3 (2022)  

[article]  inKUNSTSTOFFE INTERNATIONAL > Vol. 112, N° 3 (2022) . - p. 56-59 Titre : On the wave to successful mixing : New concepts for extrusion screws Type de document : texte imprimé Auteurs : Maximilan Frank, Auteur ; Marius Dörner, Auteur ; Christian Marschik, Auteur ; Volker Schöppner, Auteur Année de publication : 2022 Article en page(s) : p. 56-59 Langues : Anglais (eng) Catégories : Mélange Polyéthylène haute densité Vis d'extrusion Index. décimale : 668.4 Plastiques, vinyles Résumé : On the test stand : the University of Paderborn, Germany, investigated conventional and new concepts for extrusion screws in order to achieve higher throughputs while retaining machine sizes. The energy-transfer screws, a further development of the wave screw, scored particularly well. Note de contenu : - Mixing sequences in single-screw extrusion - Mixing quality under the microscope - The throughputs of the different screw concepts - The wave-screw : high mixing quality and large degree of freedom - Fig. 1 : Unwound channel geometry of a double-wave and an energy-transfer screw - Fig. 2 : Schematic representation of the dispersive and distributive mixing mechanisms - Fig. 3 : . Exemplary estimate of gray value distribution as a histogram (left) with thin sections belonging to barrier and energy-transfer screws at 100 rpm - Fig. 4 : Channel cut of the simulation in the melting zone of the screw - Fig. 5 : Scheme of the particle tracking method as well as extracted and triangulated particle distribution - Fig. 6 : Exemplary application of the bin counting method. Source: Paderborn University, graphic - Fig. 7 : Exemplary triangulation of point distribution by Delaunay triangulation - Fig. 8 : Qualitative comparison between the expreimentally determined thin sections at the end of the screw and the triangulated, simulatively determined particle distributions at 100 rpm - Table 1 : Comparison of the throughputs of HDPE achieved by the different screw concepts given completely melted polymer flow En ligne : https://drive.google.com/file/d/1Fa6A114bSqKEbTBnnReH2V8Xlz7s0n5q/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=37716 [article]

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