An investigation of venturi and coanda effects in blown film cooling / V. Sidiropoulos in INTERNATIONAL POLYMER PROCESSING, Vol. XV, N° 1 (03/2000)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XV, N° 1 (03/2000) . - p. 40-45 Titre : An investigation of venturi and coanda effects in blown film cooling Type de document : texte imprimé Auteurs : V. Sidiropoulos, Auteur ; J. Vlachopoulos, Auteur Année de publication : 2000 Article en page(s) : p. 40-45 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : Numerical simulation of turbulent air flow tangentially impinging on a blown film bubble has been carried out. The cooling air is assumed to originate from a dual orifice adjustable air-ring. The stream line pattern and heat flux are determined through a finite volume numerical technique using a version of the so called k-ε modeling. It is shown that as the air flows through the air ring passage relatively large under-pressure is created (Venturi effect), which applies a suction to the bubble. Depending on the flow rates and geometrical configurations the air jet may attach itself (Coanda effect) to either the air ring surface and/or to the bubble. The Coanda effect has a significant influence on local heat flux. The numerical results suggest that the Venturi and Coanda effects influence significantly process stability, production rate and final film properties. DOI : 10.3139/217.1575 En ligne : https://drive.google.com/file/d/1z8QmfewGlNE_m5c46tQQpGoL6uAEsjXs/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=16072 [article]

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Computer flow simulation of moffatt eddies in single screw extrusion / N. D. Polychronopoulos in INTERNATIONAL POLYMER PROCESSING, Vol. XXXIII, N° 5 (11/2018)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXXIII, N° 5 (11/2018) . - p. 662-668 Titre : Computer flow simulation of moffatt eddies in single screw extrusion Type de document : texte imprimé Auteurs : N. D. Polychronopoulos, Auteur ; J. Vlachopoulos, Auteur Année de publication : 2018 Article en page(s) : p. 662-668 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Analyse des flux de matières et d'énergie Matières plastiques -- Extrusion Moffatt (Tourbillons de) Simulation par ordinateur Index. décimale : 668.4 Plastiques, vinyles Résumé : A 3D flow analysis package is used to simulate the flow phenomena in a short section of the metering zone of a single screw extruder. The assumption of stationary screw and rotating barrel is used. For sharp flight root corners, in addition to the primary flow field a secondary flow was determined in front of the root of the pushing flight and behind the root of the trailing flight, akin to what is known in the fluid mechanics literature as Moffatt eddies. Fluid particles caught in Moffatt eddy regions require travel times which are at least two orders of magnitude larger than the average residence time. This implies high probability of degradation and explains the deposits of thin carbonaceous films and gels, which have been discussed in several publications in the technical literature. The computer simulations show the existence of Moffatt eddies in the presence or absence of pressure gradients. When the screw roots have relatively wide angles no Moffatt eddies are predicted, in agreement with recommendations for good screw design practices. Note de contenu : - Problem formulation and solution procedure DOI : 10.3139/217.3574 En ligne : https://www.degruyter.com/document/doi/10.3139/217.3574/pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=31405 [article]

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