CFD simulations of dense solid–liquid suspensions in baffled stirred tanks: Prediction of the minimum impeller speed for complete suspension
| Autor: | Andrea Cipollina, Giorgio Micale, Alberto Brucato, Michele Ciofalo, Alessandro Tamburini |
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| Přispěvatelé: | Tamburini, A, Cipollina, A, Micale, G, Brucato, A, Ciofalo, M |
| Rok vydání: | 2012 |
| Předmět: |
Settore ING-IND/26 - Teoria Dello Sviluppo Dei Processi Chimici
Work (thermodynamics) Engineering business.industry Settore ING-IND/25 - Impianti Chimici General Chemical Engineering Mixing (process engineering) Mechanical engineering General Chemistry Mechanics Stirred tank Multi-fluid model Computational fluid dynamics Solid–liquid two-phase flow Complete suspension speed Sufficient suspension speed Unsuspended solids criterion Computational fluid dynamics Industrial and Manufacturing Engineering Control volume Impeller Environmental Chemistry Suspension (vehicle) Reynolds-averaged Navier–Stokes equations business Contactor |
| Zdroj: | Chemical Engineering Journal. :234-255 |
| ISSN: | 1385-8947 |
| DOI: | 10.1016/j.cej.2012.04.044 |
| Popis: | In the literature on mechanically agitated solid–liquid systems, several methods are described to estimate the minimum impeller speed Njs at which all particles are suspended, but few studies have been devoted so far to their critical comparative assessment [67] . In the present paper, several alternative Njs prediction methods are applied to CFD results obtained for selected test cases covering a broad range of suspension conditions and impeller speeds. Results are compared with one another and with classic empirical correlations [88] . The aim of the work is to assess the adequacy of different methods for predicting Njs and, more generally, to contribute to a viable CFD-based strategy for the design of solid–liquid mixing equipment. To this purpose, transient RANS simulations using the sliding grid algorithm were carried out. An Unsuspended Solids Criterion (USC) was introduced to judge whether the solids contained in a generic control volume should be regarded as suspended or unsuspended. Based on this criterion, the concept of impeller speed for sufficient suspension, Nss, was proposed. The results suggest that it may be convenient to base the design of solid–liquid contactors on the sufficient suspension speed Nss rather than on the traditional Njs concept. |
| Databáze: | OpenAIRE |
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