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Homogeneous Suspension (homogeneous + suspension)

Distribution by Scientific Domains

Chemistry	50%

Selected Abstracts

Design of a high-efficiency hydrofoil through the use of computational fluid dynamics and multiobjective optimization

AICHE JOURNAL, Issue 7 2009
N. Spogis
Abstract A computational fluid dynamics (CFD) model is proposed, based on ANSYS-CFX tools coupled to optimization models inside the commercial optimization software modeFRONTIER in order to obtain an optimal design of a high-efficiency impeller for solids suspension. The analysis of impeller shape performance was carried out using the shear-stress transport (SST) turbulence model with streamline curvature correction. This turbulence model combined the advantages of the ,,, and ,,, models, ensuring a proper relation between turbulent stress and turbulent kinetic energy, allowing an accurate and robust prediction of the impeller blade flow separation. The multiple frames of reference and the frozen rotor frame change models were used for the rotor/stator interaction inside the mixing vessel. The optimization procedure used seven design variables, two nonlinear constraints and two objective functions. The objective functions chosen (among many other possible options) to evaluate the impeller performance were the maximum solid distribution throughout the vessel (homogeneous suspension) reflected by a low variance between local solid concentration and average solid concentration inside the vessel and the higher pumping effectiveness, which was defined as the quotient of the flow and power numbers. The first objective function searches for impeller configurations able to provide good solid suspension, since it aims to achieve homogeneous suspension. The second objective function aims to reduce power consumption for a high-pumping capacity of the impeller. These criteria were considered enough to characterize the optimized impeller. Results indicated that the optimized impeller presented an increase of the pumping impeller capacity and homogeneous solid suspension with low-power consumption, especially when compared with the PBT 45° impeller. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

On-line Determination of Aggregate Size and Morphology in Suspensions

PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 3 2004
Frédéric Gruy
Abstract Information concerning the aggregation state of fine solid particles is an important element for process control and monitoring of product quality in many applications of industrial slurries. This work deals with the application of different in-line methods to the characterization of silica aggregate size and morphology. All of these methods exploit turbidity signals, obtained by various means including: from analysis of turbidity fluctuations in homogeneous suspension and from overall turbidity decrease during particle settling. This work also presents the opportunity to report progress in morphological and optical models of small aggregates. As a result of these models, the morphological characteristics of the aggregates along with the number of their constituting particles are derived from experimental results. Similarities between the different methods are examined and discussed. [source]

Basis for optimization of in vitro exposure apparatus for health hazard evaluations of mobile communications

BIOELECTROMAGNETICS, Issue 8 2001
Frank Schönborn
Abstract The main objective of this paper is to carefully study the fields induced in flasks exposed to RF electromagnetic fields. The study focuses on the widely used 60 mm Petri dishes and rectangular T-75 flasks for the two following cases: 1) cells in homogeneous suspension and 2) cell monolayers. The dependence of the coupling and the homogeneity of the SAR distribution on frequency (0.7 GHz to 2.5 GHz), polarization (E, H and k polarizations) and the amount of medium (1.9 mm to 4.7 mm medium height) is studied. In addition, the effects of the environment, meniscus and field impedance as well as the distortion of the incident field are discussed. Based on these results, advantages and disadvantages of different fundamental designs of apparatus used in the past are compared. These are TEM cells, HF chambers, radial transmission lines (RTL), waveguides and wire patch cells. Furthermore, the major optimization parameters are identified for the development of highly optimized exposure systems, enabling the conduct of high quality experiments. Bioelectromagnetics 22:547,559, 2001. © 2001 Wiley-Liss, Inc. [source]

Centrifugal pump performance calculation for homogeneous suspensions

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2009
L. J. W. Graham
Abstract Centrifugal pumps are widely used for transporting suspensions, but their head performance is derated when non-Newtonian fluids and/or coarse solids are present. Some head deration methods are available for high viscosity Newtonian fluids, Bingham plastic fluids and for coarse solids in water. This paper presents a modification of the Hydraulic Institute head deration method that is suitable for any homogeneous non-Newtonian rheology. A modification of the Walker and Goulas method is also considered. Possible anomalous behaviour of kaolin slurries in centrifugal pumps is discussed. On utilise couramment des pompes centrifuges pour le transport de suspensions, mais le rendement de leur hauteur de charge est réduit en présence de fluides non newtoniens et/ou de solides grossiers. Certaines méthodes de réduction de la hauteur de charge sont disponibles pour les fluides newtoniens à viscosité élevée, les fluides plastiques de Bingham et les solides grossiers que l'on retrouve dans l'eau. Cet article présente une modification de la méthode de réduction de la hauteur de charge de l'Hydraulic Institute qui convient à n'importe quelle rhéologie non newtonienne homogène. Une modification de la méthode de Walker et Goulas est également envisagée. L'article traite également du comportement anomal possible des bouillies de kaolin dans les pompes centrifuges. [source]