1,720,958 research outputs found
Modeling of Magnetic-Field-Assisted Fluidization: Model Development and CFD Simulation of Magnetically Stabilized Fluidized Beds
Full text linkMagnetic-field-assisted fluidization is starting to be considered as a viable alternative to standard fluidized beds for those operations (such as particle separations, filtration, adsorption) in which the solid phase can be made of magnetic particles or, alternatively, the fluidizing agent is a ferro-fluid; thus the fluid bed responds to the action of magnetic fields, and stabilized fluidization regimes can be generated.
One of the major difficulties to be tackled is the development of a predictive model capable of estimating the stabilized-to-bubbling transition velocity for a given magnetic field or, on the other hand, the magnetic field intensity required to stabilize the bed to a quiescent condition. The fluid dynamics prediction of a stabilized bed is also a challenging task at the moment.
On this basis, a very simple model for the description of MSFB was derived in this contribution starting from basic fluid dynamics and magnetodynamics equations. The model was implemented in a commercial CFD code in order to simulate the effect of the magnetic field onset on a freely bubbling fluidized bed
Analysis of the bubbling behaviour of 2-D gas solid fluidized beds part II: Comparison between experiments and numerical simulations via Digital Image Analysis Technique
No full textIn the field of gas–solid fluidization, bubbles, and all features regarding them, have a very great importance,
as they significantly affect the process performance. Numerous experimental studies on bubbles, and
their formation, evolution, and properties, have been performed in the past. These investigations appear
particularly difficult, due to the nature of these systems, since the gas phase is distributed in both the
bubble and the emulsion phase. Several experimental approaches have been developed to tackle this
study. Among these, the Digital Image Analysis Technique purposely developed in Part I of the present
work, based on the use of a video camera for monitoring the phenomenon coupled with image analysis
has been found viable and effective.
Moreover, the bubbles behaviour and characteristics have been described by means of a variety of mathematical
models. In recent years, in particular, computational fluid dynamics (CFD) tools have been found
to be very effective in providing a powerful framework through which these models can be implemented
and numerically solved.
This paper combines both experimental and computational studies, presenting the comparison, performed
by DIAT, between experimental data and relevant CFD simulations. In particular, simulations have
been performed by means of the ANSYS-CFX code. The comparison comprises the following quantities:
bed expansion, bubble hold-up, size evolution, distribution, density, aspect ratio, and bubble velocimetry
data
Analysis of the bubbling behaviour of 2-D gas solid fluidized beds - Part I Digital Image Analysis Technique
No full textBubble characteristics are very important in the design of fluidized beds because they govern hydrodynamics and efficiency of the operation
for which the bed is used. In this work, a digital image analysis technique has been developed to study the fluidization dynamics of a lab-scale two-dimensional bubbling bed. Digital image analysis may supply a great quantity of information; it is non-intrusive, capable of securing several properties simultaneously and cost effective. The image analysis method here developed allows for the simultaneous measurements of various significant bubble properties, i.e. bubble size and bubble velocity distributions, bed height and bubble-phase hold-up, by means of a purposely in-house developed software. Present results were compared with relevant literature correlations and resulted in sound agreement, thus confirming the large potential of the technique here developed
Gas-Fluidization Characteristics of Binary Mixtures of Particles in 2D Geometry
Full text linkThe bubbling behaviour of fluidized beds has been thoroughly investigated
in the last decades by means of several techniques, e.g. X-ray, Inductance, Resistance
and Impedance based techniques, PIV. In recent years, Digital Image Analysis Techniques have shown their potential for accurate and cost effectively
measurements.
Most of the work related to bubble behaviour analysis deals with Single-sized particles,
while almost all industrial equipment operates with multi-sized particles.
Although considerable work has been done in the past with focus on the analysis of the mixing-segregation behaviour and predictions of fluid dynamics regime transitions, a lack of knowledge still exists in the analysis of bubbles properties measurements for the case of polydispersed systems.
In this work, digital image analysis has been adopted to accurately measure fundamental global parameters such as bubble hold up and bed expansion as well as average bubble hold-up distribution maps or bubble size distributions in bubbling
fluidized beds of binary mixtures of particles. The experiments have been carried out at steady state conditions with binary mixtures of corundum particles, at various inlet gas velocities. This preliminary study has been performed with the aim to collect valuable data for future development of predictive models and validation
of CFD codes
Measurement of Multiphase Flow Characteristics Via Image Analysis Techniques: The Fluidization Case Study
Full text linkIn this chapter, an overview on some imaging-based experimental techniques for the analysis of complex multiphase systems is reported. In particular, some techniques aimed at the study of fluidization dynamics will be analyzed and discussed, as developed by our research grou
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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