1,720,980 research outputs found
Solution of bivariate population balance equations using the FCMOM
No full textThe FCMOM (Finite size domain Complete set of trial functions Method Of Moments) is an efficient and accurate numerical technique to solve PBE (population balance equations) and was validated for monovariate PBE [Strumendo, M.; Arastoopour, H. Solution of PBE by MOM in Finite Size Domains. Chem. Eng. Sci. 2008, 63 (10), 2624]. In the present paper, the FCMOM is extended and used to solve
bivariate PBE. In the FCMOM, the method of moments is formulated in a finite domain of the internal coordinates and the particle distribution function is represented as a truncated series expansion by a complete system of orthonormal functions. In the extension to bivariate PBE, the capabilities of the FCMOM are maintained, particularly as far as the algorithm efficiency and the accuracy in the bivariate
particle distribution function reconstruction. The FCMOM was validated with the following bivariate applications: particle growth, particle dissolution, particle aggregation, and simultaneous aggregation and growth
Solution of PBE by MOM in Finite Size Domains
No full textA new approach to solve PBE (Population Balance Equations), FCMOM (Finite size domain Complete set of trial functions Method Of Moments), is presented. The solution of the PBE is sought, instead of the [0,∞] range, in the finite interval between the minimum and maximum particle size; their evolution is tracked imposing moving boundaries conditions. After reformulating the PBE in the standard interval
[−1, 1], the size distribution function is represented as a series expansion by a complete system of orthonormal functions. Moments evolution equations are developed from the PBE in the interval [−1, 1]. The FCMOM is implemented through an efficient algorithm and provides the
solution of the PBE both in terms of the moments and in terms of the size distribution function. The FCMOM was validated with applications to particle growth (constant, linear, diffusion-controlled), simultaneous particle growth and nucleation, particle dissolution, particle aggregation
(constant, sum, product, Brownian kernels) and simultaneous particle aggregation and growth
Solution of population balance equations by the FCMOM for in-homogeneous systems
No full textThe FCMOM (finite size domain complete set of trial functions method of moments) is an efficient and
accurate numerical technique to solve monovariate and bivariate population balance equations. It was previously
formulated for homogeneous systems. In this paper, the FCMOM approach is extended to solve monovariate
population balance equations for inhomogeneous (spatially not uniform) systems. In the FCMOM, the method
of moments is formulated in a finite domain of the internal coordinates and the particle size distribution
function is represented as a truncated series expansion by a complete system of orthonormal functions. The
FCMOM is extended to inhomogeneous systems assuming that the particle-phase convective velocity is
independent of the internal variables (particle size). The method is illustrated by applications to particle diffusion
and to particle convection. In the case of particle convection, a gas-solid dilute flow in a pipe was simulated
and the FCMOM equations were coupled with the governing equations (mass and momentum balances) of
the gas phase
Simulation of methane production from hydrates by depressurization and thermal stimulation
No full textRecently methane hydrates have attracted attention due to their large quantity on the earth and their potential as a
new resource of energy. This paper describes a one-dimensional mathematical model and numerical simulation of
methane hydrate dissociation in hydrate reserves by both depressurization and thermal stimulation using a onedimensional radial flow system (axisymmetric reservoir). A moving front that separates the hydrate reserve into
two zones is included in this model. A numerical coordinate transformation method was used to solve the moving
boundary problem. The partial differential equations were discretized into ordinary differential equations using the
method of lines. Our simulations showed that the moving front location and the gas flow rate production are
strong functions of the well pressure and reservoir temperature. The impermeable boundary condition at the reservoir results in very low temperature at the moving front and the formation of ice. The formation of ice, which plugs the
pore volume for the gas to flow, should be avoided. Compared with a stationary water phase model, our simulations showed that the assumption of a stationary water phase overpredicts the location of the moving front and the
dissociation temperature at the moving front and underpredicts the gas flow rate. The thermal stimulation using
constant temperature at the well method using a single well was found to have a limited effect on gas production
compared to gas production due to depressurization
Numerical simulation of poly-dispersed systems
No full textMulti-size equations of Iddir and Arastoopour [2005] incorporated in the MFIX code were used to predict particle segregation and annular flow of particles in a riser section of a PSRI CFB. However, the multi-size approach requires a considerable amount of computational time when several particulate phases are considered. On the other hand, population balance equations account for the particle poly-dispersity, particularly in size, and the solution of the population balance equations (PBE) can be obtained by the method of moments requiring lower computational time. Recently, the FCMOM (Finite size domain Complete set of trial functions Method of Moments) was proposed (Strumendo and Arastoopour [2006]), a technique which provides efficiently (in terms of computational time) the solution of the PBE both in terms of the moments and in terms of the particle size distribution; the FCMOM was extensively validated for homogeneous systems. FCMOM was extended to non-homogeneous systems in which two dimensional flow equations are coupled with the population balance equations
Numerical simulation of methane production from a methane hydrate formation
No full textThis paper describes a one-dimensional model for hydrate dissociation in porous media by the depressurization
method. A moving boundary, which separates the total simulation zone into two zones, is used. The governing
equations consider the convective-conductive heat transfer and mass transfer in the gas and hydrate zones
together with the energy balance at the moving front. These equations were transformed into a new coordinate
system using a coordinate transformation method. The numerical method of lines was used to discretize the
governing equations after coordinate transformation. Distributions of temperature and pressure for different
well pressure and reservoir temperature are presented. The speed of the moving front and the gas production
rate were shown to be strong functions of the well pressure and the absolute permeability of the porous
media. Our simulations also showed that the assumption of stationary water phase, underpredicts gas production
and overpredicts the speed of the moving front
Population balance equations' application in rotating fluidized bed polymerization reactor
No full textGas phase olefin polymerizations are now widely achieved in fluidized bed reactors. In fluidized bed poly-olefin reactors, small catalyst particles (20–80 micron) are introduced into the
bed, and when exposed to the gas flow (monomer), polymerization occurs. At early stage of polymerization, the catalyst particles fragment into a large number of small particles then the polymer particles growcontinuously, reaching a typical size of 1000–3000 micron. A successful
analysis of this process not only should account for the kinetics of the polymerization but also should include the particles mixing and particle size distribution in the reactor.
Rotating fluidized bed reactors are the promising process to have a better control on the particle size distribution, particle separation and increasing the reactor efficiency. Due to
the high rotational acceleration (e.g. 14 “g”) that can be imposed in these kinds of reactors, our preliminary results showed that the amount of throughput, i.e. monomer flow rate, can be increased without worrying of changing the fluidization regime from well mixed condition to slugging, so the production rate and in consequence the polymerization yield will increase.
In this study the population balance approach is used to describe the evolution and growth of the particle size in gas–solid rotating fluidized bed olefin polymerization reactors along
with CFD using Fluent program. The SMM (standard method of moments) method and QMOM (quadrature method of moments) method are used to solve the population balance
equations; these are coupled with the conservation equations of mass and momentum for the gas and solid phases. Simulations have been performed with; a) constant particle growth rate and b) variable particle growth rate that is a function of polymerization reaction rate
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
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