Session 21: Particulate Systems
Chairs:
Francisco Ricardo da Cunha
Universidade de Brasília
Departamento de Engenharia Mecânica
Rubens Sampaio
Departamento de Engenharia Mecânica
PUC-RIO
A BOUNDARY INTEGRAL FORMULATION FOR COMPRESSIBLE STOKES FLOW
Francisco Ricardo Cunha{
frc@orion.enm.unb.br
Universidade de Braslia,
Departamento de Engenharia Mec^anica-FT
Campus Universit ario,
70910-900 - Braslia, DF, Brasil
Michael Loewenberg { michael@taylor.eng.yale.edu
Yale University, Department
of Chemical Engineering
New Haven, CT, 06520-8286,
USA
The interplay between viscous and surface tension and its in uence on the evolving emulsion microstructure during its expansion is fundamental to the science and technology of emulsion processing. This article describes a general boundary integral formulation for compressible Stokes ows. The approach is then applied for 3D simulations of emulsion densi cation with periodic boundary conditions that involves an uniform expansion of a viscous uid containing spherical drops on a body centered cubic lattice (BCC).
Keywords: Boundary Integral,
Compressible, Emulsion, Densi cation
Paiva, João Monney
.jmonney@demgi.estv.ipv.pt
Dep de Engenharia Mecânica
e Gestão Industrial
Esc Sup Tec Inst Politec
Viseu
Campus Politécnico
3500 Viseu Portugal
Pinho, Carlos .ctp@fe.up.pt
CEFT- Dep de Engenharia
Mecânica e Gestão Industrial
Faculdade de Engenharia
da Universidade do Porto
Rua dos Bragas 4099 Porto
Portugal
Figueiredo, Rui .rui.figueiredo@gtc.dem.uc.pt
Dep de Engenharia Mecânica
Faculdade de Ciências
e Tecnologia da Universidade de Coimbra
Largo D. Dinis 3000 Coimbra
Portugal
Experiments were performed with the purpose of studying the influence of both type and pressure drop of distributor plates, on the fluidization quality of an atmospheric fluidized bed. Three different distributor types were used: perforated perspex, metallic mesh and porous ceramic, with pressures drops ranging from 0.05 to 350 kPa, and superficial air velocities from 0.1 to 2.3 m/s. Three size ranges of silica ballotinis, 355-425, 600-710 and 850-1000 µm were used as bed material. The static bed height was set to 300 mm and divided into 6 horizontal slices of 50 mm high each. For each slice pressure drop values were recorded for U0/Umf ratios from 20 to 1. In order to produce a reference for the pressure drop evolution, a modified two-phase model was introduced, taking in consideration the increase in the average global porosity as well as a change of the ratio of flow through the bubbles versus the flow through the dense phase. Finally, an empirical correlation allowing the prediction of the onset of turbulence, taking in consideration the number of holes of the distributor plate, is presented.
Keywords: Fluidization, Fluidized
bed, Pressure drop, Distributor plate.
Nazareno de Pina Braga
Roberto de Freitas Neves
Célio Augusto Gomes
de Souza
Departamento de Engenharia
Química-CT/Universidade Federal do Pará-UFPA
Campus Universitário
do Guamá, Rua Augusto Corrêa, 01
66075-900 - Belém,
PA, Brasil - E-mail: celioag@ufpa.br
The production of ceramic pieces in the state of Pará has been made by a significant number of small and medium manufacturers, being important its participation in the Amazon economy. The drying of ceramics bodies is a fundamental step in the ceramic industry to obtain a final product of quality, and consequently of good commercialization. Experiments have been carried out in a forced convection type-tunnel dryer in order to investigate the influence of sand percentage in sand-clay mixtures on the drying efficiency and in the quality of ceramic materials. The sand percentage in ceramic specimen prepared with the clay-sand mixtures was 15%, by varying the diameter of the sand particles in the mixture sand-clay in the ranges of 35/42, 42/6, 65/100 and 100/150. An analysis of the lineal shrinkage is presented for all ceramic bodies submitted to drying process by analyzing the Bigot curves. For all rehearsals accomplished, after the ceramic specimen has been burnt, the quality of the final ceramic product based on the non-occurrence of trines, non-deformation, and good mechanical resistance, indicated the high performance of the drying process. In this work, there has been also calculated and analyzed the physical properties of the final ceramic product, such as: apparent porosity, absorption of water, apparent density, and tension of rupture.
Keywords: clay-sand mixture,
drying of ceramic pieces, shrinkage.
Prof.Dr.Marcio L. de Souza-Santos.
e-mail: dss@fem.unicamp.br
UNICAMP - São Paulo
State University of Campinas
Faculty of Mechanical Engineering,
Department of Energy.
Dr.Philip D. Leveson. E-mail:
philip_leveson@hotmail.com
UNICAMP - São Paulo
State University of Campinas
Faculty of Mechanical Engineering,
Department of Energy.
Sulphur dioxide emissions
from Fluidised Bed Combustors (FBCs) can be drastically reduced by in-bed
treatment with limestone or dolomite. The technique is now well established
and extensive research has been conducted in this area. Models have been
developed to express the rate of sulphur dioxide capture by limestone,
however; such models typically require a fitting
parameter in order to correlate
the predicted to the experimental data. In the present work a sulphur capture
model has been developed. The model has been implemented into the CSFB
(Comprehensive Simulator for Fluidised-Bed) which is a code used in the
simulation of industrial FBCs. The predicted and experimentally measured
sulphur dioxide emission levels showed good agreement in all cases without
the use of any fitting parameter. The model has also been used to investigate
how the structure of limestone affects its ability to absorb sulphur dioxide
within a FBC. It was found that structures, which represent geographically
young limestones, absorb sulphur dioxide at higher rates and become deactivated
at higher conversion levels than older limestone structures. Further work
is being undertaken to see if this effect could explain the discrepancies
experienced between different sulphur capture models.
Keywords: Fluidised-Bed,
Simulation, Sulphur capture, Modelling
NUMERICAL SIMULATION OF THE SOLID PARTICLES CLASSIFICATION IN HYDROCYCLONES
Juan Romero - jromero@lncc.br
Laboratório Nacional
de Computação Cientifica LNCC,
Petropolis - Rio de Janeiro
- RJ, BRASIL
Rubens Sampaio
- rsampaio@mec.puc-rio.br
Departamento de Engenharia
Mecânica-PUC-Rio
Rua Marquês de São
Vicente 225 - Gávea, 22453-900
Rio de Janeiro - RJ, BRASIL
We presented a numerical model to quantify the classification efficiency of a hydrocyclone. this model is applied to diluted solutions, where it is possible uncoupled the equations that govern the flow of the liquid and solid phases. for the characteristic flow is formed a air core that is modeled as a free surface. this interface is characterized as being of the young-laplace type and its location is calculated, besides calculating the velocity and pressure fields. the dynamics of each solid particle is calculated and its trajectory in the hydrocyclon is traced. quantifying the fraction of fed particles that leaves for the discharge for different particle sizes the selectivity curve it is built, that characterizes the efficiency of classification of a hydrocyclon. made numerical simulations and compare with the experimental data that validate the presented model.
Keywords: Hydrocyclones,
Classification, Selectivity