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
 
 

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