EE - Artigos Publicados em Periódicos
URI permanente para esta coleçãohttps://rihomolog.furg.br/handle/1/513
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15 resultados
Resultados da Pesquisa
- ItemNumerical simulation of FCC risers(2003) Souza, Jeferson Avila; Vargas, Jose Viriato Coelho; Meien, Oscar Felippe von; Martignoni, Waldir PedroThe catalytic cracking of hydrocarbons in a FCC riser is a very complex physical and chemical phenomenon, which combines a three-dimensional, three-phase fluid flow with a heterogeneous catalytic cracking kinetics. Several researchers have carried out the modeling of the problem in different ways. Depending on the main objective of the modeling it is possible to find in the literature very simple models while in other cases, when more accurate results are necessary, each equipment is normally treated separately and a set of differential and algebraic equations is written for the problem. The riser reactor is probably the most important equipment in a FCC plant. All cracking reactions and fuel formation occur during the short time (about 4-5s) that the gas oil stays in contact with the catalyst inside the riser. This work presents a simplified model to predict the, temperature and concentrations in a FCC riser reactor. A bi-dimensional fluid flow field combined with a 6 lumps kinetic model and two energy equations (catalyst and gas oil) are used to simulate the gas oil cracking process. Based on the velocity, temperature and concentration fields, it is intended, on a next step, to use the second law of thermodynamic to perform a thermodynamic optimization of the system.
- ItemModeling and simulation of industrial FCC risers(2007) Souza, Jeferson Avila; Vargas, Jose Viriato Coelho; Meien, Oscar Felippe von; Martignoni, Waldir PedroRisers are considered vital parts in Fluidized Catalytic Cracking (FCC) conversion units. It is inside the riser reactor that the heavy hydrocarbon molecules are cracked into lighter petroleum fractions such as liquified Petroleum gas (LPG) and gasoline. The FCC process is considered a key process in the world petroleum industry, since it is the main responsible for the porfitable conversion of heavy gasoil into commercial valuable products. This work presents a simplified transient model to predict the response of a FCC riser reactor, i. e., the fluid flow, temperature and concentrations of the mixture components throughout the riser and at the exit. A bi-dimensional fluid flow field combined with a 6 lumps kinetic model and two energy equations are used to model the gasoil mixture flow and cracking process inside the riser reactor. The numerical results are in good agreement with expetimental data, as a result, the model can be utilized for design, and optimization of FCC units. The simulation herein presented shows the applicability of the proposed method for the numerical simulation and control of industrial riser's units.
- ItemComputational modeling of a regular wave tank(2009) Gomes, Mateus das Neves; Olinto, Cláudio Rodrigues; Rocha, Luiz Alberto Oliveira; Souza, Jeferson Avila; Isoldi, Liércio AndréThis paper presents two different numerical methodologies to generate regular gravity waves in a wave tank. We performed numerical simulations of wave generation through the FLUENT® package, using the Volume of Fluid (VOF) multiphase model to reproduce the wave propagation in the tank. Thus it was possible to analyze two methods for generating regular waves that could be used in future work, especially in the study of devices of energy conversion from ocean waves into electrical energy.
- ItemThermal Model for Electromagnetic Launchers(2008) Zhao, Hairong; Souza, Jeferson Avila; Ordonez, Juan CarlosThis paper presents a 3D model for the determination of the temperature field in an electromagnetic launcher. The large amounts of energy that are dissipated into the structure of an electromagnetic launcher during short periods of time lead to a complicated thermal management situation. Effective thermal management strategies are necessary in order to maintain temperatures under acceptable limits. This paper constitutes an attempt to determine the temperature response of the launcher. A complete three-dimensional model has been developed. It combines rigid body movement, electromagnetic effects and heat diffusion together. The launcher consists of two parallel rectangular rails and an armature moving between them. Preliminary results show the current distribution on the rail cross-section, the localized resistive heating, and the rail transient temperature response. The simulation results are compared to prior work presented for a 2D geometry by Powell and Zielinski (2008).
- ItemModelagem computacional de um dispositivo do tipo coluna de água oscilante para a costa de Rio Grande(2009) Gomes, Mateus das Neves; Isoldi, Liércio André; Olinto, Cláudio Rodrigues; Rocha, Luiz Alberto Oliveira; Santos, Elizaldo Domingues dos; Souza, Jeferson AvilaEste trabalho apresenta a modelagem computacional de um conversor de energia das ondas do mar em energia elétrica do tipo Coluna de Água Oscilante (CAO) submetido ao clima de ondas da costa da cidade de Rio Grande. A simulação numérica foi realizada utilizando-se o pacote FLUENT® e empregando-se o modelo multifásico Volume of Fluid (VOF) na geração da onda e na interação da mesma com o conversor. O domínio computacional foi representado por um tanque de ondas acoplado ao dispositivo CAO, possibilitando analisar o seu comportamento quando sujeito a incidência de ondas regulares com características semelhantes ao clima de ondas na costa de Rio Grande. Os resultados obtidos demonstram a potencialidade da região em gerar energia elétrica a partir da energia das ondas do mar, através do conversor tipo CAO.
- ItemModelagem computacional de um dispositivo do tipo coluna de água oscilante para a costa de Rio Grande(2009) Gomes, Mateus das Neves; Isoldi, Liércio André; Olinto, Cláudio Rodrigues; Rocha, Luiz Alberto Oliveira; Santos, Elizaldo Domingues dos; Souza, Jeferson AvilaEste trabalho apresenta a modelagem computacional de um conversor de energia das ondas do mar em energia elétrica do tipo Coluna de Água Oscilante (CAO) submetido ao clima de ondas da costa da cidade de Rio Grande. A simulação numérica foi realizada utilizando-se o pacote FLUENT® e empregando-se o modelo multifásico Volume of Fluid (VOF) na geração da onda e na interação da mesma com o conversor. O domínio computacional foi representado por um tanque de ondas acoplado ao dispositivo CAO, possibilitando analisar o seu comportamento quando sujeito a incidência de ondas regulares com características semelhantes ao clima de ondas na costa de Rio Grande. Os resultados obtidos demonstram a potencialidade da região em gerar energia elétrica a partir da energia das ondas do mar, através do conversor tipo CAO.
- ItemConstructal design of solid state fermentation bioreactors(2009) Cunha, Daniele Colembergue da; Souza, Jeferson Avila; Costa, Jorge Alberto Vieira; Rocha, Luiz Alberto OliveiraConstructal Design is applied to geometric optimization of an insulated wall bioreactor. The optimization of the bioreactor geometry allows that it to operate, below a certain temperature limit, without external cooling equipment. The possibility of using less equipment shows how geometric optimization can be used as a tool for the ecologically correct management of energy. For the geometric optimization, a mathematical model that represents the solid state fermentation by Aspergillus niger is validated and used to study a column fixed bed bioreactor with fixed volume. The model is solved numerically for an insulated wall bioreactor. According to Constructal Design the shape of the bioreactor is free to change subject to volume constraint and in the pursuit of better performance. The optimal ratio between the diameter and the length of the bioreactor, i.e., the ratio which corresponds to the optimal maximum temperature equal to 35 ºC, is calculated for several inlet velocities, volumetric flow rates and inlet air temperatures.
- ItemHexahedral modular bioreactor for solid state bioprocesses(2009) Cunha, Daniele Colembergue da; Souza, Jeferson Avila; Rocha, Luiz Alberto Oliveira; Costa, Jorge Alberto VieiraThe design of a modular bioreactor for solid state fermentation is a promising development because it keeps the homogeneity of the bed at optimal levels. This study determines the optimum geometry of elementary modules of hexahedral bioreactors subjected to constant volume. The bioreactors have a square section and do not need an external cooling system, because the optimization limits the temperature of the bed to 35 C. The geometric optimization followed the Constructal principle of minimum heat resistance. The numerical simulations take into account the following parameters: inlet air temperature and velocity, and module volume. Once the elementary module has been selected, the total volume of the bioreactor can be calculated.
- ItemTwo-dimensional Control Volume Modeling of the Resin Transfer in a Porous Media with a Heterogeneous Permeability Tensor(2008) Souza, Jeferson Avila; Nava, Marcelo José Anghinoni; Rocha, Luiz Alberto Oliveira; Amico, Sandro CamposResin Transfer Molding (RTM) is a polymer composite processing technique widely used in the aeronautics and automotive sectors. This paper describes the numerical simulation of the RTM process where Darcy’s law was used for the mathematical formulation of the problem. A control volume finite element method was used for the determination of pressure gradients inside the mold, and a geometric reconstruction algorithm is used for the resin flow-front determination. Permeability of the medium was considered either a constant or a two dimensional tensor. The application was validated by direct comparison with literature data and good qualitative and quantitative agreement was obtained. The finite volume method was built to be used with a two-dimensional unstructured grid, hence allowing the analysis of complex geometries. The results showed that the proposed methodology is fully capable of predicting resin flow advancement in a multi-layer (with distinct physical properties) reinforced media.
- ItemEnergy and exergy thermodynamic analysis of a two-stage compression refrigeration system integrated with an absorption system (NH3+H2O)(2008) Corrêa, Gilberto Arejano; Prentice-Hernández, Carlos; Rocha, Luiz Alberto Oliveira; Souza, Jeferson AvilaThis work proposes an energetic and exergetic thermodynamic analysis of two refrigeration systems: one is a conventional two stages cooling system by steam compression of ammonia and the other is named integrated refrigeration system. The conventional system, used as reference, is largely employed in cooling fish industry. The integrated refrigeration system is similar to the conventional one, although it uses in the intermediate cooling, between the stages of high and low pressure, cold water in closed circuit. The cold water is supplied by ammonia-water absorption system integrated to the conventional compression system. The calorific energy supplied is obtained from waste exceeding of the fish meal production thus the energy delivered to the integrated refrigeration system is considered of zero cost. Numeric simulation is employed to compare the behavior of both systems. The results obtained in this comparison show that the integrated refrigeration system operates with a reduction of up to 19.73 % in COP. However, the integrated refrigeration system presented an increase of up to 25.57% in exergetic efficiency and 33.09% in frigorific capacity in relation to the conventional system. These results, added to the decrease of operational cost which will be quantified in a further study, will make very attractive the use of the integrated refrigeration system.