Doutorado em Engenharia Mecânica

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A fase oleosa e a degaseificação do CO2 na precipitação de CaCO3: implicações. modelagem, simulação numérica, validação e desenvolvimento de protótipo experimental
(Universidade Federal do Espírito Santo, 2022-11-21) Cosmo, Rafael de Paula; Soares, Edson Jose; https://orcid.org/; http://lattes.cnpq.br/4485206584533650; https://orcid.org/; http://lattes.cnpq.br/; Pereira, Fabio de Assis Ressel; https://orcid.org/; http://lattes.cnpq.br/5476118728173549; Siqueira, Renato do Nascimento; https://orcid.org/; http://lattes.cnpq.br/9791817633014124; Aldeia, Wagner; https://orcid.org/; http://lattes.cnpq.br/; Fontes, Rosane Alves; Dariva, Claudio; Junqueira, Silvio Luiz de Mello; Martins, Andre Leibsohn
abstract
A low-cost ERT system from a new perspective: performance improvement and film thickness measurements under fluid electrical conductivity variations
(Universidade Federal do Espírito Santo, 2023-08-18) Mata, Adriana Machado Malafaia da; Martins, Marcio Ferreira; https://orcid.org/000000023023222X; http://lattes.cnpq.br/7325983059020104; https://orcid.org/0000-0002-9076-456X; http://lattes.cnpq.br/2759329761747713; Guimaraes, Nubia Rosa da Silva; Demay, Miguel Burg; Moura, Bruno Furtado de; Junior, Arnaldo Gomes Leal; https://orcid.org/0000000290750619; http://lattes.cnpq.br/7246557168481527; Sepulveda, Francisco
Electrical tomography is a non-intrusive technique connecting electrodes around a system. Through voltage measurements, the conductivity in the region inside the electrodes is estimated through the Inverse Problem (IP). By utilizing advanced techniques in the calculation of PI, obtaining tomography images quickly has become a streamlined process. These features enable safety control and multiphase flow measurement with low flow interference, in multiphase flow. Eidors is consolidated software in this technique and provides real and imaginary part results. Considering only the real part (resistive effects), we can call it Electrical Resistance Tomography (ERT). Electrical tomography depends on a conductive medium and can distinguish oil and gas in water. Our line of research focused on identifying non-conductive objects in the continuous phase of water. Using a low-cost ERT acquisition system with varying conductivities, this thesis focused on data exploration and identification of variables with the most significant impact on reconstructed image quality. Most studies use tap water for testing, with conductivity up to 0.1 S/m. Oil extraction in deep waters brought the challenge of the presence of highly saline waters. Sea water can have high electrical conductivity, reaching up to 5.3 S/m, while formation water in oil extraction can have even higher values. The differential reconstruction is based on the measurement of the homogeneous tank compared with the tank with some non-conductive object. Therefore, the differential reconstruction reduces the effect of the background conductivity since the solution is the same in both measurements. However, it is possible to observe that when increasing the solution conductivity, the image reconstruction is affected. Therefore, the study of the influence of conductivity is relevant. The electrical tomography technique has the challenge of unrelated data. Because it is highly sensitive, small changes can result in unpredictable changes in the reconstructed image. Therefore, measured data may not be related to the applied tests. From the perspective of different conductivities, an analysis was proposed to assist in identifying critical variables. We identified the impact of the signal-to-noise ratio’s variance on the reconstructed image’s quality. In this way, it is possible to predict the final quality through the variance of the measurements and help in the adequate choice of techniques that propose the improvement of the images. Another challenge is that electrical tomography becomes unfeasible at high gas fractions. Alternatively, the film thickness calculation method allows using the same acquisition system. We then proposed improvements in modeling this technique with a dimensionless model to identify meaningful relationships. In this way, it was possible to validate the results using the strategy of varying the conductivity of the solution.
A novel pathway to recover hydrocarbons from polyethylene residues through the combustion-driven pyrolysis process
(Universidade Federal do Espírito Santo, 2021-02-24) Duque, João Vitor Ferreira; Martins, Marcio Ferreira; https://orcid.org/000000023023222X; http://lattes.cnpq.br/7325983059020104; https://orcid.org/0000-0001-6639-1209; http://lattes.cnpq.br/4157383685655204; Orlando, Marcos Tadeu D Azeredo; https://orcid.org/0000000283876504; http://lattes.cnpq.br/3562894103432242; Pessoa, Fernando Luiz Pellegrini; https://orcid.org/; http://lattes.cnpq.br/6669992155373315; Rocha, Ana Maura Araujo; https://orcid.org/0000-0002-9146-4104; http://lattes.cnpq.br/6136430581477315; Debenest, Gérald; https://orcid.org/0000-0002-9597-5729; Perre, Patrick Gilbert Georges; https://orcid.org/0000-0001-6822-2775
Global production of plastic materials has grown drastically, but the technologies adopted by industry and the policies of combining waste streams, collection, treatment, and disposal have not followed this rapid growth rate. Several methods of thermochemical conversion of plastic waste into useful products have been investigated in the last decades; however, in terms of energy efficiency, the search for a technique that results in the recovery of noble products from plastic wastes is still a challenge, as is the understanding of its thermal degradation behavior. Therefore, the thesis’s general objective was to develop a self-sustainable energy device that uses low-grade fuels as heat-drive to pyrolysis, perform the polyethylene waste thermal cracking, and recover an energy-dense material. The steps toward achieving these objectives were to characterize a recycled polyethylene waste to determine its molecular composition and kinetics pathway from a single-step to a multi-step perspective; to launch a novel device in which the input energy for pyrolysis is driven by a combustion front propagating in a porous matrix, at this step, a new methodology was established to obtain a longitudinal temperature profile (LTP) for reactors with temperature increasing with time; to describe quantitatively and qualitatively for the first time, the propagation of a smoldering front in annular space - through temperature in time, gas analysis, and LTP - that wraps a concentric cylinder chamber in which the heat released by the combustion front is transferred for waste conversion; and finally, to conduct experiments toward the production and recovering of an energy-dense pyrolysis product in the form of wax and to characterize the wax employing FTIR to identify the functional groups, and a detailed kinetic analysis. The research results show that the polyethylene undergoing thermal and mechanical stress in its cycle life has functional groups with long carbon chains while weakening the compounds’ bonds. The main consequence was that recycled polyethylene need less activation energy to degrade thermally, modifying the pyrolysis pathway’s chemical groups. The designed combustion-driven reactor (C-DPyR) could perform polyethylene plastic waste pyrolysis. The proposed LTP served to explore the heat inputted to the pyrolysis chamber, ratifying that a self-sustaining combustion process carried enough energy to supply pyrolysis. The index Energy Availability showed that in the worst case, it remains 11% of energy underused, and at higher thermal energies conditions, just about 5% of the energy is consumed to convert the plastics. The primary outcome was that the volume ratio energy from combustion/energy to pyrolysis could be reduced by increasing the pyrolysis chamber’s volume to convert more kg of plastic per batch. The conclusion can also be drawn that different heat inputs were used to pyrolyze the polyethylene waste, resulting in different pyrolysis products’ yields. A maximum of about 87 wt.% of wax was recovered from an experiment at low thermal energy, confirming that low-grade fuel combustion is an alternative heat source capable of pyrolyzing plastic waste. The enthalpies of the recovered products hovered around 2115 J/g, and according to FTIR results, the wax’s functional groups identified were like the ones in low-density polyethylene’s waste. Therefore, the operational conditions attained by C-DPyR were able to recover a polyethylene wax. That means the C-DPyR process has the potential benefits of feedstock recycling in plastic waste management.
CISÃO MECÂNICA DE POLÍMEROS FLEXÍVEIS NA REDUÇÃO DE ARRASTO EM ESCOAMENTOS TURBULENTOS ATRAVÉS DE CONTRAÇÕES
(Universidade Federal do Espírito Santo, 2021-06-17) Silva, Ivanor Martins da; Soares, Edson José; https://orcid.org/0000-0003-4967-4957; http://lattes.cnpq.br/4485206584533650; https://orcid.org/0000-0003-1472-5232; http://lattes.cnpq.br/5003505468745903; Siqueira, Renato do Nascimento; https://orcid.org/0000-0002-8397-8180; http://lattes.cnpq.br/9791817633014124; Thompson, Roney Leon; http://orcid.org/0000-0002-3642-0766; http://lattes.cnpq.br/4870003562574001; Andrade, Rafhael Milanezi de; https://orcid.org/0000-0002-2839-3649; http://lattes.cnpq.br/9241045307171389; Pereira, Anselmo Soeiro; https://orcid.org/0000-0001-6688-1013; http://lattes.cnpq.br/0955392858700258; Cruz, Gilmar Mompean Munhoz da; https://orcid.org/0000-0003-0131-5402
This work presents an experimental study of drag reduction (DR) in turbulent flow by addition of polymers, specifically addressing polymeric degradation in fitting pipes (abrupt contractions). There are many studies in the literature on drag reduction in pipe, however, these studies generally assess the polymeric degradation as a whole in the pipe, that is, including pump, straight pipe, bends, tees, valves and reductions, without specifically evaluating the accessory. The practical application of drag reduction in long pipelines or industrial pipes makes it interesting to investigate how important the degradation in the accessories is in relation to the straight sections. Drag reduction in pipe fittings is still a relatively poorly studied topic. The objective of this work is to evaluate the conditions in which the polymer chain breaks in turbulent flow and the parameters that influence this important phenomenon. The evaluation of polymeric degradation in abrupt contractions is done on an experimental apparatus composed of tubes in series, with an internal diameter equal to 16.5 mm. Contractions with diameter ratio of 2x1 and 1.5x1 are used. In these tests, solutions of polyethylene oxide (PEO) diluted in filtered water are used, with concentrations of 25, 50, 100 and 200 ppm on mass basis. In order to evaluate the effect of molecular weight, Mv, on drag reduction, polymers with Mv, = 1.0 x 106 , 2.0 x 106 , 5.0 x 106 e 8.0 x 106 g/mol are used. The flow is driven by a compressor and the tests are carried out at constant pressure, with Reynolds number between 70,000 and 90,000. This study also evaluates the relationship between polymeric degradation, intrinsic viscosity and molecular weight, Mv. The study shows a reduction in Mv when DR falls due to mechanical degradation of the polymer. The loss of DR efficiency is quantified here, when there is an abrupt contraction in the pipeline, and it is found that this loss is significantly greater than when there is only a straight tube. A mathematical model is proposed to describe the drag reduction coefficient, DR, as a function of four variables: number of passes, Np, concentration of polymeric solution, c, molecular weight, Mv, and geometric factor, G. The relationship between the drop in DR and the drop in molecular weight is described. Finally, the molecular weight values of the degraded solution are obtained by measuring the intrinsic viscosity, using the Mark-Houwing equation.
Comportamento em desgaste por erosão-cavitação e em ensaios por esclerometria linear da liga Stellite 250 submetida a tratamentos térmicos e termoquímico de carbonitreção a plasma
(Universidade Federal do Espírito Santo, 2023-12-04) Oliveira, Daniela Bahiense de; Bozzi, Antonio Cesar; http://lattes.cnpq.br/3017292130810807; https://orcid.org/0000-0002-6173-6316; http://lattes.cnpq.br/6977424481086523; Franco Júnior, Adonias Ribeiro; Silva, Sidney Nicodemos da; Orlando, Marcos Tadeu D Azeredo; https://orcid.org/0000000283876504; http://lattes.cnpq.br/3562894103432242; Milan, Julio Cesar Giubilei
Cobalt superalloys are widely used due to their ability to maintain their mechanical, physical and chemical properties when used at high temperatures. However, concerns about the increasing demand for cobalt, unstable prices and few suppliers, make it essential to assess the efficiency of the materials applied. In this context, the present work investigated the effect of heat treatments (solution and aging treatments) and thermochemical plasma carbonitriding on the tribological behavior of the Stellite 250 alloy. The solution treatment was carried out at 1200°C for 1,5 hours and aging at 850°C for 4,5 hours. Thermochemical treatments were carried out at 360°C and 380°C for 9 hours. For tribological characterization, scratch tests were carried out with a progressive load (2 to 20N) and cavitation erosions tests were performed during 15 hours of exposure. The cross-sectional area of the scratches was verified by 3D profilometry. The wear mechanisms of the tribological tests were analyzed by scanning electron microscopy (SEM). The result of the microstructural characterization showed that for the cast alloy, the structure is formed by coarse grains, consisting of the α and ε phases. From the heat treatments, the structure remained mixed. Under all carbonitring conditions there was formation of a double layer of S-phase, composed of an N-enriched phase (SN) and another C-enriched layer (SC). The surface hardness values observed under carbonitrided conditions are in the order of 1100-1500 HV0.01. The scratch tests results showed that plasma carbonitriding condition enabled a considerable reduction in the coefficient of friction in relation to that observed for the Stellite 250 cast alloy. The wear mechanisms were tensile cracks in carbonitrided conditions; and in heat-treated conditions: formation of slip bands on the sides and cracks. The solution treated condition and subsequently carbonitrided at 380°C (SC380) showed greater resistance to cavitation erosion wear than the Stellite 250 cast alloy. Wear mechanisms include premature damage with formation and coalescence of pits, crater formation and brittle behavior of the material due to fatigue.
DEVELOPMENT, CALIBRATION AND DEPLOYMENT OF AN ELECTRICAL RESISTANCE TOMOGRAPHY SYSTEM FOR MULTIPHASE FLOW EXPERIMENTS
(Universidade Federal do Espírito Santo, 2020-04-15) Moura, Bruno Furtado de; Martins, Marcio Ferreira; https://orcid.org/000000023023222X; http://lattes.cnpq.br/7325983059020104; https://orcid.org/; http://lattes.cnpq.br/; Silva, Wellington Betencurte da; https://orcid.org/; http://lattes.cnpq.br/6900925458823632; Dutra, Julio Cesar Sampaio; https://orcid.org/; http://lattes.cnpq.br/5331990513570911; Oliveira, Luiz Affonso Henderson Guedes de; https://orcid.org/; http://lattes.cnpq.br/; Junior, Humberto Belich; http://lattes.cnpq.br/3879935393431243; Ramos, Rogerio; https://orcid.org/0000000344932435; http://lattes.cnpq.br/2975022316691139; Sepulveda, Francisco
Electrical Impedance Tomography (EIT) is a soft-field tomography technique for imaging in industrial and medical applications. The method consists of injecting a bidirectional known current through electrodes inside a domain and measuring the subsequent v
Diagrama abrangente e desagregação da exergia : Uma proposta de sistematização generalizada da modelagem termoeconômica
(Universidade Federal do Espírito Santo, 2021-12-22) Barone, Marcelo Aiolfi; Santos, Jose Joaquim Conceicao Soares; https://orcid.org/; http://lattes.cnpq.br/6666040476009642; https://orcid.org/; http://lattes.cnpq.br/; Arrieta, Felipe Raul Ponce; https://orcid.org/; http://lattes.cnpq.br/; Ramos, Rogerio; https://orcid.org/0000000344932435; http://lattes.cnpq.br/2975022316691139; Errera, Marcelo Risso; https://orcid.org/; http://lattes.cnpq.br/; Orrego, Daniel Alexander Florez
Thermoeconomics combines concepts of thermodynamics with economics to provide the system analyst information not available through conventional analysis. Regardless of the thermoeconomic analysis, the cost formation process is necessary, besides the defin
Dinâmica em meios setorialmente homogêneos com o método dos elementos de contorno usando as técnicas de interpolação direta e de superposição de domínios
(Universidade Federal do Espírito Santo, 2019-12-12) Barbosa, Joao Paulo; Neto, Carlos Friedrich Loeffler; https://orcid.org/0000-0002-5754-6368; http://lattes.cnpq.br/3102733972897061; https://orcid.org/; http://lattes.cnpq.br/; Santiago, Jose Antonio Fontes; https://orcid.org/0000-0003-3089-954X; http://lattes.cnpq.br/6891803842511248; Mansur, Webe Joao; https://orcid.org/0000-0001-6033-9653; http://lattes.cnpq.br/9499429606822923; Telles, Jose Claudio de Faria; https://orcid.org/; http://lattes.cnpq.br/9055052467152337; Lara, Luciano de Oliveira Castro; https://orcid.org/0000000313292957; http://lattes.cnpq.br/1675675424615229; Bulcao, Andre; Cezario, Flavio
The Domain Superposition Technique (DST) is a new alternative to the Boundary Element Method (BEM) for solving piecewise homogeneous problems where the complete domain is divided into a surrounding homogeneous domain and other complementary subdomains with different constitutive properties. In this work, the DST is coupled to the direct interpolation technique with radial basis functions (DIBEM) to solve problems governed by the Helmholtz equation, by properly transforming the domain integral, relative to the inertia of the system, into a boundary integral. Thus, we generate a dynamic model capable of calculating the natural frequency spectrum in piecewise homogeneous domains with non-regular boundaries and internal inclusions, for both two-dimensional and three-dimensional cases. In the treatment of two-dimensional problems, linear isoparametric elements are used, while in three-dimensional cases the discretization is done by flat triangular isoparametric elements, of linear variation, with multiple nodes at the edges. To assess the numerical consistency of the more general model, simpler problems such as the three-dimensional homogeneous problems governed by the Laplace and Helmholtz equations were previously examined. Piecewise homogeneous three dimensional cases governed by the Laplace Equation were solved as well, in which the DST was also applied, including examples with geometric irregularities in the contour. The methodology proposed here provides a new model based on a BEM formulation simpler and faster than the previous related formulations, with satisfactory accuracy and convergence ensured with the mesh refinement. The work is also justified considering the use of the well-known advantages of BEM, such as its greater flexibility in mesh redefinition, its natural extension to open domain cases and suitability to fracture and contact problems, provided that the computational cost in these applications is not prohibitive.
Drop rise and interfacial coalescence initiation in complex materials
(Universidade Federal do Espírito Santo, 2023-11-10) Deoclecio, Lucas Henrique Pagoto; Soares, Edson José; http://lattes.cnpq.br/4485206584533650; https://orcid.org/0000000311368380; http://lattes.cnpq.br/7292913244820007; Cunha, Francisco Ricardo da; Siqueira, Renato do Nascimento; http://lattes.cnpq.br/9791817633014124; Thompson, Roney Leon; Ramos, Rogerio; https://orcid.org/0000000344932435; http://lattes.cnpq.br/2975022316691139
Drop rise and coalescence phenomena in complex materials hold significant relevance for various environmental and industrial processes. The intricate dynamics of the sequential steps of drop rise, collision, and film drainage are influenced by non-Newtonian behaviors such as plasticity and elasticity exhibited by the surrounding material. A comprehensive understanding of these processes is crucial for the efficient design and operation of industrial mixing and separating units. However, despite their importance, the underlying mechanisms governing these phenomena are not entirely comprehended. The primary objective of this thesis is to investigate the rise and interfacial coalescence initiation of a Newtonian drop in complex materials using time-dependent direct numerical simulations. The surrounding material is progressively modeled with formulations of increasing complexity, namely, Newtonian, inelastic viscoplastic, viscoelastic, and elasto-viscoplastic. To conduct the study, the elasto-viscoplastic Saramito model is implemented and validated. The investigation focuses on elucidating the influence of plastic, elastic, inertial, viscous, and surface tension effects, as well as their interaction on the dynamics of drop rise and coalescence initiation. Initially, the entrapment condition of spherical and non-spherical drops in inelastic viscoplastic materials is assessed in terms of the ratio of the force exerted by the yield stress and the buoyancy force. It is found that when determining the force exerted by the yield stress based on the radius of the maximum cross-sectional area of the drop (normal to buoyancy), this ratio remains constant for drops with low viscosity. However, for highly viscous drops, the ratio decreases asymptotically until it reaches the limit for solid spheres. For non-spherical drops, surface tension may yield the surrounding material to minimize the surface energy of the drop, making the drop to be permanently or only temporally mobile. For elasto-viscoplastic materials, elasticity increases the level of plasticity required for entrapment. Drop rise plays an important role in the initiation of the coalescence process. Inertial effects tend to increase the drop velocity and width, while an increase in the drop’s viscosity increases viscous dissipation and slows down the drop. The influence of surface tension on the droplet velocity and width depends on the dominant forces in the flow, which can cause both an increase or decrease in these quantities. Plastic effects result in a reduction of droplet velocity and width. Drop rise in viscoelastic materials is a dynamic process, influenced by the ratio of the relaxation time of the material to the characteristic rise time of the drop. Elastic effects also contribute to a reduction in drop width, facilitating its rise. In the case of elasto-viscoplastic materials, the interplay between elastic and plastic effects gives rise to intriguing behaviors. Plastic effects enhance the elastic behavior of the material, resulting in the appearance of the negative wake and teardrop shape (both characteristic of elastic behavior) for lower values of the elastic modulus when increasing the level of plasticity. Conversely, elastic effects suppress the plastic response of the material, leading to an expanded yielded region and reduced restriction on drop mobility by plasticity with increasing levels of elasticity. Regarding the coalescence phenomenon, plasticity manifests two main effects on the film drainage process. Firstly, it induces the formation of shorter and more spherical films, and secondly, it increases the resistance of the film to flow. The effect on the film shape facilitates the film drainage process, while the effect on the resistance of the film to flow hinders it. In regimes characterized by low surface tension, the influence of plasticity on the film geometry becomes more prominent than the resistance effect, resulting in a reduction in the drainage time. Conversely, in regimes characterized by high surface tension, where the interfaces between the fluids are less deformable, the resistance effect becomes more dominant compared to the effect of film shape, leading to an increase in the drainage time with the level of plasticity. Elastic effects also contribute to the formation of shorter films, thereby facilitating the drainage process. The partial or over activation of the viscosity of the elastic material further affects the rate of film drainage. Specifically, the partial activation of viscosity increases the drainage rate, while over-activation decreases it. In the case of elasto-viscoplastic materials, plastic effects enhance the partial activation of the material’s viscosity, facilitating the initial stage of the drainage process. Additionally, elastic deformation makes it more difficult for the drainage film to freeze due to yield stress.
Estimation Problems In Advective-Diffusivereactive Phenomena Using Meshless Numerical Methods Combined With Bayesian Inference
(Universidade Federal do Espírito Santo, 2024-03-22) Dalla, Carlos Eduardo Rambalducci; Dutra, Júlio Cesar Sampaio ; https://orcid.org/0000-0001-6784-4150; http://lattes.cnpq.br/5331990513570911; Colaço, Marcelo José; https://orcid.org/0000-0002-8020-6222; http://lattes.cnpq.br/4953372732452626; Silva, Wellington Betencurte da ; https://orcid.org/0000-0003-2242-7825; http://lattes.cnpq.br/6900925458823632; https://orcid.org/0000-0002-8078-6554; http://lattes.cnpq.br/2522314513419213; Neto, Carlos Friedrich Loeffler; https://orcid.org/0000-0002-5754-6368; http://lattes.cnpq.br/3102733972897061; Lara, Luciano de Oliveira Castro ; https://orcid.org/0000-0003-1329-2957; http://lattes.cnpq.br/1675675424615229; Lamien, Bernand; https://orcid.org/0000-0003-1665-26-20; http://lattes.cnpq.br/3496682177555473; Costa, José Mir Justino da ; https://orcid.org/0000-0001-5719-4377; http://lattes.cnpq.br/2396817509327075
The mathematical modeling of advective-diffusive-reactive phenomena finds numerous applications in various scientific fields, such as the transport of pollutants and adsorption columns. Mesh reduction techniques have proven efficient and have been gaining prominence in the literature. However, despite all the progress observed, some things could be improved in dealing with complex partial differential equations. With these limitations, variations of these methods emerged and sought to deal with complex systems. The present thesis proposal involves the development of a numerical method that combines the Eulerian-Lagrangian Method (ELM) with the Method of Fundamental Solutions (MFS) to solve a series of examples modeled by the transport equation. In addition, Bayesian inference methodologies, such as particle filters, which allow the estimation of states and model parameters, will be considered, providing an inverse approach to the problem. The results contemplated the solution of benchmark cases, which have an analytical solution for evaluating the proposed method, showing accurate and stable results when tested against different Peclet numbers between 0.5-200. The method sensitivity to parameters, such as node number and positioning, was also investigated. Its performance was evaluated against metrics such as root mean squared error and absolute error. We also performed manipulations to original models to address the reaction term and extend the cases to high-dimensionalities and complex geometries using the proposed methodology.
Estudo do comportamento mecânico em soldas do aço inoxidável lean duplex UNS S32304 utilizando modelos de encruamento
(Universidade Federal do Espírito Santo, 2023-01-27) Caetano, Gabriela Aksascki; Orlando, Marcos Tadeu D Azeredo; https://orcid.org/0000000283876504; http://lattes.cnpq.br/3562894103432242; https://orcid.org/0000000333721835; http://lattes.cnpq.br/6385356041873036; Bozzi, Antônio César; https://orcid.org/0000-0003-4857-0216; http://lattes.cnpq.br/3017292130810807; Passos, Carlos Augusto Cardoso; https://orcid.org/0000-0002-6303-3569; http://lattes.cnpq.br/2528679879816545; Mucsi, Cristiano Stefano; https://orcid.org/0000-0002-8637-4999; http://lattes.cnpq.br/2583729137737338; Bezzon, Vinicius Danilo Nonato; http://lattes.cnpq.br/8711723831656721; Vieira, Estefano Aparecido
Duplex stainless steels are characterized by their weldability, corrosion resistance, and good mechanical properties, the latter two properties being due to their biphasic microstructure of ferrite and austenite. The main focus of this research was to investigate the stress-strain behavior using work hardening models of the lean duplex stainless steel UNS S32304 with a thickness of 1.8 mm, welded by autogenous TIG process followed by heat treatment at different temperatures. In addition, initial investigations were carried out with laser beam welding using powder of duplex steel with TiB2 dispersion as a filler material. Microhardness tests, metallographic characterization with stereoscopy, optical and scanning electron microscopy, tensile test, and phase quantification by image processing were performed to evaluate the specimens welded by autogenous TIG process. The metallographic analysis showed that the heat treatments after TIG welding promoted an increase in the austenite phase content. An analysis of the stress-strain curves using work hardening models showed that the Voce and Hockett-Sherby models presented goodness-of-fit with the experimental data. In addition to the research, it was demonstrated that the parameters of both models are correlated with the volumetric content of austenitic phase in the fusion zone. Furthermore, laser beam welding with powder as filler material showed complete penetration, complete melting of the powder and the sheet, and no porosity was detected. It was verified through instrumented indentation measurements the dispersion of TiB2 and increased hardness and mechanical strength of the weld.
Estudo do compósito aço/ceramico AISI-316L/Sr1,8Y0,2CrReO6 produzido através da metalurgia do pó
(Universidade Federal do Espírito Santo, 2019-06-05) Salvador, Jose Firmino; Orlando, Marcos Tadeu D Azeredo; https://orcid.org/0000000283876504; http://lattes.cnpq.br/3562894103432242; https://orcid.org/; http://lattes.cnpq.br/0061402424211214; Franco Junior, Adonias Ribeiro ; https://orcid.org/; http://lattes.cnpq.br/6677652514776940; Passamai Junior, Jose Luis ; https://orcid.org/0000-0001-6866-1460; http://lattes.cnpq.br/5445869592199028; Passos, Carlos Augusto Cardoso; https://orcid.org/2528679879816545; http://lattes.cnpq.br/2528679879816545; Vieira, Estefano Aparecido; Cavichini, Arthur Sant Ana
This work studies the sintering of a steel/ceramic composite with stainless steel AISI 316L and Sr1.8Y0.2CrReO6 double perovskite (316L/SYCRO) by powder metallurgy. The goal was to produce a material that could be used in additive manufacture with structurally impact, corrosion and magnetic properties. AISI 316L stainless steel is a corrosion resistant material, but not magnetic. Sr1.8Y0.2CrReO6 (SYCRO) ceramic shows magnetic propriety until ~360 ºC (~640 K). 90% of 316L powder was mixed with 10% of SYCRO powder. The mixture was homogenized in a ball milling at low temperature (~77 K). The obtained powder was compacted in cylindrical forms, sealed in a evacuated quartzo tube and submitted to termal treatment for sintering. As a comparative standard, samples of 316L powder were sintered as the similar way of 316L/SYCRO samples. The sintered samples were evaluated by Scanning Electron Microscopy (SEM), X-ray Powder Diffraction (XRD), X-ray Computed Microtomography, Magnetic Susceptibility and Mechanical Compression test. The 316L/SYCRO composite showed a similar magnetism of SYCRO ceramic and a diferente mechanical behavior of sintered 316L sample. Taken into account this work it was demonstrated that it is possible to produce steel/ceramic composites with controllable contents.
Estudo estrutural do compósito Fe-TiB2 obtido por spark plasma sintering
(Universidade Federal do Espírito Santo, 2023-08-21) Miranda, Mariane Gonçalves de; Orlando, Marcos Tadeu D Azeredo; https://orcid.org/0000000283876504; http://lattes.cnpq.br/3562894103432242; http://lattes.cnpq.br/2990952954091659; Rossi, Jesualdo Luiz; Passos, Carlos Augusto Cardoso; http://lattes.cnpq.br/2528679879816545; Oliveira, Marcelo Falcao de; Vieira, Estefano Aparecido
Metal matrix composites as Fe-TiB2 type have been widely investigated, since a great potential application has been identified, due to their physical and chemical properties, such as mass reduction and increased mechanical strength. Using a powder generated by the top-down technology of a microalloyed steel and a TiB2 ceramic powder, a composite with a mass ratio given by Steel (88%)/Ceramic (12%) was synthesized by the SPS (Spark Plasma Sintering) technique. The sintered samples were characterized by X-ray microtomography (μCT), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), X-ray diffraction, and transmission electron microscopy (MET). Thermodynamic simulation was also performed in order to calculate the phase transformation considering equilibrium. The high densification obtained by SPS was observed and the density reduction in relation to the matrix ρexp = 7.44(3) g/cm³. Results associated with microabrasion indicated that the presence of TiB2 promoted an increase in wear resistance of the composite in comparison to the steel. Detailed EBSD analysis revealed that the composite matrix consists of a submicrometric substructure, and combined with TEM analyses, it was possible to propose a model of the SPS sintering mechanism at the metal/ceramic interfaces.
FORMAÇÃO DE POEIRA NO EMPILHAMENTO DE MATERIAIS A GRANEL
(Universidade Federal do Espírito Santo, 2022-06-29) Leao, Rodrigo Xavier de Almeida; Junior, Humberto Belich; https://orcid.org/; http://lattes.cnpq.br/3879935393431243; https://orcid.org/; http://lattes.cnpq.br/; Mesquita, Andre Luiz Amarante; https://orcid.org/; http://lattes.cnpq.br/; Martins, Marcio Ferreira; https://orcid.org/000000023023222X; http://lattes.cnpq.br/7325983059020104; Passos, Carlos Augusto Cardoso; https://orcid.org/; http://lattes.cnpq.br/2528679879816545; Machado, Luis Paulo Silveira; Amorim, Leandro Silva
abstract
Formulações do método de elementos de contorno com interpolação direta em problemas difusivo-advectivo-reativos estacionários
(Universidade Federal do Espírito Santo, 2023-12-15) Pinheiro, Vitor Pancieri; Loeffler Neto, Carlos Friedrich; http://lattes.cnpq.br/3102733972897061; https://orcid.org/0000-0002-0645-3620; http://lattes.cnpq.br/2723699428881346; Albuquerque, Eder Lima de; Chacaltana, Julio Tomas Aquije; https://orcid.org/0000000324886232; http://lattes.cnpq.br/9108224414966705; Lara, Luciano de Oliveira Castro; https://orcid.org/0000000313292957; http://lattes.cnpq.br/1675675424615229; Campos, Lucas Silveira; Bulcao, André
The occurrence of advective-diffusive-reactive models in the description of engineering phenomena is recurrent in different industrial areas, such as oil and gas, metallurgy, paper and cellulose, energy, pollutant dispersion, among others. In the context of the development of numerical methods capable of dealing with such models, the treatment of the advective transport term stands out, as it constitutes a relevant obstacle to the performance of most of these techniques, which significantly lose their precision with the increase in the relative magnitude of this term. There is a classic formulation of the boundary element method (BEM), which uses a Green’s solution associated with the correlated differential operator, which consistently represents only problems with a uniform velocity field, although with fewer limitations regarding the intensity of advective effects. The dual reciprocity formulation (DRBEM), proposed later, removes the restriction on the mathematical shape of the velocity field and is capable of dealing with variable hydrodynamic fields, however, with satisfactory precision only when advective effects are weak. More recently, a new technique has emerged, called direct interpolation (DIBEM), which is mainly characterized by the approximation of the entire kernel of the remaining domain integrals and by a regularization process that avoids singularities generated in the coincidence between source and field points. The robust performance of the DIBEM proposal in several relevant scalar field problems, such as Poisson, Helmholtz and wave propagation problems, underlies the interest in more systemic tests also in advective-diffusive models to determine potentialities and limitations. To this end, this thesis proposes two DIBEM formulations to approach advective-diffusive-reactive models, a classic one, as a continuation of the format already tested in other scalar field problems and an alternative proposal, which uses an approach analogous to that used in DRBEM to approximate the derivatives of the potential field. Both proposed formulations are tested and contrasted with the dual reciprocity technique as a relative reference. In general terms, the classic DIBEM formulation appears to be the most accurate and robust in cases of uniform velocity field. In cases of variable velocity field, the alternative DIBEM formulation is more accurate than the classic DIBEM and the DRBEM, concomitantly, which attests to the quality of the new formulation. Both DIBEM formulations proposed in this thesis, classic and alternative, exhibited satisfactory accuracy, and are considered reliable tools in the numerical treatment of advective-diffusive-reactive models in scenarios with moderate advective effects.
MICROESTRUTURA E TEXTURA CRISTALOGRÁFICA DOS AÇOS INOXIDÁVEIS MARTENSÍTICOS AISI 410, AISI 420 e EM 1.14116
(Universidade Federal do Espírito Santo, 2022-09-30) Moura, Ariane Neves de; Orlando, Marcos Tadeu D Azeredo; https://orcid.org/0000000283876504; http://lattes.cnpq.br/3562894103432242; https://orcid.org/; http://lattes.cnpq.br/; Fichtner, Paulo Fernando Papaleo; https://orcid.org/0000-0003-4574-2262; http://lattes.cnpq.br/3107128880946249; Rossi, Jesualdo Luiz; https://orcid.org/; http://lattes.cnpq.br/0763948174052925; Passos, Carlos Augusto Cardoso; https://orcid.org/0000-0002-6303-3569; http://lattes.cnpq.br/2528679879816545; Mucsi, Cristiano Stefano; Macedo, Marcelo Camargo Severo de; http://lattes.cnpq.br/5530638975120211
Martensitic transformation in martensitic stainless steel occurs only after the final conformation in the quenching process. Ferrite grains and Cr-rich carbides are observed in the microstructure during the hot rolling, cold rolling and annealing industrial processes. In this context, this study investigated the microstructures and textures of AISI 410, AISI 420 and EN 1.4116 stainless steels with different carbide fractions, initial grain sizes and textures after 50 % cold rolling reduction and annealing. Analysis of the experimental results showed the initial texture influenced the intensity and existence of texture gradient in the recrystallized samples. The stored energy after cold rolling and grain growth during annealing were mainly influenced by the (Cr,Fe)23C6 carbide fraction, which was identified as Cr15.58Fe7.42C6 type. Reducing initial grain size caused a change in the deformation mode to larger grain boundary constraints, weakening the {110}<001> Goss component in recrystallized textures. The recrystallized microstructures of AISI 420 and EN 1.4116 steels were heterogeneous owing to the (Cr,Fe)23C6 carbide bands in the as-received condition. In addition, the selective particle drag caused the γ- steels.
Modelagem termoeconômica generalizada e sistemática para o tratamento de resíduos e internalização de encargos ambientais em sistemas térmicos
(Universidade Federal do Espírito Santo, 2023-07-10) Faria, Pedro Rosseto de; Santos, José Joaquim Conceição Soares; https://orcid.org/0000-0003-3695-2014; http://lattes.cnpq.br/6666040476009642; https://orcid.org/0000000261503248; http://lattes.cnpq.br/5236112337927566; Reis Junior, Neyval Costa; https://orcid.org/0000000261594063; http://lattes.cnpq.br/4944106074149720; Palacio, José Carlos Escobar; https://orcid.org/0000-0001-8691-2737; http://lattes.cnpq.br/1472037977658347; Orozco, Dimas José Rúa; https://orcid.org/0000-0001-8153-989X; http://lattes.cnpq.br/3457569194994816; Ramos, Rogério; https://orcid.org/0000000344932435; http://lattes.cnpq.br/2975022316691139
Thermoeconomics originally combines Thermodynamics with Economics. Nevertheless, environmental issues can be incorporated. Despite the thermoeconomic modelling improvement and the quantity of methodologies available, topics such as waste cost allocation are still subject to criticism and can be considered important challenges to be solved for the rational and systematic inclusion of environmental charges. In many of the proposed methodologies there are subjective, incomplete, inconsistent or particular allocation criteria, which makes it difficult to define the waste cost formation process. Therefore, a generalized and systematic thermoeconomic methodology capable of treating waste and taking into account environmental issues in analyses of multiproduct systems is required. The main objective of this work is to consolidate the systematization of a methodology that is directly associated with the integration of a device that represents the environment with thermoeconomic diagrams. Models that already use this device have never been applied in thermal systems with more than one source of combustion to demonstrate the need for generalization and systematization. Still concerning the device that represents the environment, this work shows for the first time: i) how it is considered in closed-cycle thermal systems, such as steam cycles; ii) how it can be introduced in models that originally do not consider it explicitly, as in the E Model that uses exergy flows to define the thermoeconomic diagram; iii) the fundamental role it plays in the internalization of environmental charges, such as carbon credits and mitigation and environmental control devices cost; and iv) how it behaves and affects a thermoeconomic diagnosis assessment. The internalization of environmental cost exactly in the environment device systematically redistributes the costs to the other components of the system and the final products. Case studies, considering gas and steam cogeneration systems, show that the environmental device has a fundamental role in the generalized and systematic internalization of environmental charges, for instance, pollutant emissions, acquisition costs of mitigation and environmental control devices, and carbon pricing, among others. Through this internalization, it becomes feasible to assess the financial and environmental implications of emissions, foster the mitigation of greenhouse gases (GHG), and enhance the design and operation of systems.
O método dos elementos de contorno com interpolação direta aplicado à solução de problemas escalares funcionais em duas dimensões
(Universidade Federal do Espírito Santo, 2019-12-13) Barcelos, Hercules de Melo; Loeffler Neto, Carlos Friedrich ; https://orcid.org/0000-0002-5754-6368; http://lattes.cnpq.br/3102733972897061; https://orcid.org/0000-0001-6325-8429; http://lattes.cnpq.br/3388431029793400; Santiago, Jose Antonio Fontes; https://orcid.org/0000-0003-3089-954X; http://lattes.cnpq.br/6891803842511248; Mansur, Webe Joao; https://orcid.org/0000-0001-6033-9653; http://lattes.cnpq.br/9499429606822923; Telles, Jose Claudio de Faria; https://orcid.org/0000-0002-9940-4798; http://lattes.cnpq.br/9055052467152337; Lara, Luciano de Oliveira Castro; https://orcid.org/0000000313292957; http://lattes.cnpq.br/1675675424615229; Campos, Lucas Silveira; Bulcao, Andre
Recently, major challenges have emerged with the advances of modern engineering, and with this, the search for more elaborate model solutions becomes necessary. In this context, the numerical formulations to treat domain integrals present in these models
O USO DO MÉTODO DE SUPERFÍCIE DE RESPOSTA NA OTIMIZAÇÃO TERMOECONÔMICA DE SUPERESTRUTURAS MODELADAS EM SOFTWARE COMERCIAL PARA PROJETO DE SISTEMAS DE RECUPERAÇÃO DE CALOR RESIDUAL EM MOTORES DIESEL ESTACIONÁRIOS
(Universidade Federal do Espírito Santo, 2020-06-29) Araujo, Leonardo Rodrigues de; Santos, Jose Joaquim Conceicao Soares; https://orcid.org/; http://lattes.cnpq.br/6666040476009642; https://orcid.org/; http://lattes.cnpq.br/; Martins, Marcio Ferreira; https://orcid.org/000000023023222X; http://lattes.cnpq.br/7325983059020104; Rocha, Helder Roberto de Oliveira; https://orcid.org/000000016215664X; http://lattes.cnpq.br/8801325729735529; Silva, Wellington Betencurte da; https://orcid.org/; http://lattes.cnpq.br/6900925458823632; Silva, Julio Augusto Mendes da; Colaco, Marcelo Jose
In a world with finite resources of natural fuels, increased energy demand and increasing levels of environmental pollution, issues related to the thermal systems design, such as energy efficiency, cost estimation, design complexity, environmental awarene
OTIMIZAÇÃO DE SUPERESTRUTURAS PARA A RECUPERAÇÃO DE CALOR RESIDUAL DE UMA TERMELÉTRICA BRASILEIRA A MOTORES ALTERNATIVOS DE COMBUSTÃO INTERNA
(Universidade Federal do Espírito Santo, 2021-08-31) Morawski, Alexandre Persuhn; Santos, José Joaquim Conceição Soares; https://orcid.org/0000-0003-3695-2014; http://lattes.cnpq.br/6666040476009642; https://orcid.org/0000-0002-1158-3083; http://lattes.cnpq.br/0116066750864705; Carvalho, Monica; https://orcid.org/0000-0002-8524-3452; http://lattes.cnpq.br/7491245049317833; Silva, Julio Augusto Mendes da; https://orcid.org/; http://lattes.cnpq.br/3724171990188048; Lora, Electo Eduardo Silva; https://orcid.org/0000-0001-8969-3541; http://lattes.cnpq.br/5479717772667720; Ramos, Rogerio; https://orcid.org/0000000344932435; http://lattes.cnpq.br/2975022316691139; Donatelli, João Luiz Marcon; http://lattes.cnpq.br/2019757368415541
The Brazilian thermal power plants were originally designed to serve as standby energy security for the grid, which is mainly supported by hydroelectric plants. The internal combustion engine (ICE) power plants eliminate copious amounts of residual heat through exhaust gases and cooling water. The current scenario has led to an increase in the operational times of these plants. An attractive solution for increasing power and efficiency in this situation is waste heat recovery (WHR). A variety of technologies and configurations can be used for WHR. The selection of the best WHR system is not a simple task, and the solution should not be generalized for different applications. In this context, optimization approach using mathematical programming has the advantage of providing a domain-independent systematic framework. In this thesis, a superstructure method is used for structural and parametric thermoeconomic optimization, selecting the best WHR for a Brazilian ICE power plant, considering UTE Viana as case study. The specificities and uncertainties of the Brazilian electricity scenario are taken into account through different operational and economic boundary conditions. The selection of the most suitable objective function that characterize the specificities of a Brazilian power plant is analyzed, as well as the influence of these objective functions on the optimization results. Moreover, is evaluated the influence of different heat carriers and economies of scale application. Four technologies are considered: conventional Rankine cycle (CRC), organic Rankine cycle (ORC), Kalina cycle (KC), and absorption chillers for intake air cooling (ChA). The adopted objective functions are: operating profit, net power, specific cost of investment, and specific cost of the generated power. The results demonstrate that the optimization responses are highly influenced by the objective functions, especially when different types of technologies are compared. The results analysis showed that the operating profit is the most suitable objective function to WHR of Brazilian power plants, accounting the uncertainties of the Brazilian scenario by means of annual dispatch hours and variable unit cost (VUC). The ORC alternative presented the best results when maximizing the operating profit, being indicated as the best alternative for WHR of Brazilian ICE power plants. The importance of a complete and simultaneous structural and parametric thermoeconomic optimization using the superstructure method was verified with the extensive variation of the optimum synthesis and parameters of the ORC. The optimization results showed that the influence of different objective functions, operational and economic boundary conditions, heat carries and economies of scale are present both in the variation of parametric variables, as in structural variables. For an optimistic scenario of dispatch and variable unit cost of electricity, the WHR using ORC systems can increase the power plant generation capacity up to 9.4%. For a more realistic scenario of boundary conditions, using an ORC system can increase the power plant generation capacity up to 5.4%. Keywords: Superstructure. Thermoeconomic optimization. Waste heat recovery. Brazilian thermal power plants. Internal combustion engines.

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