Engenharia Mecânica

URI Permanente desta comunidade

http://repositorio.ufes.br/handle/10/17620

Programa de Pós-Graduação em Engenharia Mecânica

Centro: CT
Telefone: (27) 4009 2116
URL do programa: http://www.engenhariamecanica.ufes.br/pos-graduacao/PPGEM

Navegar

Agora exibindo 1 - 20 de 301

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 influência da condição de entrada senoidal na dinâmica de golfadas na simulação de escoamento horizontal gás-líquido
(Universidade Federal do Espírito Santo, 2023-08-23) Melo, Lucca Dalvi Vargas; Ramos, Rogério; https://orcid.org/0000000344932435; http://lattes.cnpq.br/2975022316691139; http://lattes.cnpq.br/3183599723222934; Nieckele, Angela Ourivio; Siqueira, Renato do Nascimento; http://lattes.cnpq.br/9791817633014124; Rodriguez, Oscar Mauricio Hernandez; Martins, Ramon Silva
There is a latent demand for developing numerical studies regarding two-phase slug flows in several industrial sectors, such as steel and food industries, and well designs in the oil and gas industry. Among the main challenges in the numerical modeling of this regime, one can highlight the development of a boundary condition that can adequately describe the main characteristics of the slugs. In this work, experimental data was generated and compared to numerical simulations of gas-liquid flows were performed using a sinusoidal inlet boundary condition with different perturbation amplitudes and slip ratios. The performed numerical simulations evidenced a significant effect of the slip ratio on the characterization of the slugs. For the case with a slip ratio greater than one, there was an increase in the frequency of slugs with decreasing perturbation amplitudes. Moreover, volume fraction levels show significant adherence to experimental results. For the no-slip case, experimental slug frequencies are simulated within a 2% range, regardless of perturbation amplitude and axial position. Interestingly, we observe a strong dependence of the characteristics of the bubble on the axial position of analysis. Deviations of the mean bubble periods with respect to experimental results may achieve 20%, depending on the axial position and the perturbation amplitude. The results suggest a preferred longitunal region for analysis since deviations smaller than 5% were found, regardless of perturbation amplitude. These results emphasize the importance of carefully analyzing slug characteristics regarding axial position.
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 model for predicting two-phase flow patterns transitions in annulus: inclinations from horizontal to near-vertical
(Universidade Federal do Espírito Santo, 2021-12-16) Oliveira, Marciellyo Ribeiro de; Martins, Marcio Ferreira; https://orcid.org/000000023023222X; http://lattes.cnpq.br/7325983059020104; https://orcid.org/000000019948214X; http://lattes.cnpq.br/; Junior, Humberto Belich; https://orcid.org/; http://lattes.cnpq.br/3879935393431243; Morales, Rigoberto Eleazar Melgarejo; https://orcid.org/; http://lattes.cnpq.br/; Ramos, Rogerio; https://orcid.org/0000000344932435; http://lattes.cnpq.br/2975022316691139
The concomitant flow of a mixture containing two phases is a complex phenomenon. One of the reasons is that the phases` interactions depend on the variations of the operational condition imposing the formation of different flow patterns that, in its turn,
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.
A numerical and statistical approach to estimate state variables in flow-accelerated corrosion problems
(Universidade Federal do Espírito Santo, 2014-08-29) Moura, Bruno Furtado de; Macêdo, Marcelo Camargo Severo de; Silva, Wellington Betencurte da; Martins, Márcio Ferreira; Colaço, Marcelo José
Sequential Monte Carlo (SMC) or Particle Filter Methods became very popular in the last few years in the statistical and engineering communities. Such methods have been widely used to deal with sequential Bayesian inference problems in several fields. SMC Methods are an approximation of sequences of probability distributions of interest, using a large set of random samples, named particles there are propagated along time with a simple Sampling Importance distribution, SI, and re-sampling techniques as well. In this work we applied two Bayesian filters to a state estimation problem involving the corrosion amount-time in a contraction-expansion geometry and compared with Computational Fluid Dynamics (CFD) results. The model adopted to estimate the mass losses is based on a double resistance due to the oxygen diffusion toward the wall through the hydrodynamic boundary layer and the oxide layer. Mass loss data over time is obtained from the literature as well. The main objective of this work is to discuss and compare the performance of the following filters: Sampling Importance Re-sampling Filter (SIR Filter) and Auxiliary Sampling Importance Re-sampling Filter (ASIR Filter) in estimation of the mass losses. Also, it is discussed the influence of the corrosion products. Best results in corrosion damage estimation were obtained using the ASIR Filter.
A Two-phase Flow Circuit Characterization By Pressure Drop Mechanistic Models, Image Processing Technique And Flow Pattern Mapping
(Universidade Federal do Espírito Santo, 2022-08-01) Lima, Tiago Guerzet Sardenberg; Ramos, Rogerio; https://orcid.org/0000000344932435; http://lattes.cnpq.br/2975022316691139; https://orcid.org/; http://lattes.cnpq.br/; Siqueira, Renato do Nascimento; https://orcid.org/; http://lattes.cnpq.br/9791817633014124; Nascimento, Francisco Julio do; https://orcid.org/; http://lattes.cnpq.br/; Martins, Ramon Silva; https://orcid.org/; http://lattes.cnpq.br/
abstract
Aferição do modelo VOF na caracterização de padrões de escoamento multifásico em tubulação horizontal e inclinada
(Universidade Federal do Espírito Santo, 2016-04-08) Lima, Marcel Pereira; Martins, Márcio Ferreira; Ramos, Rogério; Cruz, Daniel Onofre de Almeida; Cruz, Daniel Onofre de Almeida
This work aims to verify the performance of Volume of Fluid model on flow patterns characterization in horizontal and inclined circular cross section pipe. For this purpose it was used a 42 mm diameter tube with straight section of about 4.5 m in numerical and experimental tests of three flow patterns: slug, churn and stratified wavy. The fluids used were water and air in the respective flow rates of 4.99 m3/h and 9.97 m3/h for both slug and stratified wavy patterns, under15° upward and 15° downward respectively. However, churn pattern was performed under 3.49 m3/h of water and 19.95 m3/h of air in horizontal pipe.Volume of Fluid (VOF) multiphase flow model combined with k-Realizable turbulence model and scalable wall function were set inCFD commercial software, as well as specific parameters for temporal discretization and mesh refinement, besides spatial discretization methods consistent with the flows. The set of parametersand numerical methods were based on the literature and the mesh refinement was set according to mesh test. In order to evaluate the performance of the numerical modeling, images from experimental flow were compared to the numerical ones and the literature, giving good agreement between them
AN EXPERIMENTAL ANALYSIS OF ORIFICE PLATE WET GAS METER BY THIRD PRESSURE TAPPING FOR LIQUID LOADING ESTIMATION
(Universidade Federal do Espírito Santo, 2022-07-18) Caliman, Renan Favaro; Ramos, Rogerio; https://orcid.org/0000000344932435; http://lattes.cnpq.br/2975022316691139; https://orcid.org/; http://lattes.cnpq.br/; Martins, Marcio Ferreira; https://orcid.org/000000023023222X; http://lattes.cnpq.br/7325983059020104; Nascimento, Francisco Julio do; https://orcid.org/; http://lattes.cnpq.br/
abstract
Análise comparativa de aços ARBL usados na fabricação de tubos flexíveis para produção de petróleo no mar, em formações com baixo teor de H2S : um estudo de FPH utilizando solução de tiossulfato de sódio
(Universidade Federal do Espírito Santo, 2006-06-02) Girelli, Rosental Alves; Scandian, Cherlio; Macêdo, Marcelo Camargo Severo de; 1º membro da banca
This document is an experimental study of the Stress Corrosion Cracking (SCC) and Hydrogen Embrittlement (HE) behavior of a Brazilian high-strength low-alloy steel, in media with low content of H2S. It is intended to begin a qualification process of the material, which is already used in flexible pipes for petroleum production operations at the sea in situations where there is no H2S presence, to also act in cases where low concentration of this gas exists. A heat treatment is proposed for the resistance improvement of the material in these environments. The base for experimental results comparison was another material, a French one, which is already qualified and used in flexible pipes for sour oil (with H2S) production. Hence, three materials were tested: the original Brazilian one, without heat treatment (it is used in flexible pipes, in situations without H2S), the same material with the heat treatment suggested for the property improvement and possible use in low H2S environments and the French one (qualified material used in flexible pipes for oil production operations, in situations where the presence of H2S is a reality). The SCC Slow Strain Rate and Constant Strain techniques were used as the experimental tests and the media was an aqueous solution of NaCl with micro addictions of sodium thiosulfate (Na2S2O3), indicated to simulate corrosive environments with low concentration of H2S. Damage parameters (energy), embrittlement measurements, tensile properties and also fracture features of the specimens were evaluated at the comparative analysis of the materials.
Análise comparativa de medidor de vazão em flare por tecnologia ótica e pitometria utilizando túnel de vento
(Universidade Federal do Espírito Santo, 2012-07-25) Silva, Felipe Carvalho da; Ramos, Rogério; Loureiro, Bruno Venturini; Mattos, Márcio Coelho de; Soares, Márcio Martins
With recent discoveries by the oil industry related to the reserves in Brazilian pre-salt, flow measurement technology is being re-evaluated in view of the large CO2 concentrations found in these reserves. A technology that has accuracy levels similar to those obtained with flow meters currently used and also measures independent characteristics to the composition and thermodynamic properties of gases is optical flow measurement velocimetry (OFM). The present work is related to experimental study, comparison of the speed readings from Pitot tube flow meters and optical velocimetry. This experimental study consists of qualifying and quantifying the velocity profiles among the possible configurations of flow in the wind tunnel, proposing methodology using flow conditioners and damping of the readings obtained with the Pitot tube, and analysis of readings taken with the optical sensor to evaluate the device installation effects in the results. The results indicate that transit-time optical flow meters for medium to high speed levels, could provide readcohesive flow even in a misalignment of up to ± 5 °, although it appears in the installation manual of the manufacturer guarantees of results meter when a misalignment of at most up to ±2º. Regarding the optical sensor intrusive effect in the readings simultaneous with the Pitot tube, it is perceived, in general, from approximately Re> 2,05x105, the intrusive effect of this influence is suppressed by other effects. Finally, for a proper flow study through Pitometry in order to make the comparison with the optical flow metering and achieve satisfactory results with the Pitot tube, the use of specific devices of flow conditioning and damping of the measured values had to be made
Análise da dinâmica acoplada de um motor de indução trifásico montado sobre uma base elástica
(Universidade Federal do Espírito Santo, 2013-10-15) Ganda, Wenderson Luiz; Mattos, Márcio Coelho de; Loeffler Neto, Carlos Friedrich; Fardin, Jussara Farias; Rocha, Roger
The dynamic analysis of systems compound by electric motor and its support structure its very important, because there is an interaction between them and the mutual influence generate various phenomena during its operation. With mathematical models is possible to simulate the dynamical behavior of these systems, with the objective of represent an actual condition and to predict the system response. These answers provide information that can be applied in solutions to the problems during project stage and assist failure analysis. In recent years, the drives based in Direct Current Motors (DCM) have been gradually substituted by drives based in Alternate Current Three-phase Induction Motor (TIM). The coupled dynamic analysis of DCM and its structure base have been widely studded and the phenomena that occur modeled. The objective of this study is to analyze the systems compound by an elastic base support and a three-phase induction motor by coupled dynamic models, to identify and verify if non-linear oscillation phenomena are relevant to this type of motor.
Análise da dinâmica acoplada de uma máquina elétrica rotativa e sua estrutura de suporte
(Universidade Federal do Espírito Santo, 2004-12-22) Rocha Junior, Edmilson Bermudes; Mattos, Márcio Coelho de; Simonetti, Domingos Sávio Lyrio; Balthazar, José Manoel
It’s performed in this work the dynamics of the analyzes of a system made of a directcurrent electrical unbalanced engine, supported by an elastic structure. This kind ofsystem is seen as an non-ideal system, that is, an interaction between the engineand the electrical system. The importance of the study of problems involving thedocking of dynamics of various systems has increased through the constructivecharacteristics of the machines and its structures. It is believed that the constructivemachines tend to be more flexible and may work in higher rotations as well. Then,some phenomena that were not noticed in other generation machines can beobserved now and the use of a more complete models are necessary to explain it.On the operational side a bigger demand of the control system is made even morenecessary. The set of equations that lead the system studied in this work engine-structure is composed by the mechanical equations resulted from the Lagrangeequations and the ones from the Kirchhoff law tension. Moreover, the Runge-Kuttafivth order is used , with a variable pitch aiming at the simulation system. Finally, theanalyzes of the electrical motor arousal independence and series performance isrealized, taking into account the influence of the structure over the rotation.
Análise da influência das tensões residuais na variação do comportamento do ruído magnético de Barkhausen em arames utilizados em dutos flexíveis
(Universidade Federal do Espírito Santo, 2024-02-27) Feijó, Gabriel Fracalossi; Co-orientador1; https://orcid.org/; http://lattes.cnpq.br/; Co-orientador2; https://orcid.org/; http://lattes.cnpq.br/; Co-orientador3; https://orcid.org/; http://lattes.cnpq.br/; Co-orientador4; ID do co-orientador4; Lattes do co-orientador4; Orientador1; https://orcid.org/; http://lattes.cnpq.br/; Orientador2; https://orcid.org/; http://lattes.cnpq.br/; https://orcid.org/; http://lattes.cnpq.br/; 1º membro da banca; https://orcid.org/; http://lattes.cnpq.br/; 2º membro da banca; https://orcid.org/; http://lattes.cnpq.br/; 3º membro da banca; https://orcid.org/; http://lattes.cnpq.br/; 4º membro da banca; http://lattes.cnpq.br/; 5º membro da banca; https://orcid.org/; http://lattes.cnpq.br/; 6º membro da banca; https://orcid.org/; http://lattes.cnpq.br/; 7º membro da banca; https://orcid.org/; http://lattes.cnpq.br/
Flexible pipelines are used in the oil industry to transport oil and gas, being considered an advantageous option for the challenges encountered in the exploration of deeper areas, such as the pre-salt. These ducts are made up of different layers, including the traction reinforcement, made up of steel wires, which are responsible for resisting traction, compression and radial loads applied to this component. Due to the application of complex stress modules, their failure modes can become unpredictable, therefore, verify their integrity becomes essential. The use of electromagnetic techniques presents itself as a good method for the non-destructive evaluation of these materials. The present work aims to present information that makes it possible to understand the influence of residuals stress on the behavior of Barkhausen magnetic noise. To do this, the residuals stress in the flexible tubes will be tested and correlated with the rotational parameters of the Barkhausen magnetic noise and the envelope behavior of this same method. To this end, in the experimental stage, the residual stress will be proven, using the hole drilling method, in the direction of bending transverse, bending and 45º bending transversal. Next, the Barkhausen magnetic noise rotation test will be carried out at frequencies of 50 Hz and 125 Hz. After the experimental part, the RMS parameters and the Barkhausen magnetic noise envelope will be analyzed and correlated with the variation in residual stress. It is worth mentioning that with plastic deformation there is the development of crystalline anisotropy, which also directly influences the results collected. Note that the rotational RMS presents a more objective characterization of crystalline anisotropy, while the Barkhausen magnetic noise envelope presents a better understanding of the residual stress variation in the tested samples but is a challenge to separating the influence of residuals stress in the envelope of magnetic noise in materials that present crystalline anisotropy
Análise da influência de tratamento térmico na resistência à corrosão-erosão do aço inoxidável AISI 304
(Universidade Federal do Espírito Santo, 2008-12-18) Louzada, Dímisson Abreu; Macêdo, Marcelo Camargo Severo de; Franco, Sinésio Domingues; Bozzi, Antônio César
This work intends to evaluate the damaged caused by the erosion-corrosion process of a stainless steels AISI 304, under four microstructures conditions, used in various applications by the erosion, corrosion, and erosion-corrosion rates. With these rates it is possible to verify if there is a synergistic effect under the test conditions. For that reason, a slurry pot tester was useful. The experiments were performed at an impact of 7,5 m/s at room temperature. The abrasive particles of quartz used are in granulometric range 150 μm and an average sand concentration of 4 % wt. The corrosion and erosion-corrosion tests were performed in a solution of sodium chloride and acetic acid with 10-3 mol/l of sodium thiosulfate which is used to simulate the effect of the H2S presence. The samples obtained from dowel steel are cylindrical with 4,76 mm diameter and were weighted before and after each test. The erosion rate is in good agreement with the literature and is higher for solubility samples. The erosion rate is higher than the corrosion rate. The synergistic effect was observed for the test conditions.
Análise da influência de tratamento térmico na resistência a corrosão-erosão do aço inoxidável AISI 304
(Universidade Federal do Espírito Santo, 2008-12-18) Louzada, Dímisson Abreu; Macêdo, Marcelo Camargo Severo de; Bozzi, António Cesar; Franco, Sinésio Domingues
This work intends to evaluate the damaged caused by the erosion-corrosion process of a stainless steels AISI 304, under four microstructures conditions, used in various applications by the erosion, corrosion, and erosion-corrosion rates. With these rates it is possible to verify if there is a synergistic effect under the test conditions. For that reason, a slurry pot tester was useful. The experiments were performed at an impact of 7,5 m/s at room temperature. The abrasive particles of quartz used are in granulometric range 150 µm and an average sand concentration of 4 % wt. The corrosion and erosion-corrosion tests were performed in a solution of sodium chloride and acetic acid with 10-3 mol/l of sodium thiosulfate which is used to simulate the effect of the H2S presence. The samples obtained from dowel steel are cylindrical with 4,76 mm diameter and were weighted before and after each test. The erosion rate is in good agreement with the literature and is higher for solubility samples. The erosion rate is higher than the corrosion rate. The synergistic effect was observed for the test conditions.
Análise da tensão limite de escoamento em emulsões A/O de petróleo parafínico
(Universidade Federal do Espírito Santo, 2017-05-26) Vargas, Gabriel Gomes; Thompson, Roney Leon; Soares, Edson José; Campos, Flavio Barboza; Pereira, Fabio de Assis Ressel
Non-Newtonian fluids formed by dispersions, such as emulsions, solutions and gels,may exhibit viscoelastic, viscoplastic and thixotropic characteristics. When a waxycrude oil is subjected to low temperatures, its paraffin crystals precipitated, giving riseto a resistant structure. The understanding of this behavior at this critical condition isessential to analyze the restart of production in oil wells and pipelines after a produc-tion shutdown. The dimensioning of equipment used in the starting of these systemsdepends fundamentally on the yield stress of the oil in production. The dependence ofthe rheological characteristics of petroleum with the history of shear and temperaturemakes rheological evaluations complex, sometimes imprecise and with low repeatabi-lity. In this work the analyzes were conducted in a commercial type rheometer (HaakeMars III), using plate-plate geometry. Evidence indicates that the initial oil preheatingtemperature is an important variable in the rheological behavior of the fluid. The resultsindicate that the initial increase in temperature causes a severe increase in yield stressup to80◦C, above this temperature there is a dramatic reversal in the yield stress in thetwo oils studied. It is also shown the variation of the yield stress with the change of thecooling rate that the oil is exposed and an analysis of the evaporation and loss of vo-latiles. In the complex study of emulsions, droplet size distribution measurements andmorphological studies were performed. Important considerations are discussed herewith respect to yield stress in low water cut emulsions and high water cut emulsions.Finally, a model is presented for checking the rheological parameters.Keywords: Yield stress, waxy crude oil, Emulsion.
Análise da valência do Mn e Re nos compostos cerâmicos Ca2MnReO6 e Ca1,9Y0,1 MnReO6
(Universidade Federal do Espírito Santo, 2014-04-15) Cavichini, Arthur Sant'Ana; Orlando, Marcos Tadeu D'Azeredo; Depianti, Janaina Bastos; Rossi, Jesualdo Luiz; Passamai Junior, José Luis
In this work the analysis of the valences of the rhenium and manganese was undertaken in cera-mic compounds Ca2MnReO6and Ca1.9Y0.1MnReO6using the model of valence bond. For thecalculations of distances got bonds were used by Rietveld refinement from diffraction patternsof X-rays were considered that both sites have mixed valence. The calculations for the valencemodel were performed using parameters taken from the literature. For the calculations of Re6+,was proposed parameter𝑅0= 1.93Å and for Re5+the parameters𝑅0= 1.90Å and𝑅0= 1.92Å. The results valence that best set were used to calculate the occupation factor of Re6+andRe5+at the site of rhenium, and Mn2+and Mn3+in site of manganese, as well as for calcula-ting the average valence at each site. These results were compared with the results obtained byanalyzing the valence of X-ray absorption on Mn K edge and Re L3edge. After comparison, itwas concluded that the valences of Mn and Re presents in ceramic Ca2MnReO6are+2.3±0.3and+5.6±0.3with occupation factors of68%of Mn2+ions, and32%of Mn3+ions, and61%of Re6+ion and39%of Re5+ions. The results for compound Ca1.9Y0.1MnReO6to the valencesof the rhenium were few contradictory, which led us to review the results obtained by X-ray ab-sorption. Upon review, we conclude that the valence that best fits the compound is+2.2±0.3for Mn and+5.2±0.3for Re, shown a occupancy of80%of Mn2+and20%of Mn3+on thesite of manganese, and occupancy of25%to Re6+and75%to Re5+to the rhenium site
Análise da variabilidade induzida pela concentração de co2 nas leituras de medidores de vazão ultrassônicos para gás de queima
(Universidade Federal do Espírito Santo, 2016-04-29) Barros, Weverton Ferreira; Ramos, Rogério; Guidolini , Icaro Pianca; Rezende, Luiz Augusto; Martins, Marcio Ferreira
The produced effect by the attenuating character of the carbon dioxide on the ultrasonic flowmeter performance in gas flare application was verified. For this, experiments were conducted in wind tunnel with Reynolds number at 104. The results indicates that the ultrasonic meter presented measurement failures in stages of abrupt variation of this gas and whose concentration was show higher of 5%, also being verified that an approximation of the transducers tend to reduce this failures of measurement
Análise de difusividade térmica em aço duplex UNS S32304 submetido a diferentes processos de soldagem TIG e tratamento térmico
(Universidade Federal do Espírito Santo, 2016-05-13) Bolsanello, Marilia Fernandes; Passos, Carlos Augusto Cardoso; Orlando, Marcos Tadeu D'Azeredo; Macêdo, Marcelo Camargo Severo de; Rossi, Jesualdo Luiz; Passamai Junior, José Luis
Thermal diffusivity of UNS S32304 stainless steel was evaluated with the purpose ofaggregate knowledge to the development of the radioactive material transportation containment receptacles project.The Flash Lased Method was used, which is based on unidimensional thermal diffusivity equation analytical solution. A carbon dioxide laser with Gaussian profile was used, with 10−6𝑚wavelength, 10√2𝑊𝑚2⁄intensity and 10√2𝑊𝑚2⁄diameter.A sample of material was analyzed as received, in order toobtain a reference diffusivity value, and to compare with the value provided by the supplier, which ensured the method effectiveness. Thereafter, a sample welded by TIG autogenous process, with argon shield gas, was tested to analyze the welding process influence under thermal diffusivity. A sample welded by the same procedure, but heat treated under 600 °C for 8 hours and cooled by air was also analyzed, to evaluate the effect of these steels exposure to high temperatures after welding. To do so, in both welded samples, points with variable distance to sample middle were taken, including molted zone, heat affected zone and base metal. Finally, obtained results were compared to previous optical microscopy, ray X diffraction characterization, micro hardness and residual stresses analysis. It could be observed that thermal diffusivity was affected not only by welding process but also by heat treatment. Most of the points presented reduced thermal diffusivity, assigned to a material thermal conductive reduction, harmful for the use in question, once it will respond slowly to thermal changes. The heat treated sample presented diffusivity values closer to the material as received, qualitative similar results were also observed on residual stresses tests, where thermal treatment equalized materials stress state. Besides that, the molting zone point, at the sample only welded, presented a thermal diffusivity value above the one founded at base metal, which can be related to structural changes caused by heating. Nevertheless, those are partial conclusions, reinforcing the need of deeper studies concerning stainless steel UNS S32304 thermal diffusivity.

Navegar

Navegando Engenharia Mecânica por Título

Resultados por página

Opções de Ordenação