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

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    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.
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    Modelagem transiente geral adimensional para reatores de combustão smoldering
    (Universidade Federal do Espírito Santo, 2025-11-28) Riguetti, Ruan Schultz; Co-orientador1; https://orcid.org; https://lattes.cnpq.br; Orientador1; https://orcid.org/; https://lattes.cnpq.br; https://orcid.org/; https://lattes.cnpq.br; 1º membro da banca; https://orcid.org; https://lattes.cnpq.br; 2º membro da banca; https://orcid.org; https://lattes.cnpq.br; 3º membro da banca; https://orcid.org; https://lattes.cnpq.br; 4º membro da banca; https://orcid.org; https://lattes.cnpq.br
    Smoldering combustion is a slow, flameless process that occurs at relatively low temperatures and reaction rates, typically under limited oxygen conditions. Beyond its scientific interest, this process offers environmental, technological, and social benefits, which make it relevant for both industrial applications and sustainable development. In this context, the present research develops and applies a general dimensionless numerical model for smoldering combustion reactors, aiming to simulate the phenomenon on a small scale. The approach relies on a 2D axisymmetric model implemented in COMSOL Multiphysics (v5.4) using the Local Thermal Non-Equilibrium (LTNE) consideration, which allows separate treatment of the solid and fluid phases. Conservation equations for mass, momentum, energy, and species transport were implemented in a dimensionless form and enable a comprehensive and generalized analysis of the physical and chemical processes involved. Novel dimensional and dimensionless groups emerged during the non-dimensionalization process, associated with the effects of particle-bed burning and the interstitial chemical kinetic dynamics. Classical numbers such as Prandtl, Grashof, Darcy, Schmidt, and Peclet numbers also appeared. The model proposed in the methodology was validated through three case studies. The first involved combustion at the fluid–porous interface, highlighting the influence of natural convection. In this case, the model reproduced the same recirculation patterns reported in the reference study and also allowed vi investigation of how the velocity profile was distorted by these recirculations. The second case addressed the cooling of a porous bed and was used to calibrate convective heat transfer under transient conditions. The results showed that the model is capable of simulating studies without a reactive porous bed, although a maximum discrepancy of 25% was observed in the temperature profiles when comparing the simulations with the experimental data. The third case consisted of a full simulation of smoldering combustion, which included the ignition process through a heat source, propagation of the combustion front, and coupled interactions between heat and mass. This case allows analysis of solid fuel consumption over time and comparison of temperature profiles with experimental data obtained at different axial positions of the reactor. In general, the results demonstrate that the model created is capable of capturing the main behaviors with good agreement compared to the experimental data and the results from the literature. Therefore, the proposed methodology provides a reliable model that allows one to understand smoldering dynamics