VINICIUS ANDREA
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Artigo IPEN-doc 26383 Knowledge base about risk and safety of nuclear facilities to support analysts and decision makers2019 - VIEIRA NETO, ANTONIO S.; OLIVA, AMAURY M.; SAUER, MARIA E.L.J.; HUNOLD, MARCOS C.; OLIVEIRA, PATRICIA da S.P.de; ANDREA, VINICIUSEpistemic uncertainty (uncertainty related to lack of knowledge), often found in the documentation of nuclear facility engineering projects, can affect the decision-making process of managers and analysts on safety and risk issues. This article conceptualizes the nature of the major uncertainties involved in engineering projects and describes a knowledge base developed in order to gather data and information related to the project of an Open-Pool Light-water Research Rector (OPLRR) and whose purpose is to assist professionals who work in the áreas of safety, design, operation, and maintenance of nuclear facilities. In order to reduce the epistemic uncertainties that may rise in the project, the OPLRR knowledge base is designed to contain a set of information that allows identifying and facilitating the forwarding of solutions to address inconsistencies, and/or pending issues that may exist in the project. In this sense, the information and the documents related to the project are organized in a graphical and hierarchical architecture, allowing the knowledge base users to quickly and easily obtain information regarding the systems, processes, equipment, and components of the Project. Besides that, a set of documents containing descriptions, reliability data and some other important information about the systems and components are specially created to the knowledge base and it is crucial to reduce epistemic uncertainties, once it raises the issues and the inconsistencies of the project, as well as it clarifies the interrelations between the systems, the functioning of the equipment, their failures modes and the consequences of their failures, and some other data, which are not originally contained in the documents of the project.Artigo IPEN-doc 25933 A reliability-based strategy for the analysis of single proton exchange membrane fuel cells2019 - OLIVEIRA, PATRICIA da S.P. de; ANDREA, VINICIUS; SANTIAGO, ELISABETE I.; LOPES, THIAGO; ANDRADE, DELVONEI A. de; LINARDI, MARCELOThe development of power conversion systems based on fuel cells has been demanding reliability studies since the requirements associated with cost and durability of these technological products have become fundamental to their acceptance by the energy market. The experimental part of the reliability study presented in this work consisted of performing life tests with single proton exchange membrane fuel cells (PEMFCs). The proposed reliability analysis methodology covered the application of qualitative and quantitative techniques. In the qualitative approach, a Failure Mode and Effect Analysis was developed in order to identify and evaluate all potential failures associated with the operation of fuel cells. In the quantitative approach, a statistical analysis was applied to the sample data generated in long-term steady-state tests of these devices. A two-parameter exponential distribution was fitted to data and the maximum likelihood estimate for the mean time to failure (MTTF) of the fuel cells was calculated. It is important to point out that the tests performed under the scope of this study were the first long-term experiments performed with the fuel cells produced in the laboratories of IPEN-CNEN/SP, Brazil. Although the results indicated that fuel cell performance and durability were still at a level below the targets normally established for similar commercial devices, the improvement of the main components of PEMFCs has been the objective of several projects developed at the institute. Thus, the main benefit brought by this study is the proposed methodology, which can be implemented as part of a reliability growth analysis of the fuel cells and can be integrated into the design process of these devices.Resumo IPEN-doc 25569 Estudos numéricos dos processos de distribuição de água durante ensaios de durabilidade em células a combustível do tipo PEM2018 - SANTIAGO, ELISABETE I.; SPRANDEL, LEOPOLDO; ANDREA, VINICIUS; CUNHA, EDGAR F.; ROBALINHO, ERIC; LINARDI, MARCELO; KORKISCHKO, IVANAs células a combustível estão entre as tecnologias mais promissoras, visto que estes dispositivos podem produzir energia elétrica com baixa emissão de poluentes e de forma muito eficiente [1]. O entendimento dos mecanismos de transporte de água em células a combustível do tipo PEM é um ponto chave para a definição de estratégias de gerenciamento de água e aumento de desempenho. Quantidade suficiente de água deve estar presente na célula para manter a condutividade protônica da membrana polimérica, no entanto, o excesso de água nas camadas porosas são as principais causas de perdas reversíveis [2]. Este estudo tem como objetivo a compreensão dos fenômenos envolvidos no transporte de água em células a combustível do tipo PEM em função das condições de operação da célula e propor condições de operação que otimizem o fluxo de água, permitindo maior durabilidade desse tipo de célula a combustível. Nesse sentido, foi realizado um estudo de modelagem e simulação numérica de uma célula a combustível unitária envolvendo os fenômenos de transporte e os processos eletroquímicos. A simulação da dinâmica da água foi realizada considerando um sistema bifásico (modelos de misturas) em diferentes condições operacionais, a saber temperatura e fluxo de gases. A análise dos resultados mostrou que a 0,6V, temperatura da célula de 75oC e vazão de H2 próximo a três vezes o valor estequiométrico, a temperatura ideal de umidificação é entre 80oC e 85oC. Temperaturas de umidificação maiores podem resultar em inundações dos canais de distribuição e camadas porosas enquanto temperaturas menores podem ocasionar a desidratação da membrana. A mesma temperatura de umidificação dos gases reagentes e da célula a combustível pode ser adotada desde que o fluxo de gases reagentes seja alto o suficiente para garantir a hidratação da membrana, neste caso, seis vezes o valor estequiométrico. Os resultados confirmam a importância do arraste eletro-osmótico no balanço de água e a importância de análises bifásicas em estudos de otimização de células a combustível. O balanço de água ideal pode ser alcançado definindo adequadamente os fluxos e temperaturas de umidificação dos gases reagentes em função do potencial de operação com auxílio de modelos numéricos.Artigo IPEN-doc 22637 The impact of the operational parameters on the PEM fuel cell long-term performance2016 - ANDREA, V.; OLIVEIRA, P.S.P.; SANTIAGO, E.I.; LINARDI, M.Durability represents one of the major barriers to the progress of the Proton Exchange Membrane Fuel Cells (PEMFCs). To elucidate the degradation of these devices, it is important to understand the issues regarding the long-term operation of PEMFCs. Thus, in this work it was analyzed the influence of the operational parameters such as relative humidity, cell temperature and the reactant flow rates on the long-term performance through experiments of 500 hours at steady state. It was observed that the degree of humidification strongly influences on the long-term performance. The test which presented the lowest global loss of performance (with both irreversible and reversible losses) was the one with the temperatures of the humidifiers and cell all set as 75°C and the reactants flow rates set as 300 and 200 ml.min-1 for the H2 and O2, respectively. Therefore, the water management is a key point in order to obtain better performances in long-term operation of PEMFCs.Artigo IPEN-doc 19849 Implementation of a laboratory infrastructure for the development of reliability and durability studies of proton exchange membrane fuel cells at UIPEN-CNEN/SP2012 - ANDREA, VINICIUS; OLIVEIRA, PATRICIA da S.P. de; LINARDI, MARCELO