Teses e Dissertações (BDTD USP)
URI Permanente para esta coleção
Navegar
Submissões Recentes
- ItemAnálise teórica de ciclos Rankine orgânico e projeto de bancada de testes em pequena escala(2020-07-23) Scagnolatto, GuilhermeO ciclo Rankine orgânico é apresentado como rota tecnológica com grande potencial de crescimento para recuperação de calor de baixa temperatura, em especial, para geração de eletricidade. A aplicação dessa rota tecnológica em escalas inferiores a 2 MWe e/ou a fontes térmicas de temperaturas inferiores a 200 °C confere ao ciclo Rankine orgânico vantagens sobre outras tecnologias de conversão de energia termelétrica. Para analisar o efeito que parâmetros de projeto e de operação, como o fluido de trabalho utilizado, temperaturas de condensação, de evaporação e de entrada no expansor, e presença de recuperador de calor, exercem na eficiência térmica do ciclo, um modelo analítico para cálculo da eficiência térmica de ciclos subcríticos foi desenvolvido e expandido a partir do modelo proposto por Wang et al. (2018a), que desenvolveram um modelo para ciclos saturados e superaquecidos, sem presença de recuperador de calor. O modelo proposto neste trabalho inclui os efeitos do recuperador de calor nos ciclos e das eficiências isoentrópicas da bomba e do expansor. Para validação do modelo proposto, foram consideradas temperaturas de condensação de 10 °C a 60 °C ou a 30% do valor da temperatura crítica do fluido, e temperaturas de evaporação até, no máximo, 99,5% da temperatura crítica do fluido. Foram comparados os valores de eficiência térmica obtidos pelo método analítico com os valores obtidos pela solução numérica convencional. Após a validação do modelo proposto, realizaram-se análises dos efeitos que os parâmetros de projeto e de operação mencionados exercem na eficiência térmica do ciclo, através de inspeção da ordem de grandeza das variáveis envolvidas no cálculo. Concluiu-se que o superaquecimento do fluido de trabalho não altera significativamente a eficiência térmica do ciclo quando o ciclo não possui recuperador de calor, porém pode promover aumento significativo na eficiência quando um recuperador de calor está presente; a presença de um recuperador de calor no ciclo, seja saturado, seja superaquecido, também pode promover aumento considerável na eficiência térmica do ciclo. A eficiência isoentrópica do expansor influencia mais a eficiência térmica do ciclo do que a eficiência isoentrópica da bomba, que, mesmo assim, não deve ser negligenciada. Por fim, esses resultados serviram de base para o projeto de uma bancada de testes para avaliação experimental de ciclos Rankine orgânico subcríticos, mas já preparada para operar ciclos em condições transcríticas e supercríticas.
- ItemComparação entre os processos mesofílico e termofílico para digestão anaeróbia da fração orgânica dos resíduos sólidos urbanos (FORSU)(2020-07-20) Conte, Gabriela GuerrizeO aumento da geração de resíduos sólidos associado ao processo de urbanização intensificou a preocupação mundial em relação à escassez de áreas para disposição final e a busca por novas tecnologias de tratamento. A digestão anaeróbia, também conhecida como biometanização, é uma alternativa ambientalmente adequada de tratamento para a fração orgânica dos resíduos sólidos urbanos (FORSU), produzindo biogás e digestato, que pode ser utilizado como fertilizante. Esse processo é influenciado por diversos fatores ambientais, sendo a temperatura uma das variáveis mais importantes, pois determina o balanço econômico e a performance do sistema. Nesse contexto, o objetivo desse trabalho foi avaliar e comparar a produção de biogás utilizando diferentes temperaturas, sendo elas: mesofílica a temperatura ambiente sem aquecimento, com temperatura média diária de 25 ± 2 °C (Tamb), mesofílica aquecida a 35 ± 2 °C (T35) e termofílica aquecida a 55 ± 2 °C (T55). Os experimentos foram realizados em sistema de batelada em digestores de 5 L utilizando como substrato FORSU padrão (FORSUp) e lodo granular de avícola na proporção de 1:2 gSTVsubstrato/gSTVinóculo. O inóculo avícola foi testado juntamente com outros três candidatos a inóculo em teste de Atividade Metanogênica Específica (AME), no qual obteve o melhor resultado de 0,5838 ± 0,0026 gDQOCH4.g STV-1 .d-1. O inóculo passou por uma estratégia de aclimatação e adaptação para se adequar às temperaturas de operação e ao substrato utilizado, que foram fundamentais para a estabilidade do processo. O substrato, inóculo e meios reacionais foram caracterizados a partir de análises físico-químicas, e o inóculo e digestatos quanto a morfologia dos microrganismos através de análises de microscopia óptica de contraste de fase e fluorescência. O biogás foi medido e caracterizado quanto aos teores de CH4, CO2, N2, H2 e H2S. Foram encontrados valores de produção específica de metano de 65,49; 80,34 e 150,70 NmLCH4/gSTV para os reatores Tamb, T35 e T55, respectivamente. O digestato de todos os reatores possui potencial para aplicação na agricultura, se combinado com um pós-tratamento para a estabilização completa do material.
- ItemDemand-Driven Material Requirements Planning (DDMRP) implementation impacts on Supply Chain Management strategic processes: an AHP approach(2020-07-15) Santos, Lucas Alves da SilvaSupply Chain Management (SCM) turned out to be one of the main approaches to control costs and enhance companies\' performance in competitive markets. However, despite the evolution of theory with several frameworks developed in the past decades, companies still struggle to meet customers\' need and implement effective methods to assess demand information. As result, in recent years, new methods were developed aiming to enable companies\' processes to highly dynamic environments. Among these adaptations, the Demand Driven Material Requirements Planning (DDMRP) presents itself as an alternative in order to empower companies to thrive in this new market reality. Although the subject interest has increased in the last five years, academic research are still scarce and theory is not evolving fast enough. In order to contribute to the theory development, this study evaluate the impacts that DDMRP implementation has on Lambert\'s proposed model of Supply Chain Management Processes through an AHP-based analysis. From a literature review 8 SCM processes and 42 SCM strategic sub-processes were identified a structured model using the Analytical Hierarchy Process (AHP) is proposed and applied to rank the perceived impacts in SCM processes that DDMRP implementation inflicts. The inputs for this analysis came from surveys answered by researchers and industry practitioners who are highly experienced in SCM and DDMRP. As one of the research results, a rank was developed detailing which SCM processes and subprocesses are most impacted after DDMRP implementation. Research findings indicate that Manufacturing Flow Management (MFM) and Order Fulfillment (OF) are the two most impacted SCM processes in a DDMRP implementation. It was also possible to conclude that SCM customer related processes, Customer Relationship Management (CRM) and Customer Service Management (CSM) respectively, are highly impacted but their impacts are not fully assessed by current DDMRP literature. The results can help industrial managers/practitioners and researchers to formulate short-term and long-term decision strategies regarding DDMRP implementation in order to mitigate harmful impacts on SCM processes.
- ItemDemand-driven sales and operations planning: a framework proposal(2020-07-08) Bozutti, Daniel FernandoIn a period of great technological advances and social and economic changes, the competitive environment is challenging for companies, which requires them to take actions towards flexibility, collaboration, integration, agility, velocity, traceability and cost-effective operations and supply chains. Both scholars and practitioners are employing the term Demand-Driven (DD) to characterize companies able to respond to these dynamic characteristics. Additionally, a critical process which has the aim of matching the supply with the demand is the Sales and Operations Planning (S&OP) and this process requires an updated understanding and the necessity of changes considering the new competitiveness environment, which also requires customer centricity and being driven by demand. Based on this, this thesis had the objective of proposing a framework for the Demand-Driven Sales and Operations Planning (DDS&OP). To achieve this objective two systematics literature (SLR) reviews were conducted, one for DD phenomenon and other for S&OP process. Based on both SLRs, the framework for the DDS&OP was proposed and it was modelled in BPMN. The framework considered three perspectives (strategic, tactical and operational) and the governance of the process. The framework was validated with 17 experts from different areas (scholars and practitioners from different industries) through the Fuzzy-Delphi Method. The main result of the thesis was a framework for the DDS&OP proposed upon a robust theoretical method and validated by experts. Other results were: a common definition for the DD phenomenon presented, a structuring and unifying conceptual framework for the DD phenomenon, the necessity of expansion of both vertical and horizontal consistencies for the S&OP and a list of 20 approaches that should be considered in the S&OP process for the new competitiveness environment.
- ItemInstability analysis of compressible flows over open cavities by a Jacobian-free numerical method(2020-07-01) Mathias, Marlon SproesserThe influence of the Mach number and the boundary layer thickness over the stability of Rossiter-like modes in a subsonic compressible flow over an open rectangular cavity is studied. This work describes the implementation and use of the relevant computational methods. The most straight-forward way of accessing the stability of a flow is to build the Jacobian matrix of its governing equations and to compute its eigenvalues and eigenvectors. The so called matrix forming methods explicitly compute this matrix and use numerical algorithms to solve its eigenproblem. When the flow grows more complex, the Jacobian matrix may become unfeasibly large. The algorithm implemented here is of the Jacobianfree type, which means that this matrix is not explicitly needed. Therefore, the Arnoldi iteration method is used as all it needs is the ability of multiplying the Jacobian by an arbitrary vector. The algorithm is built in a way that a call to a flow solver is equivalent to this multiplication. The development of this solver is also covered by this work, it is a DNS (Direct Numerical Solver) for the compressible Navier-Stokes equations, which means that no turbulence models are used. High numerical precision is an important requirement as small disturbances, many orders of magnitude smaller than the base flow, must be well resolved. High order spectral like differentiation methods are employed. A validation work is performed for both the DNS and the instability analysis algorithm. Finally, this code becomes a tool to access the effect of a cavity on a boundary-layer flow. Two-dimensional cases are run for various incoming boundary layer thicknesses and Mach numbers. This work focuses on Rossiter modes and the physical phenomena that cause them to be either stable or unstable. Three types of phenomena are checked for their influence in the Rossiter modes: resonance with standing waves; spatial amplification at the mixing layer; and transfer from the flow disturbances to acoustic energy. Finally, the linear stability results are compared to DNS runs, which include non-linear effects. In the current parametric space, it was concluded that the instability at the mixing layer has an important role in selecting the Rossiter modes, while the increased flow to acoustic energy transfer caused by higher Mach numbers influence the mode amplification rate. The resonance with standing waves only plays a small role in this case.