Modelagem matemática e simulaçao em tempo real de um trocador de calor regenerador

Orientador: José Viriato C. VargasCo-orientador: Juan Carlos OrdonezDissertaçao (mestrado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduaçao em Engenharia. Defesa: Curitiba, 2005Inclui bibliografiaÁrea de concentraçao: Engenharia de Processos Térmicos e Químico

Design for Service (DFS) in the Product Development Process (PDP) / Design for Service (DFS) no Processo de Desenvolvimento de Produto (PDP)

Due to the importance and growth of the demand of new products and services, there is a constant necessity to improve business processes. However, there are different approaches from different authors regarding this subject.  In the context of Design for Service (DFS), the first and the most traditional approach among the companies is to develop the products through a Product Development Process (PDP), which fundamentally considers the product design while the services are only intuitively presented throughout the life cycle. The DFS can also be developed in a parallel manner, putting service and product together. However, there are only few methods that integrate DFS into the PDP.  Review the existing literature about the best practices of the Design for Service (DFS) that incorporate “design for service” into the Product Development Process (PDP) in order to bring a better understanding of how to implement the DFS to PDP. The focus of this work is the DFS and its best practices, constituted by a Systematic Literature Review. A Systematic Literature Review elaborated in indexed databases (Scopus, Web of Knowledge, Compendex) was used and it was complemented by exploratory searches in the literature in order to compose the bibliographic portfolio. By examining the portfolio and the selected documents, it was possible to elaborate an analysis and organize it in chronological order, creating a timeline. The results indicate a growing interest in the service area in the past years, and clarify that the period between 2006 and 2014 were the years that had the greater research activity. The results are also important because they identify what the best practices of DFS are and what the important contributions to future research that may lead to the development of a model goal to incorporate DFS into PDP.

Constructal alkaline membrane fuel cell (AMFC) design

This paper introduces a structured procedure to optimize the internal structure (relative sizes, spacing) and external shape (aspect ratios) of a single alkaline membrane fuel cell so that net power is maximized. The optimization of flow geometry is conducted for the smallest (elemental) level of a fuel cell stack, i.e., the single alkaline membrane fuel cell, which is modeled as a unidirectional flow system. The polarization curve, total and net power, and efficiency are obtained as functions of temperature, pressure, electrolyte solution concentration (KOH), geometry and operating parameters. The optimization is subjected to fixed total volume. There are two levels of optimization: (i) the internal structure, which basically accounts for the relative thicknesses of two reaction and diffusion layers and the membrane space, and (ii) the external shape, which accounts for the external aspect ratios of a square section plate that contains all single alkaline membrane fuel cell components. The available volume is distributed optimally through the system so that the net power is maximized. Temperature and pressure gradients play important roles, especially as the fuel and oxidant flow paths increase. The optimized internal structure and external shape are a result of an optimal balance between electrical power output and pumping power required to supply fuel and oxidant to the fuel cell through the gas channels. In the process, a third level of optimization was found with respect to the KOH concentration in the electrolyte solution that leads to a 3-way maximized net power output. The numerical results show that the maxima found are sharp, since a variation of up to 600% in net power was observed within the tested range of AMFC external aspect ratios, what emphasizes the importance of finding the optimal AMFC parameters, no matter how complex the actual design might be. It is also shown that the three times maximized net power increases monotonically with total volume raised to the power 0.7 (~3/4), similarly to metabolic rate and mass in animal design. Due to the fact that precision and low computational time are combined, it is expected that the model could be used as an important tool for AMFC design, control and optimization at the fuel cell stack level

Constructal alkaline membrane fuel cell (AMFC) design

This paper introduces a structured procedure to optimize the internal structure (relative sizes, spacing) and external shape (aspect ratios) of a single alkaline membrane fuel cell so that net power is maximized. The optimization of flow geometry is conducted for the smallest (elemental) level of a fuel cell stack, i.e., the single alkaline membrane fuel cell, which is modeled as a unidirectional flow system. The polarization curve, total and net power, and efficiency are obtained as functions of temperature, pressure, electrolyte solution concentration (KOH), geometry and operating parameters. The optimization is subjected to fixed total volume. There are two levels of optimization: (i) the internal structure, which basically accounts for the relative thicknesses of two reaction and diffusion layers and the membrane space, and (ii) the external shape, which accounts for the external aspect ratios of a square section plate that contains all single alkaline membrane fuel cell components. The available volume is distributed optimally through the system so that the net power is maximized. Temperature and pressure gradients play important roles, especially as the fuel and oxidant flow paths increase. The optimized internal structure and external shape are a result of an optimal balance between electrical power output and pumping power required to supply fuel and oxidant to the fuel cell through the gas channels. In the process, a third level of optimization was found with respect to the KOH concentration in the electrolyte solution that leads to a 3-way maximized net power output. The numerical results show that the maxima found are sharp, since a variation of up to 600% in net power was observed within the tested range of AMFC external aspect ratios, what emphasizes the importance of finding the optimal AMFC parameters, no matter how complex the actual design might be. It is also shown that the three times maximized net power increases monotonically with total volume raised to the power 0.7 (~3/4), similarly to metabolic rate and mass in animal design. Due to the fact that precision and low computational time are combined, it is expected that the model could be used as an important tool for AMFC design, control and optimization at the fuel cell stack level

Update on the Combined Analysis of Muon Measurements from Nine Air Shower Experiments

Over the last two decades, various experiments have measured muon densities in extensive air showers over several orders of magnitude in primary energy. While some experiments observed differences in the muon densities between simulated and experimentally measured air showers, others reported no discrepancies. We will present an update of the meta-analysis of muon measurements from nine air shower experiments, covering shower energies between a few PeV and tens of EeV and muon threshold energies from a few 100 MeV to about 10GeV. In order to compare measurements from different experiments, their energy scale was cross-calibrated and the experimental data has been compared using a universal reference scale based on air shower simulations. Above 10 PeV, we find a muon excess with respect to simulations for all hadronic interaction models, which is increasing with shower energy. For EPOS-LHC and QGSJet-II.04 the significance of the slope of the increase is analyzed in detail under different assumptions of the individual experimental uncertainties

Search for Spatial Correlations of Neutrinos with Ultra-high-energy Cosmic Rays

For several decades, the origin of ultra-high-energy cosmic rays (UHECRs) has been an unsolved question of high-energy astrophysics. One approach for solving this puzzle is to correlate UHECRs with high-energy neutrinos, since neutrinos are a direct probe of hadronic interactions of cosmic rays and are not deflected by magnetic fields. In this paper, we present three different approaches for correlating the arrival directions of neutrinos with the arrival directions of UHECRs. The neutrino data are provided by the IceCube Neutrino Observatory and ANTARES, while the UHECR data with energies above ∼50 EeV are provided by the Pierre Auger Observatory and the Telescope Array. All experiments provide increased statistics and improved reconstructions with respect to our previous results reported in 2015. The first analysis uses a high-statistics neutrino sample optimized for point-source searches to search for excesses of neutrino clustering in the vicinity of UHECR directions. The second analysis searches for an excess of UHECRs in the direction of the highest-energy neutrinos. The third analysis searches for an excess of pairs of UHECRs and highest-energy neutrinos on different angular scales. None of the analyses have found a significant excess, and previously reported overfluctuations are reduced in significance. Based on these results, we further constrain the neutrino flux spatially correlated with UHECRs

EDITORIAL

The editorial of Thermal Engineering of this issue continues the discussion on scientific research needs in vital areas in which thermal engineering has important participation. The main goal is to motivate the readers, within their specialties, to identify possible subjects for their future research. It is estimated that the existing amount of fossil fuels will last for many years. However, there is a need to look for alternative sources of energy in order to preserve the environment. De Angelis et. al., in his article, Energy Research Outlook. What to Look for in 2018 (ACS Energy Lett. 3(2018) 261-263), argues that generation and storage of technical and economically viable renewable forms of energies are the main obstacles to be overcome. In his article, De Angelis also lists some technological areas that need more research effort in the energy field: energy materials, electrochemical energy conversion and energy storage, solar cells, solar fuels, LED and display devices and, the last but not least, theory and computational modeling. Possible answers for those questions can be given from what it is called constructal theory. Constructal theory states that geometry (flow architecture) is generated by seeking the global performance subjected to global restrictions. According to the constructal law, the optimization of the flow architecture begins in a small scale (elementary level), in which, even though small, the system still keeps its identity (e.g., a brook in a river basin, a single polymer electrolyte membrane fuel cell (PEMFC) in a PEMFC stack, a cell in a multicellular organisms). The irreversibility caused by the flow resistance is minimized for a maximum global performance at the level of the complete system. Any physical system is a combination of several flow systems (e.g., electric, chemical, fluid and heat). Therefore, it can be seen that the optimization of the architecture of flow systems is as common in engineering as is in nature, where the most fit organisms (optimum configuration) survive selection (global restrictions). The mission of Thermal Engineering is to document the scientific progress in areas related to thermal engineering (e.g., energy, oil and renewable fuels). We are confident that we will continue to receive articles’ submissions that contribute to the progress of science

Modeling, simulation and experimental validation of polymer electrolyte membrane fuel cells and alkaline membrane fuel cells

Fuel cell technology is currently showing itself as a promising alternative for clean energy production due to its high efficiency and minimum environmental impact. However, its high cost is still a challenge that prevents this technology of being extensively used. A new conception and optimization are a natural alternative to reduce cost and make fuel cells increasingly more attractive for power generation. Geometric design, including the internal structure and external shape, considerably affect the thermal, fluid and electrochemical characteristics, which determines the polarization curves as well as the thermal and power inertia. In order to predict the response of fuel cells according to the variation of manufacturing materials, physical properties, operating and design parameters, a reliable simulation model (and computationally fast) is necessary. A simplified and comprehensive mathematical model for a polymer electrolyte membrane fuel cell (PEMFC) is developed and experimentally validated. Numerical results are obtained with the model for an existing set of ten commercial unit PEM fuel cells. The computed polarization and power curves are directly compared to the experimentally measured ones with good qualitative and quantitative agreement. Alkaline Membrane Fuel Cell (AMFC) is a recently developed fuel cell type, which has shown good experimental results. A mathematical model for a single AMFC with square section and fixed volume is introduced. The model is based on electrochemical principles, conservation of mass, momentum, energy and species. It also takes into account pressure drop in the gas channels and gradient of temperature with respect to space in the flow direction. The simulation results comprise temperature, net power, polarization curves and gas channels pressure drop. The computed temperature, polarization and power curves for AMFC are directly compared to the experimentally measured ones (using a prototype built in laboratory) with good qualitative and quantitative agreement. Therefore, the model is expected to be a useful tool for PEMFC and AMFC design and optimization

Modelagem matemática e simulaçao em tempo real de um trocador de calor regenerador

Orientador: José Viriato C. VargasCo-orientador: Juan Carlos OrdonezDissertaçao (mestrado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduaçao em Engenharia. Defesa: Curitiba, 2005Inclui bibliografiaÁrea de concentraçao: Engenharia de Processos Térmicos e Químico

P-15 Feasibility Study of Edificial Fuel Cell Applications at Andrews University

When evaluating energy systems, fuel cells have many favorable characteristics. A few of these characteristics include: next-to-zero pollutants, reliability, fuel flexibility, dual energy production (both electricity and heat), and high efficiencies when implementing Combined Heat and Power (CHP). Because of these advantageous characteristics, a study has been initiated to evaluate the feasibility of stationary fuel cell applications for facilities at Andrews University. The objective of this study is to, first, identify successful cases of fuel cells systems with CHP that have been implemented around the world. The second objective is to verify the economic viability of the installation of fuel cell systems for co-generation in stationary applications. The cost analysis will consider government incentive programs that subsidize environmentally beneficial projects