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O conhecimento das pressões parciais do etanol e da água, em função da composição da respectiva mistura binária líquida, para dada temperatura, permite efetuar a integração numérica da equação diferencial que rege a troca de componentes entre a fase gasosa e a líquida. Para isto é suposto que o ar na saída da mistura etanol e água corresponda ao equilíbrio. A equação diferencial utilizada é uma variante da clássica equação de Rayleigh para destilação simples. Partindo de dados tabelados para 25C, relativos às pressões de vapor parciais em misturas binárias Etanol e Água, a equação considerada é integrada, para uma ampla faixa de umidade relativa do ar de entrada e para uma faixa de concentrações iniciais/finais da fase líquida no intervalo de 1 a 99% em massa de etanol. Com base nos resultados obtidos, verifica-se que ocorre grande perda de massa na mistura etanol e água quando é usada uma solução alcoólica pouco hidratada (quase anidra), principalmente para baixos teores de umidade relativa presente no ar de entrada, no entanto para solução alcoólica muito hidratada a perda de massa é pequena, independente dos teores de umidade relativa.

The ability to produce potable water economically is the primary focus of seawater desalination research. There are numerous methods to desalinate water, including reverse osmosis, multi-stage flash distillation, and multi-effect evaporation. These methods cost more than potable water produced from natural resources; hence an attempt is made in this research project to produce potable water using a modified high-efficiency jet ejector in vapor-compression distillation. The greater efficiency of the jet ejector is achieved by properly mixing propelled and motive streams. From experiments conducted using air, the pressure rise across the jet ejector is better in case of one or two mixing vanes and the highest back pressure (pinch valve closed 83.33%). At other pinch valve closings, the air velocity through the jet ejector was high, so the extra surface area from the mixing vanes caused excessive friction and lowered the efficiency.

The ability to produce potable water economically is the primary focus of seawater desalination research. There are numerous methods to desalinate water, including reverse osmosis, multi-stage flash distillation, and multi-effect evaporation. These methods cost more than potable water produced from natural resources; hence an attempt is made in this research project to produce potable water using a modified high-efficiency jet ejector in vapor-compression distillation. The greater efficiency of the jet ejector is achieved by properly mixing propelled and motive streams. From experiments conducted using air, the pressure rise across the jet ejector is better in case of one or two mixing vanes and the highest back pressure (pinch valve closed 83.33%). At other pinch valve closings, the air velocity through the jet ejector was high, so the extra surface area from the mixing vanes caused excessive friction and lowered the efficiency.

The material and device characteristics of InGaN/GaN heterojunction bipolar transistors (HBTs) grown by metalorganic chemical vapor deposition are examined. Two structures grown on sapphire with different p-InxGa1-xN base-region compositions, xIn = 0.03 and 0.05, are presented in a comparative study. In a second experiment, NpN-GaN/InGaN/GaN HBTs are grown and fabricated on free-standing GaN (FS-GaN) and sapphire substrates to investigate the effect of dislocations on III-nitride HBT epitaxial structures. The performance characteristics of HBTs on FS-GaN with a 20×20 m2 emitter area exhibit a maximum collector-current density of ~12.3 kA/cm2, a D.C. current gain of ~90, and a maximum differential gain of ~120 without surface passivation. For the development of deep-ultraviolet optoelectronics, several various structures of optically-pumped lasers at 257, 246, and 243 nm are demonstrated on (0001) AlN substrates. The threshold-power density at room temperature was reduced to as low as 297 kW/cm2. The dominating polarization was measured to be transverse electric in all cases. InAlN material was developed to provide lattice matched, high-bandgap energy cladding layers for a III-N UV laser structure. This would alleviate strain and dislocation formation in the structure, and also mitigate the polarization charge. However, a gallium auto-doping mechanism was encountered which prevents the growth of pure ternary InAlN, resulting instead in quaternary InAlGaN. This phenomenon is quantitatively examined and its source is explored.

Submitted by Fellipe Sartori da Silva null (fellipe_sartori@yahoo.com) on 2018-03-20T14:29:37Z No. of bitstreams: 1 Determinação do custo de energia gerada através da utilização de células a combustível de carbonato fundido e turbina a vapor em um ciclo combinado.pdf: 3065864 bytes, checksum: 1b28d8ca48a059ab95292517f0d2d616 (MD5) / Approved for entry into archive by Pamella Benevides Gonçalves null (pamella@feg.unesp.br) on 2018-03-21T13:25:41Z (GMT) No. of bitstreams: 1 silva_fs_me_guara.pdf: 3065864 bytes, checksum: 1b28d8ca48a059ab95292517f0d2d616 (MD5) / Made available in DSpace on 2018-03-21T13:25:41Z (GMT). No. of bitstreams: 1 silva_fs_me_guara.pdf: 3065864 bytes, checksum: 1b28d8ca48a059ab95292517f0d2d616 (MD5) Previous issue date: 2018-02-07 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os modelos energéticos atuais são baseados majoritariamente na utilização de combustíveis fósseis, os quais, além de serem fontes finitas, ainda geram gases poluentes que contribuem para o efeito estufa e, consequentemente, para o aquecimento global. As células a combustível, por possuírem alta eficiência de conversão, baixa emissão, simplicidade de operação e flexibilidade em sua utilização, vêm sendo estudadas como opção mais limpa de geração. A célula a combustível de carbonato fundido, em particular, além de ter vantagens estruturais por operar a alta temperatura, possui calor residual que pode ser aproveitado para cogeração. O presente trabalho propõe uma configuração de ciclo combinado de uma célula a combustível de carbonato fundido de 10 MW, que possui reforma interna de gás natural, com um ciclo a vapor que aproveita o calor residual da célula. A reforma a vapor do gás natural, simulada pelo software STANJAN Chemical Equilibrium Solver, apresentou valores satisfatórios de produção de H2 na temperatura de operação da célula. As análises energética e exergética, simuladas através do software Engineering Equation Solver (EES), apontaram aumentos nas respectivas eficiências globais de 4,8 e 4,6%, respectivamente. A análise exergoeconômica indicou custo de geração de 0,4679 USD/kWh, valor acima das tarifas nacionais. Entretanto, a análise de sensibilidade mostrou que plantas de grande porte com essa configuração podem ser economicamente competitivas em diferentes cenários. / Current researches point to a significant increase in energy demand over the next few years. Energy models are mostly based on fossil fuels, which generates greenhouse gases that contribute to global warming. Thus, it becomes necessary to develop equipment and cycles that operate with greater efficiency, as well as new technologies of energy generation with both fossil and renewable sources. Fuel cells are being widely investigated due to their high conversion efficiency, low emissions, structural simplicity and flexibility. Among several fuel cell types, molten carbonate fuel cell has advantages such as fuel flexibility and high operating temperature, which leads to high thermal energy residue. This residue can be used for cogeneration and combined cycles, in order to enhance the global efficiency. This study aimed to introduce a 10 MW internal reforming molten carbonate fuel cell and steam turbine combined cycle. Steam reforming of natural gas was simulated by STANJAN Chemical Equilibrium Solver and presented satisfactory H2 production at MCFC operating temperature. Simulation in Engineering Equation Solver (EES) of energetic and exergetic analysis showed efficiency increases of 4,8 and 4,6%, respectively. Exergoeconomic analysis pointed to a 0,4679 USD/kWh power cost. However, sensitivity analysis showed that higher plants can achieve economic viability in different scenarios

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-01-26T19:01:21Z No. of bitstreams: 1 RegivaldoDeOliveiraFalcao_DISSERT.pdf: 2070708 bytes, checksum: d2030edd45895ed4d631e7484ff6f7c1 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-01-28T21:49:26Z (GMT) No. of bitstreams: 1 RegivaldoDeOliveiraFalcao_DISSERT.pdf: 2070708 bytes, checksum: d2030edd45895ed4d631e7484ff6f7c1 (MD5) / Made available in DSpace on 2016-01-28T21:49:26Z (GMT). No. of bitstreams: 1 RegivaldoDeOliveiraFalcao_DISSERT.pdf: 2070708 bytes, checksum: d2030edd45895ed4d631e7484ff6f7c1 (MD5) Previous issue date: 2014-12-19 / O presente trabalho teve como objeto de estudo um sistema de gera??o de vapor, distribui??o de vapor e retorno de condensado de uma planta t?xtil localizada no Rio Grande do Norte. O trabalho teve como base os seguintes objetivos: Conhecer o uso do vapor saturado de ?gua nos processos de tinturaria e acabamento em uma planta t?xtil; Estudar os diversos aspectos de um sistema de distribui??o de vapor, para identificar as formas em que ocorrem perdas de energia; Obter informa??es quantitativas das principais perdas de vapor no sistema de gera??o e distribui??o de vapor e mensurar as perdas, ?gua e vapor, do sistema; Utilizar o vapor flash como forma de redu??o de custo. Para isso fez-se uso da apura??o dos ganhos financeiros apresentados nas suas respectivas melhorias. Como base de dados para o desenvolvimento do trabalho utilizou-se registros de processos industriais, dados dos sistemas de utilidades, dados de an?lises de laborat?rio e de analisadores em linha, abrangendo o per?odo de 2013. Usando-se princ?pios consagrados das leis de conserva??o de massa e energia, o tratamento desses dados mostrou que as perdas de ?gua e energia no sistema de vapor s?o expressivas e que os ganhos ambientais e econ?micos que poder?o ser obtidos com a??es de melhoria s?o bastante significativas. Tomando como base os dados e resultados obtidos sugiro que os estudos futuros deem continuidade a abordagem sobre sistemas de gera??o de vapor, distribui??o e, principalmente, retorno de condensado / This study focused object a steam generation system, steam distribution and condensate return a textile plant located in Rio Grande do Norte. The work was based on the following objectives: Knowing the use of saturated water vapor in the dyeing and finishing processes in a textile plant; To study the various aspects of a steam distribution system to identify the ways in which energy losses occur; Obtain quantitative information of the main loss in steam generation system and steam distribution and to measure the losses, water and steam system; Using the flash steam as a means of cost reduction. For it was made use of the calculation of financial gains made in their respective improvements. As a database for the development of working registers are used in industrial processes, data from utility systems, laboratory data analysis and on-line analyzers, covering the period 2013. Using the principles set conservation laws mass and energy, those data showed that the loss of water and energy in the steam system are significant and that the environmental and economic gains to be obtained with improvement actions are quite significant. Based on the data and results suggest that future studies deem the continuity approach to steam generation systems, distribution and mainly condensate return.