Submitted by Raquel Vergara Gondran (raquelvergara38@yahoo.com.br) on 2016-04-10T18:48:47Z No. of bitstreams: 1 tesegilbertocorrafinal1.pdf: 1006084 bytes, checksum: 2219c9fe4c799231c3b10ed0f646d9d1 (MD5) / Approved for entry into archive by cleuza maria medina dos santos (cleuzamai@yahoo.com.br) on 2016-04-21T02:29:45Z (GMT) No. of bitstreams: 1 tesegilbertocorrafinal1.pdf: 1006084 bytes, checksum: 2219c9fe4c799231c3b10ed0f646d9d1 (MD5) / Made available in DSpace on 2016-04-21T02:29:45Z (GMT). No. of bitstreams: 1 tesegilbertocorrafinal1.pdf: 1006084 bytes, checksum: 2219c9fe4c799231c3b10ed0f646d9d1 (MD5) Previous issue date: 2009 / Neste trabalho foi analisado um sistema integrado de refrigeração compressãoabsorção, bem como foi feita uma simulação operacional no desempenho de um sistema utilizando os fluidos, amônia e água. Foram feitas comparações entre os coeficientes de desempenho do sistema e entre a relação de eficiência com a variação de parâmetros. Foi investigada a influência da efetividade do trocador intermediário na carga térmica dos componentes e no desempenho do sistema. Também foi realizada neste trabalho uma comparação entre o sistema de absorção e o de compressão mecânica. Os resultados obtidos permitiram escolher pela melhor condição de funcionamento deste sistema, em vista de um processo economicamente mais rentável. A simulação numérica é empregada para comparar o comportamento dos dois sistemas. Os resultados obtidos na comparação mostram que o sistema de refrigeração integrado, opera com uma redução de até 19,73% no COP. Entretanto, o sistema de refrigeração integrado apresentou um aumento de até 25,57%, em eficiência exergética e 33,09% em capacidade frigorífica em relação ao sistema convencional. Ainda neste trabalho foi proposto um modelo analítico para o cálculo do perfil de temperatura média em congelamento aplicada experimentalmente a castanha (Umbrina Sp.). O uso deste modelo analítico na determinação do perfil da temperatura média do alimento e a sua aplicação no cálculo da variação da taxa de calor removida mostraram-se muito eficiente, como ferramenta no suporte à decisão do uso, ou desenvolvimento de equipamentos na área da refrigeração, e no planejamento das linhas de produção. A curva de congelamento obtida no centro da amostra da castanha comparado com o modelo experimental indicou uma diferença de 6,37% a -18,2ºC (condição final experimental). diferente. / This work a system was analyzed a refrigeration system integrated compression-absorption as well as it was made an operational simulation in the acting of a system using the fluids, ammonia-water. They were made comparisons among the coefficients of acting of the system and among the efficiency relationship with the variation of parameters. The influence of the intermediate cooling effectiveness was investigated in the heat exchanged of the components and in the performance system. It is also presented in this work a comparison among the system absorption and compression. The obtained results allow choosing for the best condition of operation of this system, in view of a process more profitable economic. Still in this work an analytical model was proposed for the calculation of the profile medium temperature in freezing of foods and applied the argentine croaker experimentally (Umbrina Sp.). The use of this analytical model in the determination of the profile medium temperature of the food and his application in the calculation of the variation of the rate of heat transfer are shown very efficient, as decision support tools of the use, or development of equipments in the area of the cooling, and in the planning of the production lines.

Orientador: Roger Josef Zem / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-07-29T01:55:29Z (GMT). No. of bitstreams: 1 Maia_MariadeLourdesOliveira_D.pdf: 6396882 bytes, checksum: b0a06b7f265dff67b45f506f542329d9 (MD5) Previous issue date: 2001 / Resumo: Sistemas de destilação são amplamente utilizados em indústrias químicas e petroquímicas. Uma desvantagem desses sistemas, no entanto, é o fato dos mesmos apresentarem um grande consumo de energia. Dessa forma, a identificação de parâmetros como: refluxo mínimo, condição térmica da alimentação, posição do estágio da alimentação, etc., são extremamente importantes tanto para o projeto de colunas de destilação isoladas, como também para o seqüenciamento de colunas de destilação com reduzido consumo de energia. Visando a redução do consumo de energia de processos, a análise exergética tem sido amplamente utilizada. Por meio do cálculo do conteúdo de exergia das correntes do processo, é possível ter-se uma idéia da degradação da energia ao longo do mesmo. A medida da qualidade da energia é a exergia. O objetivo da análise exergética de processos é identificar as fontes de irreversibilidade, ou perda de exergia, e também identificar as modificações no processo que podem levar à redução dessa perda. Como resultado tem-se um menor consumo de energia. Somente recentemente, no entanto, a análise exergética tem sido aplicada a processos químicos. Como exemplo tem-se a metodologia proposta por Zemp (1994) na qual a seqüência ótima de colunas de destilação é a identificada como sendo a que apresenta menor perda de exergia. Uma desvantagem dessa metodologia, no entanto, é que a condição térmica da alimentação é fixada em líquido saturado. Neste trabalho, a análise exergética é utilizada na síntese e otimização de sistemas de destilação. Numa primeira etapa, o conceito de perfil quase-reversível para a separação de misturas multicomponentes em colunas de destilação isoladas foi utilizado, juntamente com a análise exergética, para a otimização da condição térmica da alimentação. Os bons resultados obtidos para vários sistemas motivaram a continuação do estudo em direção ao sequenciamento de colunas de destilação. O objetivo foi o de investigar se a otimização da condição térmica pode reduzir ainda mais o consumo de energia da seqüência previamente identificada como ótima. Modificação na pressão de operação das colunas da seqüência, assim como a influência da composição da alimentação, também foram consideradas. V ários sistemas com diferentes número de componentes foram utilizados para testar a metodologia. No caso dos sistemas temários, ambas as opções de seqüência foram estudadas. Os resultados provaram que a otimização das colunas não modifica a seqüência identificada como ótima. De uma maneira geral, foi possível propor uma metodologia para a síntese e otimização de sistema de destilação sem a necessidade da simulação rigorosa das colunas. Como vantagem tem-se o fato de que problemas de convergência não aparecem e não há a necessidade de se determinar o estágio da alimentação à priori / Abstract: Distillation systems are widely used in chemical and petrochemical industries. The main drawback of these systems, however, is the fact that they are energy intensive processes. Therefore, there is a need of a methodology that allows for the synthesis of distillation systems that present low energy consumption. In this sense, the correct identification of parameters such as: minimum reflux, feed stage location, etc plays an important role. In order to reduce the energy consumption of processes, the exergy analysis has appeared as an efficient too1. By computing the exergy content of the process streams the design engineer can understand how the energy degrades throughout the processo Exergy is a measurement of the quality of the energy. The goal of the exergy analysis is to identify sources of exergy losses, and the most appropriate modifications that will 1ead to the decrease of process irreversibility. As a result, the energy requirement of the process is reduced. Only recently, however, exergy analysis has been applied to chemical processo The optimum distillation column sequence, for example, was identified as the one that presents the lowest value of the minimum exergy loss (Zemp, 1994). However, the feed thermal condition is fixed as saturated liquido. In this work, exergy analysis is applied to the synthesis and optimisation of distillation columns sequences. Firstly, the concept of near-reversible column profile, together with the exergy analysis, were used to optimise the feed thermal condition of the feed. Secondly, it was investigated if different feed thermal condition can further reduce the overall energy consumption of a sequence. Not only were considered changes in the feed condition but it was also analysed other modifications in the operational conditions of each column of the sequence. The influence of the composition of the feed was tested as well. Several systems with different number of components were used to test the methodology. For the temary systems both direct and indirect separation were analysed. Results have shown that the optimisation of the columns do not change the selected optimum sequence. Overall, the exergy analysis applied to distillation systems has shown to be a useful tool to the synthesis and optimisation of such separation systems. By using the proposed methodology there is no need to resort to the rigorous simulation of each column of the sequence. Therefore, convergence problems as well as the tedious trial-and-error procedure for the determination of the optimal feed tray location are avoided. / Doutorado / Sistemas de Processos Quimicos e Informatica / Doutor em Engenharia Química

Orientador: Jose Vicente Hallak d'Angelo / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-15T03:30:00Z (GMT). No. of bitstreams: 1 Lobosco_RaquelJahara_M.pdf: 1406343 bytes, checksum: 34dc2d91be7e56471efaccf2dae92582 (MD5) Previous issue date: 2009 / Resumo: Este trabalho apresenta a proposta de uma função para avaliação do desempenho de ciclos de refrigeração, do ponto de vista termodinâmico e ambiental, através da análise estatística dos resultados da simulação computacional de um ciclo de refrigeração por compressão a vapor. A função proposta representa um índice global de avaliação da eficiência termodinâmica e dos critérios ambientais e foi desenvolvida com o intuito de facilitar a combinação de critérios utilizados na avaliação de ciclos termodinâmicos e envolve a análise exergética do ciclo, valores do COP (coefficient of performance), do ODP (ozone depletion potencial) e do GWP (Global Warming Potential). Para a simulação computacional foi utilizado o software Hysys versão 3.2 da Aspen Technology. As simulações permitiram testar diferentes combinações de misturas de refrigerantes. As equações de estado de Peng-Robinson e Peng-Robison Stryjek-Vera (PRSV) foram comparados entretanto a equação de estado Peng-Robinson foi utilizada neste trabalho para estimar as propriedades termodinâmicas. Foram consideradas neste trabalho duas eficiências do compressor, 55% e 75%. Nas simulações foram avaliados diversos refrigerantes puros (R134a, R290, R152a e R600a) e misturas binárias dos mesmos em três proporções mássicas: 75%, 50% e 25%. O desempenho do ciclo termodinâmico foi avaliado com uma variação de 10% e 20% das pressões da região de alta pressão e de baixa pressão e através dessa avaliação foi possível sugerir nova faixa de atuação das pressões visando uma otimização do ciclo. Através do índice da função de desempenho foi possível determinar que o R600a e suas misturas são os refrigerantes mais adequados para o ciclo proposto / Abstract: This work presents a proposal function to vapor compression refrigerator cycle performance from environmental and thermodynamic point of view. The function was developed through the statistic analysis of a refrigerator cycle computational results. The proposal function represents an evaluation indice of efficiency and environment criterions and was developed to make the analysis of combining criterions evaluations easier in thermodynamics cycles. It includes an exergetic analysis, COP (Coefficient of Performance), ODP (Ozone Depletion Potencial) and GWP (Global Warming Potential). Software Hysys version 3.2 from Aspen Technology was used for computational simulation development. The simulations allowed testing several combinations of refrigerants. The thermodynamic packages Peng-Robison and Peng-Robison Stryjek and Vera was compared however Peng-Robinson equation of state, was used to estimate thermodynamic properties of proposed cycle in this work. Two different efficiencies for the compressor were considered, 55% and 75%. The mixtures of refrigerants tested were pair's combinations of: R134a, R290, R152a and R600a. The variation of these mixtures was in the following proportions: 75, 50 e 25% and it was compared with the own refrigerant. In order to evaluate the performance of refrigerant mixtures, the pressure of high pressure region and low pressure region suffered a change of 10%. With this analysis was possible to suggest a new pressure range for cycle optimization. Considering the values of performance function, it was possible to conclude that R600a and its mixtures are the most indicated ones to be used in the proposed cycle / Mestrado / Sistemas de Processos Quimicos e Informatica / Mestre em Engenharia Química

Orientador: Jose Vicente Hallak D'Angelo / Teses (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-15T17:52:28Z (GMT). No. of bitstreams: 1 Fabrega_FrancinedeMendonca_D.pdf: 2288769 bytes, checksum: 42c859846af4183cbee87d9363d4cffb (MD5) Previous issue date: 2010 / Resumo: A indústria petroquímica é o setor industrial que utiliza como matéria prima derivados do petróleo, principalmente a nafta petroquímica, da qual se produzem substâncias como o etileno e propileno. Nesse processo industrial utilizam-se ciclos de refrigeração de larga escala que fornecem utilidades frias ao processo, em especial aos condensadores das colunas de destilação e destacam-se por serem grandes consumidores de energia, sendo de extrema importância que estes ciclos operem de forma otimizada visando a redução de custos. A Quattor Unidade de Químicos Básicos Cracker ABC, localizada no Pólo Petroquímico de Capuava, em Santo André (SP) vem produzindo atualmente 700 mil t/ano de etileno, sendo umas das principais produtoras do setor. A fim de reduzir os custos de processos industriais, as análises exergética e exergoeconômica seguidas da otimização termoeconômica são ferramentas que têm sido empregadas com sucesso. Neste trabalho, com o objetivo de otimizar o sistema de refrigeração que produz as utilidades frias, foi utilizado o simulador comercial Hysys© versão 3.2 para a simulação do processo produtivo e do ciclo de refrigeração, obtendo-se as grandezas termodinâmicas necessárias para o cálculo da análise exergética. Aplicando a metodologia desenvolvida por Lozano e Valero (1993) foi possível calcular os custos de cada corrente do processo utilizando o software Matlab 7.0. A otimização do processo foi realizada utilizando-se a ferramenta Optimizer presente no próprio simulador. A função objetivo foi definida visando minimizar a exergia destruída no processo e o método de otimização utilizado foi o SQP (Sequential Quadratic Programing). Com a metodologia aplicada a exergia destruída foi reduzida em 19,95%. Em relação aos custos exergéticos foi obtida uma redução de 10,94% e os custos exergoeconômicos foram reduzidos em 6,45% (SQP) representando uma economia de 77000 R$/h / Abstract: Petrochemical industries use many oil derivatives as raw materials, especially petrochemical naphtha, from which many chemicals, like ethylene and propylene, are obtained. The industrial process that produces these products uses large scale refrigeration cycles which generate the cold utilities streams used in the condensers of the distillation columns. These refrigeration cycles are great energy consumers, so it is very important that they operate in an optimized way in order to reduce operational costs. Quattor Unidade de Químicos Básicos Cracker ABC, located at Capuava Petrochemical Pole in Santo André (São Paulo State) produces 700 thousand tons of ethylene per year and is one of the main producers of the petrochemical sector in Brazil. Exergetic and exergoeconomic analysis followed by a procedure of thermoeconomic optimization are a set of important tools used to improve industrial processes and they have been used successfully in many cases. In this work, aiming the optimization of the refrigeration system that generates the cold utilities for the process, a commercial simulator, Hysys© version 3.2, was used to simulate both the industrial process of ethylene and propylene production and the refrigeration cycles of the process, obtaining the thermodynamic properties of the streams present in the process, which are necessary for the exergetic analysis. Using the methodology developed by Lozano and Valero (1993) it was possible to calculate the costs of each process stream using software Matlab 7.0. The optimization of the process was performed using the Optimizer Tool available in the simulator, by defining an objective function to be minimized as being the total destroyed exergy in the process. The chosen optimization method was SQP (Sequential Quadratic Programming). With these tools and using the referred methodology, the total destroyed exergy in the process was reduced in 19.95%. Considering exergetic costs, a reduction of 10.94% was achieved and the exergoeconomic costs were reduced in 6.45%, representing an economy of 77000 R$/h for the process / Doutorado / Sistemas de Processos Quimicos e Informatica / Doutor em Engenharia Química

Please read the abstract (Synopsis) in the section 00front of this document / Dissertation (M Eng (Chemical Engineering))--University of Pretoria, 2007. / Chemical Engineering / MEng / unrestricted

No description available.

The combination of the continuously growing demand of energy in the world, the depletion of oil and its sharp price increase, as well as the urgent need for cleaner and more efficient fuels have boosted the global trade of liquefied natural gas (LNG). Nowadays, there is an increasing interest on the design philosophy of the LNG receiving terminals, due to the fact that the existing technologies either use seawater as heating source or burn part of the fuel for regasifying LNG, thus destroying the cryogenic energy of LNG and causing air pollution or harm to marine life. This investigation addresses the task of developing novel systems able to simultaneously regasify LNG and generate electric power in the most efficient and environmentally friendly way.    Existing and proposed technologies for integrated LNG regasification and power generation were identified and simple, efficient, safe and compact alternatives were selected for further analysis. A baseline scenario for integrated LNG regasification and power generation was established and simulated, consisting of a cascaded Brayton configuration with a typical small gas turbine as topping cycle and a simple closed Brayton cycle as bottoming cycle. Various novel configurations were created, modeled and compared to the baseline scenario in terms of LNG regasification rate, efficiency and power output. The novel configurations include closed Rankine and Brayton cycles for the bottoming cycle, systems for power augmentation in the gas turbine and combinations of options. A study case with a simple and compact design was selected, preliminarily designed and analyzed according to characteristics and costs provided by suppliers. The performance, costs and design challenges of the study case were then compared to the baseline case. The results show that the study case causes lower investment costs and a smaller footprint of the plant, at the same time offering a simple design solution though with substantially lower efficiencies.

This report represents an overall view on thermodynamical studies of wastewater treatment plant, concepts like exergy, emergy and entropy. In addition, there has been an introduction of calorimetry. A common unit of measurement of organic contents in wastewater treatment facilities is COD. However, the unit of measurement which shows the sustainability of an industry is exergy and emergy. According to the calculations represented in this report it has been tried to make a correlation between the COD and exergy in order to make it easier to assess the sustainability of a treatment plant. The calorific measurement methods which have been used in the food science can also be used in wastewater treatment industry. Therefore, it is possible to replace COD and BOD measurement devices with online calorific measurements. It has been tried to find a correlation between exergy value and calorific contents. Accordingly, if the calorific values in wastewater input and output are known they can be transferred into exergy values. The energy and exergy production from wastewater has been observed in a Microbial Fuel Cell made in the laboratory and the measured values of current produced by the microbial activities has been analyzed in this report. For future studies, exergy can be used directly in modeling a wastewater treatment plant and improving an already made one.

A typical approach to the synthesis/design optimization of energy systems is to only use steady state operation and high efficiency (or low total life cycle cost) at full load as the basis for the synthesis/design. Transient operation as reflected by changes in power demand, shut-down, and start-up are left as secondary tasks to be solved by system and control engineers once the synthesis/design is fixed. However, transient regimes may happen quite often and the system response to them is a critical factor in determining the system's feasibility. Therefore, it is important to consider the system dynamics in the creative process of developing the system. A decomposition approach for dynamic optimization developed and applied to the synthesis/design and operation/control optimization of a solid oxide fuel cell (SOFC) based auxiliary power unit (APU) is the focus of this doctoral work. Called DILGO (Dynamic Iterative Local-Global Optimization), this approach allows for the decomposed optimization of the individual units (components, sub-systems or disciplines), while taking into account the intermediate products and feedbacks which couple all of the units which make up the overall system. The approach was developed to support and enhance current engineering synthesis/design practices by making possible dynamic modular concurrent system optimization. In addition, this approach produces improvements in the initial synthesis/design state at all stages of the process and allows any level of complexity in the unit's modeling. DILGO uses dynamic shadow price rates as a basis for measuring the interaction level between units. The dynamic shadow price rate is a representation of the unit's cost rate variation with respect to variations in the unit's coupling functions. The global convergence properties of DILGO are seen to be dependent on the mathematical behavior of the dynamic shadow price rate. The method converges to a "global" (system-level) optimum provided the dynamic shadow price rates are approximately constant or at least monotonic. This is likely to be the case in energy systems where the coupling functions, which represent intermediate products and feedbacks, tend to have a monotonic behavior with respect to the unit's local contribution to the system's overall objective function. Finally, DILGO is a physical decomposition used to solve system-level as well as unit-level optimization problems. The total system considered here is decomposed into three sub-systems as follows: stack sub-system (SS), fuel processing sub-system (FPS), and the work and air recovery sub-system (WRAS). Mixed discrete, continuous, and dynamic operational decision variables are considered. Detailed thermodynamic, kinetic, geometric, physical, and cost models for the dynamic system are formulated and implemented. All of the sub-systems are modeled using advanced state-of-the-art tools. DILGO is then applied to the dynamic synthesis/design and operation/control optimization of the SOFC based APU using the total life cycle cost as objective function. The entire problem has a total of 120 independent variables, some of which are integer valued and dynamic variables. The solution to the problem requires only 6 DILGO iterations. / Ph. D.

Thermal energy storage (TES) is an advanced technology for storing thermal energy that can mitigate environmental impacts and facilitate more efficient and clean energy systems. Thermochemical TES is an emerging method with the potential for high energy density storage. Where space is limited, therefore, thermochemical TES has the highest potential to achieve the required compact TES. Principles of thermochemical TES are presented and thermochemical TES is critically assessed and compared with other TES types. The integration of TES systems with heating, ventilating and air conditioning (HVAC) applications is examined and reviewed accounting for various factors, and recent advances are discussed. Thermodynamics assessments are presented for general closed and open thermochemical TES systems. Exergy and energy analyses are applied to assess and compare the efficiencies of the overall thermochemical TES cycle and its charging, storing and discharging processes. Examples using experimental data are presented to illustrate the analyses. Some important factors related to design concepts of thermochemical TES systems are considered and preliminary design conditions for them are investigated. Parametric studies are carried out for the thermochemical storage systems to investigate the effects of selected parameters on the efficiency and behavior of thermochemical storage systems. / UOIT