This thesis is focused in calculation and designing of fluid bed boiler for burning coal and wood biomass in the form of wood chips. The uniqueness of fluidized bed boiler is circulating fluidized layer and cyclone ash separator from flue gases beyond the combustion chamber.Work was divided into several parts due to different parameters of the fuel.. Stoichiometry calculations, emissions calculations, enthalpy of combustion and flue gas desulphurization calculations are performed in various parts.Further, calculating of the losses of boiler and its efficiency comparing to the calculation and design of each heat transfer surfaces was also solved so that resulting size and quantity meet the required specifications.Drawn set of this designed boiler based on calculations is included in the annex to this paper.

This thesis is focused in calculation and designing of fluid bed boiler for burning coal and wood biomass in the form of wood chips. The uniqueness of fluidized bed boiler is circulating fluidized layer and cyclone ash separator from flue gases beyond the combustion chamber.Work was divided into several parts due to different parameters of the fuel.. Stoichiometry calculations, emissions calculations, enthalpy of combustion and flue gas desulphurization calculations are performed in various parts.Further, calculating of the losses of boiler and its efficiency comparing to the calculation and design of each heat transfer surfaces was also solved so that resulting size and quantity meet the required specifications.Drawn set of this designed boiler based on calculations is included in the annex to this paper.

The Ground Source Heat Pump systems (GSHP) are an emerging technology used to exchange heat with the ground through the use of some buried heat exchangers. The thermal response of a borehole field can be characterized by its g-function. It is a non-dimensional temperature response factor, which can be calculated using either numerical or analytical solutions. Eskilson developed the first study made for the calculation of these g-functionts. Lamarche and Beauchamp proposed another analytical approach based on the Finite Line Source (FLS). Generally, both solutions present similar results with some small differences. They could be attributed to the boundary condition performed in both researches: the FLS solution considers uniform heat flux along the borehole wall in all the heat exchangers, while Eskilson’s model defines as a condition, uniform temperature at the borehole wall within all the pipes in the field. In this Master of Science Thesis, the temperature response factors (g-functions) of a 6x6 borehole field with 36 heat exchangers (BHE) arranged in a squared configuration are obtained from new numerical models, mainly based on the use of a highly conductive material composing the BHE. For this purpose, a commercial software called Comsol Multyphisics© is employed. The aim of this thesis is to get larger knowledge in generating the g-function in relation to the boundary condition performed in the model trying to reach better approximations to the reality. Some strategies with respect to the geometry, size of the model and mesh are performed to reduce the computing time. The influence of the geothermal heat flux and the influence of the highly conductive material (HCM) composing the BHEs are also studied in our model. Going further, the thermal behavior of the ground is also studied by imposing variable heating and cooling loads during seasonal periods over a time of 25 years. Finally, the g-functions obtained from our numerical models are compared to the one generated with the commercial software, Earth Energy Design (EED), which represents the numerical solution proposed by Eskilson, and the one generated with FLS approach. The results may explain in a closer approximation to the reality the thermal response for large borehole fields.

No description available.

Call number: LD2668 .T4 1985 S335 / Master of Science

Les échangeurs de chaleur sont des dispositifs largement utilisés dans divers systèmes énergétiques. Les présents travaux de recherche s’intéressent à la conception des échangeurs bi-fluides monophasiques par des méthodes d’optimisation topologique. A la différence des méthodes conventionnelles d’optimisation de taille et de forme, ces méthodes permettent une liberté de conception plus grande et ne nécessitent aucune définition a priori de la géométrie de l’échangeur. L’optimisation topologique bi-fluide consiste donc à réorganiser librement deux fluides et un solide dans un domaine d’optimisation. Les deux fluides doivent connecter les zones d’entrée aux zones de sortie en évitant tout mélange entre fluides. Dans le cadre de cette thèse, la méthode SIMP « Solid Isotropic Material with Penalization » a été utilisée. Divers algorithmes constituant cette méthode ont été formulés et testés : la méthode des volumes finis a été choisie pour la résolution du problème direct, la méthode des adjoints discrets pour le calcul du gradient de la fonction objectif et enfin la méthode des asymptotes mobiles pour guider l’optimisation numérique. Les résultats des simulations ont permis de définir différentes formes d’échangeurs de chaleur en 2D. On a fait varier le nombre d’entrées et de sorties ainsi que les débits de chaque fluide. Les travaux montrent la capacité de cette méthode à concevoir des formes innovantes d’échangeur de chaleur. La thèse établit ainsi les bases d’une nouvelle méthode de conception des échangeurs de chaleur. / Heat exchangers are devices widely used in various energy systems. The present research work focuses on the design of single-phase bi-fluid heat exchangers by using topology optimization methods. Unlike conventional size and shape optimization methods, topology optimization methods allow greater design freedom and do not require prior definition of the exchanger geometry. Hence, bi-fluid topology optimization consists of freely reorganizing two fluids and one solid in the optimization domain. Both fluids should connect inlet sections to outlet sections while avoiding any fluid mixture inside the domain. SIMP method “Solid Isotropic Material with Penalization” is used within the framework of this thesis. This method includes various algorithms that were formulated and tested : finite volume method was selected for solving the direct physical problem, discrete adjoint method was used for the calculation of the gradient of the objective function, and the method of moving asymptotes was adopted to guide the numerical optimization. Simulation results have allowed the definition of various heat exchanger shapes in 2D. The number of inlet and outlet as well as the flow rates of each fluid have been varied. The works have shown the ability of this method to design innovative shapes of heat exchangers. Hence, the thesis establishes the basis of a new design methodology of heat exchangers.

[pt] Um gerador de pasta de gelo foi desenvolvido para o estudo experimental de suas características de transferência de calor. Uma das características da pasta de gelo é que pode ser bombeada como qualquer líquido. O gerador de pasta de gelo é um evaporador, do tipo trocador de calor de superfície raspada com intensificação mecânica de transferência de calor. Foi estabelecida a influência de vários parâmetros na transferência de calor no gerador de pasta de gelo: a vazão mássica, a velocidade de rotação do raspador, a temperatura da parede na interface, a temperatura de operação da solução aquosa, entre outros. Estudou-se tanto a transferência de calor com ou sem mudança de fase. Utilizaram-se soluções aquosas de etanol com diferentes concentrações. A pasta de gelo era produzida continuamente sem acumulação no evaporador. O gerador era parte de um sistema integral contendo os seguintes componentes: o sistema de medição da fração de gelo on-line, através da medição da massa específica da pasta de gelo; uma bomba helicoidal de cavidade progressiva, que permitia controlar a vazão, por meio de um variador de freqüência; um aquecedor elétrico, atuando como carga térmica, com a possibilidade de variar a capacidade desta carga térmica e, com isto, o controle da temperatura de operação do sistema; e o sistema de aquisição de dados. Foi estabelecido um modelo para determinar, experimentalmente, o número de Nusselt e, por conseguinte, o coeficiente interno de transferência de calor da pasta de gelo. Utilizou-se uma unidade condensadora convencional, com R22 como fluido refrigerante. A pasta de gelo resultante era bombeada continuamente em um circuito fechado, assegurando o estudo de um fluido homogeneamente distribuído, visto que o circuito não permitia a acumulação de pasta de gelo. Os sistemas de geração de pasta de gelo apresentam potencial para reduzir significativamente os custos de capital inicial e operação, quando comparados com tecnologias de sistemas de termoacumulação estáticos de gelo ou dinâmicos, como o ice harvesting. / [en] An ice slurry generator for was developed for the experimental study of its heat transfer characteristics. One of the main characteristic of ice slurry is that it can be pumped as any liquid. The ice slurry generator is an evaporator, with mechanical heat transfer enhancement, by surface scraping. The dependence of several parameters on heat exchanger performance was established. They included: mass flow rate, scraped rotational velocity, surface temperature, solution operating temperature. Single and two-phase flow was studied. Aqueous ethanol solutions, of different concentrations, were used. Ice slurry was produced on a continuous basis. The experimental apparatus consisted of the heat exchanger itself, an on-line ice mass fraction measurement device, a helicoidal positive displacement variable flow rate pump, an electrical heater, the data acquisition system and a R22 condensing unit. The ice slurry was pumped continuously on a closed circuit, providing a homogeneous fluid, as no accumulation of ice was possible. Ice slurry systems have the potential of significant reduction on capital and maintenance costs, when compared to traditional technologies, static or dynamic, of ice thermoaccumulation.

Este trabalho visa o estudo de uma metodologia de simulação numérica aplicada ao processo de troca térmica do motor de um veículo de passeio. O processo de troca térmica é essencial para evitar o superaquecimento do motor, que provoca o rompimento do filme de óleo lubrificante dos pistões e, conseqüentemente, o seu travamento. Essa metodologia será útil nos estudos preliminares do sistema de arrefecimento de um veículo na fase inicial de projeto por meio de simulações virtuais, o que possibilitará a redução de protótipos, além de proporcionar um ganho em tempo de resposta. A metodologia utiliza um programa comercial de CFD para a simulação do processo de troca térmica no interior do compartimento do motor do veículo. As simulações foram realizadas com base nos testes físicos em túnel de vento que fazem parte do desenvolvimento e projeto de automóveis em condições de operação que representam situações críticas integrantes da vida operacional. Essas condições operacionais de teste, tais como a velocidade do veículo, as cargas térmicas, a potência dos ventiladores e outros parâmetros foram utilizadas como condições de contorno na validação do modelo do veículo. O processo de validação de modelos é composto por: validações de itens isolados do sistema de arrefecimento, avaliação do efeito da densidade de malha computacional de um modelo completo na vazão de ar nos trocadores de calor e simplificações no modelo para a redução do tempo de processamento. Neste trabalho três modelos distintos de veículos foram utilizados, sendo que dois deles para a validação na comparação com os resultados de túnel vento, enquanto o terceiro modelo foi utilizado para a validação da metodologia através de comparações com os dados obtidos nos testes em pista circular. Os resultados das simulações mostraram variações máximas de 5,5% na temperatura do líquido de arrefecimento na entrada do radiador em relação aos testes. A metodologia de simulação mostrou ser uma poderosa ferramenta de otimização durante a fase de desenvolvimento do projeto e complementando os testes físicos para o sistema de arrefecimento veicular. / The present work is applied to a development of a numerical simulation methodology for a passenger vehicle engine cooling process. The heat exchange process is essential to avoid the engine overheat which may result in the piston oil film separation and consequently its halt. This methodology will be useful for the preliminary studies of the cooling system at the initial phase through the virtual simulations which can reduce the number of prototypes and save proposals\' time response. The methodology uses commercial CFD software for airflow simulation and the thermal process at under hood. The simulations were based on the physical wind tunnel tests that are part of the automotive development, with operational conditions representing critical situations experienced by a vehicle in its operating life. The test conditions, such as vehicle speed, thermal loads, fan power and other parameters were used as the boundary conditions for the model validation. The validation process is based on the following phases: validation of the isolated cooling system components, the effect of mesh density at cooling airflow using a complete vehicle model and model simplification in order to improve the processing time. In this work development, three different models were used; two of them for validation with test tunnel data and the third, was used for methodology validation through the circular road test. The simulation results for tunnel and circular road showed 5.5% of differences for the radiator coolant inlet temperature when compared with physical tests. The methodology of the simulation is a powerful tool for optimization during the development phase and complementing the physical tests for the vehicle cooling systems.

O etanol (álcool etílico) tem sido cada vez mais estudado e testado como combustível alternativo para substituição do uso de alguns derivados de petróleo em motores de combustão interna. O presente trabalho procura abordar o emprego do etanol na forma vaporizada em motores do ciclo Otto, objetivando a obtenção de melhores níveis de rendimento térmico total. Deste modo, um motor para teste de octanagem (motor CFR) foi equipado com um vaporizador de álcool instalado no coletor de escapamento, e após uma série de ensaios, várias análises puderam ser feitas. Essas considerações procuraram se ater a aspectos como rendimento térmico, relação ar/combustível, ângulo de avanço da centelha, temperatura de escape, assim como potência e eficiência volumétrica, levando em conta, sempre, a sua influência no funcionamento geral do motor. Ficou constatado que o motor movido a etanol vaporizado apresenta rendimento consideravelmente maior, menor consumo de combustível e funcionamento mais suave que aqueles verificados quando o mesmo motor e alimentado com álcool líquido. / The ethanol (ethyl alcohol) has been studied more and more as alternative fuel to replace some petroleum derivatives for internal combustion engines. The attached study examines the application of vaporized ethanol for Otto cycle engines, searching for better levels of total thermal efficiency. Therefore, an engine for test of octane number (CFR motor) was equipped with an alcohol vaporizer installed inside the escape pipe, and after many experiences, several analysis were made. The various analysis included aspects as thermal efficiency, air/fuel ratio, advance ignition, escape temperature, power and volumetric efficiency, always considering their influence on the operation of the engine. It was confirmed that the engine moved by vaporized ethanol presents higher thermal efficiency, smaller fuel consumption and smoother working than in case of alimentation by liquid alcohol.

O álcool etílico ou etanol vem se tornando, neste novo século, uma importante referência para estudos e aplicações que procuram um combustível alternativo ao uso de derivados de petróleo em motores de combustão interna. Neste trabalho, o uso do etanol vaporizado pelos gases de escape em motores do ciclo Otto busca a obtenção de melhores níveis de rendimento térmico e emissões de poluentes. Assim sendo, um motor de 1.0 litro foi montado em laboratório com um trocador de calor instalado ao lado do coletor de escapamento, e uma série de testes foram feitos, possibilitando uma cuidadosa análise quanto a rendimento térmico, relação ar/álcool, ângulo de avanço da centelha, temperatura de escape e gases de emissão, entre outros aspectos. Conclui-se que o motor a álcool vaporizado, em certos regimes de funcionamento, apresenta rendimento maior e emissões menores que aqueles verificados no motor a álcool líquido. / The ethyl alcohol or ethanol is becoming, in this new century, an important reference for studies and applications that search for an alternative fuel to be used in internal combustion engines, replacing oil derivatives. In this study, an Otto cycle engine is fueled with ethanol vaporized by the exhaust gases, aiming for better levels of thermal efficiency and exhaust emissions. Therefore, a 1.0 liter engine with a heat exchanger connected to the exhaust manifold was prepared in a test bench, and several tests were made, which allowed a criterious analysis about air/alcohol ratio, spark ignition time, exhaust temperature and exhaust emissions, and others. It was concluded that the engine fueled with vaporized alcohol presents, in some operation points, higher thermal efficiency and less emissions compared to the case of engine fueled with liquid alcohol.