Obtenção de Propriedades Físico-Químicas de Misturas de Hidrocarbonetos em Baixa e Alta Pressão Visando a Caracterização e a Modelagem

The composition of petroleum may change from well to well and its resulting characteristics influence significantly the refine products. Therefore, it is important to characterize the oil in order to know its properties and send it adequately for processing. Since petroleum is a multicomponent mixture, the use of synthetic mixtures that are representative of oil fractions provides a better understand of the real mixture behavior. One way for characterization is usually obtained through correlation of physico-chemical properties of easy measurement, such as density, specific gravity, viscosity, and refractive index. In this work new measurements were obtained for density, specific gravity, viscosity, and refractive index of the following binary mixtures: n-heptane + hexadecane, cyclohexane + hexadecane, and benzene + hexadecane. These measurements were accomplished at low pressure and temperatures in the range 288.15 K to 310.95 K. These data were applied in the development of a new method of oil characterization. Furthermore, a series of measurements of density at high pressure and temperature of the binary mixture cyclohexane + n-hexadecane were performed. The ranges of pressure and temperature were 6.895 to 62.053 MPa and 318.15 to 413.15 K, respectively. Based on these experimental data of compressed liquid mixtures, a thermodynamic modeling was proposed using the Peng-Robinson equation of state (EOS). The EOS was modified with scaling of volume and a relatively reduced number of parameters were employed. The results were satisfactory demonstrating accuracy not only for density data, but also for isobaric thermal expansion and isothermal compressibility coefficients. This thesis aims to contribute in a scientific manner to the technological problem of refining heavy fractions of oil. This problem was treated in two steps, i.e., characterization and search of the processes that can produce streams with economical interest, such as solvent extraction at high pressure and temperature. In order to determine phase equilibrium data in these conditions, conceptual projects of two new experimental apparatus were developed. These devices consist of cells of variable volume together with a analytical static device. Therefore, this thesis contributed with the subject of characterization of hydrocarbons mixtures and with development of equilibrium cells operating at high pressure and temperature. These contributions are focused on the technological problem of refining heavy oil fractions

Sistema de secagem solar para frutos tropicais e modelagem da secagem de banana em um secador de coluna estática

In this study were projected, built and tested an electric solar dryer consisting of a solar collector, a drying chamber, an exhaust fan and a fan to promote forced hot air convection. Banana drying experiments were also carried out in a static column dryer to model the drying and to obtain parameters that can be used as a first approximation in the modeling of an electric solar dryer, depending on the similarity of the experimental conditions between the two drying systems. From the banana drying experiments conducted in the static column dryer, we obtained food weight data as a function of aqueous concentration and temperature. Simplified mathematical models of the banana drying were made, based on Fick s and Fourier s second equations, which were tested with the experimental data. We determined and/or modeled parameters such as banana moisture content, density, thin layer drying curves, equilibrium moisture content, molecular diffusivity of the water in banana DAB, external mass transfer coefficient kM, specific heat Cp, thermal conductivity k, latent heat of water evaporation in the food Lfood, time to heat food, and minimum energy and power required to heat the food and evaporate the water. When we considered the shrinkage of radius R of a banana, the calculated values of DAB and kM generally better represent the phenomenon of water diffusion in a solid. The latent heat of water evaporation in the food Lfood calculated by modeling is higher than the latent heat of pure water evaporation Lwater. The values calculated for DAB and KM that best represent the drying were obtained with the analytical model of the present paper. These values had good agreement with those assessed with a numeric model described in the literature, in which convective boundary condition and food shrinkage are considered. Using parameters such as Cp, DAB, k, kM and Lfood, one can elaborate the preliminary dryer project and calculate the economy using only solar energy rather than using solar energy along with electrical energy

Avaliação da eficiência térmica de um coletor solar tipo tubo evacuado modificado

Pós-graduação em Engenharia Mecânica - FEB

Modelagem de ciclos combinados integrados à incineração de resíduos sólidos municipais

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Desenvolvimento experimental e simulação numérica de uma réplica térmica de placa de circuito impresso

Pós-graduação em Engenharia Mecânica - FEIS

Modelagem e simulação numérica de um sistema de refrigeração por absorção utilizando o par H2O-LiBr

The term refrigeration solar refers to any air conditioning system that uses solar energy as a primary energy source. The use of solar radiation for cooling purposes is divided according to their technological possibilities which are distinguished from one another as the way that energy is involved in the cycle, work or heat. The first case is related to vapor compression cycles, in which the work input is provided by the photovoltaic conversion of solar energy into electrical energy. In the second case, an absorption refrigeration cycle is used and the thermal energy collected from the solar radiation is provided at the generator of this cycle.. In this work a system with an absorption cycle using the pair BrLi-water, using solar energy as input is modeled. It is considered a simple refrigeration cycle whose the equations of mass and energy conservation in each component are developed in order to obtain an algebraic equation set and a simulation routine using the EES software. Although the simulation operates under certain specified thermal load it is possible to estimate the necessary areas of heat exchangers and solar collectors

Modelagem e avaliação de um sistema de refrigeração por absorção para residências e instalações de pequeno porte

This work presents a study of the absorption refrigeration system and the modeling and evaluation of two cycles using the binary solutions water-lithium bromide and ammonia-water for an equipment to be used in small size plants like residences. The study and evaluation aims the complete understanding of all parts of the system and the influence of each one of them as well as the spread of the knowledge to raise the use of this type of equipment in all sizes in order to decrease the energetic consumption of plants of all scales and making viable the alternative sources. The study is done in each element of the cycle separately and in some auxiliary equipments required in the operation such as the main power source, the solar collector. The software used for modeling, with emphasis on thermal part, was the EES (Engineering Equation Solver), that permitted the thermal balance calculus and acquisition of the used fluids properties. The results obtained for the equipment shows the system is more complex than the widely used in business, however, it can be viable and represents an alternative to increase the energetic efficiency

Equações de taxa aplicadas na modelagem de dispositivos fotodetectores baseados em poços quânticos

In this work, it is presented a novel method for calculating some intrinsic parameters such as capture mean time, thermic emission mean time, capture probability and noise gain on quantum well infrared photodetectors. Such devices are built by depositing layers of semiconductors of different energy gap, forming quantum wells. The present method uses rate equations to describe the occupation of discrete states of the quantum wells, that together with noise gain equations given in literature, are solved self consistently. The input data of the method is experimental measurement of dark current (current measured with no relevant incident photon) versus applied bias. In order to validate this approach, the values obtained were compared with results from literature

Modelagem de motor de combustão internae simulação do processo de queima de combustível

The internal combustion engine is a heat engine widely used in the automotive industry. In order to better understand its behavior many models in the literature have been proposed in the last years. The 0-D thermodynamic model is a fairly simple tool but it is very useful to understand the phenomenon of combustion inside the chamber of internal combustion engines. In the first phase of this work, an extensive literature review was made in order to get information about this kind of analysis and, after this, apply them in a model able to calculate the instantaneous temperature and pressure in one zone of the combustion chamber of a diesel engine. Therefore some considerations were made with the aim of increasing the accuracy of the model in predicting the correct behavior of the engine, adding the combined effects of heat transfer, leakage and injection. In the second phase, the goal was to study the internal flow of a three-dimensional model of an internal combustion engine. In order to achieve this goal the software Solidworks was used to create the geometries of an engine and the suite of softwares Ansys was used to create the moving mesh (ICEM CFD and CFX-Pre) and to solve the CFD problem (Ansys CFX code). The model was able to perform the air flow simulation during the four-stroke cycle of an engine: admission, compression, expansion and exhaust. The results obtained from both models were suitable and they open a new range of possibilities for future researches on the field

Modelagem e simulação de ciclos a gás com resfriamento de ar na entrada

The optimization of energy generation systems has become a key issue for technological and social development, mainly in developing countries, where the electricity consumption rises sharply. Gas turbine cycle is an electricity generating system, which studies have demonstrated that inlet air cooling increases net power and thermal efficiency. Thus, this study intends to quantify these parameters for environments with different ambient temperature and relative humidity. Two types of air cooling were used: evaporative and absorption systems. The configuration parameters only with the gas turbine cycle were compared to those whose configuration allowed cooling. First, it was analyzed only evaporative cooling. Next, the absorption system was used for analysis. The last configuration mixed these two methods, dividing equally its flow. The results showed that thermal efficiency and net power increase in any case of cooling, with absorption system more advantageous in terms of generated energy, where an increase between 1 and 2 MW was observed, depending on the ambient conditions . When the two methods were working together at low relative humidity, it showed a thermal efficiency increase compared to absorption system, up to 2.4%. Evaporative cooling was less effective, but it is a good and cheap possibility to increase the cycle parameters at high temperature and low relative humidity

Modelagem e simulação de ciclos a gás com resfriamento de ar na entrada

The optimization of energy generation systems has become a key issue for technological and social development, mainly in developing countries, where the electricity consumption rises sharply. Gas turbine cycle is an electricity generating system, which studies have demonstrated that inlet air cooling increases net power and thermal efficiency. Thus, this study intends to quantify these parameters for environments with different ambient temperature and relative humidity. Two types of air cooling were used: evaporative and absorption systems. The configuration parameters only with the gas turbine cycle were compared to those whose configuration allowed cooling. First, it was analyzed only evaporative cooling. Next, the absorption system was used for analysis. The last configuration mixed these two methods, dividing equally its flow. The results showed that thermal efficiency and net power increase in any case of cooling, with absorption system more advantageous in terms of generated energy, where an increase between 1 and 2 MW was observed, depending on the ambient conditions . When the two methods were working together at low relative humidity, it showed a thermal efficiency increase compared to absorption system, up to 2.4%. Evaporative cooling was less effective, but it is a good and cheap possibility to increase the cycle parameters at high temperature and low relative humidity

Secagem de resíduo de goiaba em secador convectivo de bandejas: modelagem matemática e análise do processo

Actually, Brazil is one of the larger fruit producer worldwide, with most of its production being consumed in nature way or either as juice or pulp. It is important to highlig ht in the fruit productive chain there are a lot lose due mainly to climate reasons, as well as storage, transportation, season, market, etc. It is known that in the pulp and fruit processing industy a yield of 50% (in mass) is usually obtained, with the other part discarded as waste. However, since most this waste has a high nutrient content it can be used to generate added - value products. In this case, drying plays an important role as an alternative process in order to improve these wastes generated by the fruit industry. However, despite the advantage of using this technique in order to improve such wastes, issues as a higher power demand as well as the thermal efficiency limitation should be addressed. Therefore, the control of the main variables in t his drying process is quite important in order to obtain operational conditions to produce a final product with the target specification as well as with a lower power cost. M athematical models can be applied to this process as a tool in order to optimize t he best conditions. The main aim of this work was to evaluate the drying behaviour of a guava industrial pulp waste using a batch system with a convective - tray dryer both experimentally and using mathematical modeling. In the experimental study , the dryin g carried out using a group of trays as well as the power consume were assayed as response to the effects of operational conditions (temperature, drying air flow rate and solid mass). Obtained results allowed observing the most significant variables in the process. On the other hand, the phenomenological mathematical model was validated and allowed to follow the moisture profile as well as the temperature in the solid and gas phases in every tray. Simulation results showed the most favorable procedure to o btain the minimum processing time as well as the lower power demand.

Modelagem e análise de um dispositivo mitigador de flecha para linhas de transmissão de energia elétrica baseado em ligas com memória de forma

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Mecânica, 2016.

Modelagem da informação para arquitetura da informação : diretrizes para elaboração de metodologia para a Câmara dos Deputados

Analisa elementos da arquitetura da informação, princípios de organização da informação, organização do conhecimento e gestão da informação, bem como estabelece diretrizes para a elaboração de uma metodologia para modelagem da informação na Câmara dos Deputados, produto previsto no projeto de Arquitetura de Informação em andamento na instituição.

Avaliação de Processo : Modelagem do processo de elaboração do Relatório de Auditoria de Gestão

Analisa o projeto de modelagem dos processos da Secretaria de Controle Interno – Secin, integrante do planejamento estratégico para o período 2014 – 2015. A abordagem do estudo é descritiva, sendo esperados como resultado o fortalecimento da estrutura de controles internos da secretaria e o aperfeiçoamento do processo de auditar a gestão anual da Câmara dos Deputados.