PPG Engenharia Mecânica
http://repositorio.jesuita.org.br/handle/UNISINOS/1690
PPG Engenharia MecânicaWed, 17 Jul 2024 22:00:35 GMT2024-07-17T22:00:35ZComparação de diferentes tecnologias de baterias para sistemas solares fotovoltaicos conectados à rede
http://repositorio.jesuita.org.br/handle/UNISINOS/12940
Comparação de diferentes tecnologias de baterias para sistemas solares fotovoltaicos conectados à rede
Cisco, Lenon Audibert
Grid-connected photovoltaic solar power generation is a reality in Brazil, and its growing
expansion presents both advantages and challenges for the electricity grid. In order to
minimize the effects of climate dependence and generation peaks during sunny hours, the use of energy storage systems is a solution. However, the implementation and use of batteries also represents an increase in system costs and associated environmental impacts. In this work, three battery technologies were compared via the Vikor multi-objective decision method: Lithium-Ion, Lead-Acid and Nickel-Cadmium, with the aim of obtaining a recommendation for the system that best suits the parameters: carbon emissions and energy costs, technical performance, battery life and economic aspects. The decision algorithm is applied to situations where each parameter has the same weight, and to alternative scenarios where the decision has an environmental, economic, or electrical performance bias. To assess environmental aspects, cradle-to-grave life cycle assessment data is used, and the system is sized for a standard low-consumption home. This study found that the lithium-ion battery had the best performance among the aspects evaluated, with the lead-acid battery being intermediate and the nickel-cadmium battery being the technology furthest from the ideal solution. In alternative scenarios where decision-making favors environmental and electrical aspects, the lithium-ion battery is still recommended by the method. In a scenario where cost is prioritized, nickel-cadmium batteries were recommended.
Tue, 26 Sep 2023 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/129402023-09-26T00:00:00ZAnálise hemodinâmica computacional de artérias coronárias idealizadas com stents cilíndricos e cônicos
http://repositorio.jesuita.org.br/handle/UNISINOS/12939
Análise hemodinâmica computacional de artérias coronárias idealizadas com stents cilíndricos e cônicos
Telöken, Kristian Nascimento
In Brazil, most hospital admissions for the treatment of cardiovascular diseases involve coronary angioplasty procedures with the use of stents. However, a significant challenge is in-stent restenosis, which involves the accumulation of cells, requiring additional interventions. Despite efforts to improve the geometry and material of stents, a recent approach proposes the transition from cylindrical to conical stent geometry, aiming for better adaptation to the physiology of blood vessels. This study compares cylindrical and conical stents using Fluid-Structure Interaction (FSI) modelling and Computational Fluid Dynamics (CFD). Additionally, it explores the impact of different strut thicknesses (0.1 to 0.3 mm) in 12 simulations, 6 CFD, and 6 FSI, in models of cylindrical and conical arteries. Finite volume and finite element methods were employed to approximate the fluid and solid domains, respectively. Blood was modelled as non-Newtonian fluid using the Carreau model, with Womersley number ranging from 2.23 to 3.78 and Reynolds number from 251 to 381. A different velocity pulse was used for each artery type, with the same flow pulse. The solid domain was represented by the arterial wall and the stent, with their properties obtained through Granta Edupack software. Results highlight the importance of FSI analysis, revealing significant differences compared to CFD in terms of Oscillatory Shear Index (OSI), pressure differences, and Temporal Average Wall Shear Stress (TAWSS), where FSI modelling showed substantial differences over CFD modelling, confirming the significant importance of this analysis method. A greater difference was also achieved between different stent thicknesses, with three times lower stresses for the larger thickness compared to the smaller one. The FSI approach also provided promising
results with stresses reaching approximately 25% of the material yield stress of the
stent, indicating substantial potential for optimizing coronary stenosis treatment.
Thu, 04 Jan 2024 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/129392024-01-04T00:00:00ZEstudo numérico de um dispositivo de coluna de água oscilante para aproveitamento da energia das ondas do mar
http://repositorio.jesuita.org.br/handle/UNISINOS/12938
Estudo numérico de um dispositivo de coluna de água oscilante para aproveitamento da energia das ondas do mar
Thums, Esmael
Energy conversion devices from waves harness the kinetic energy of seawater movement and convert it into electrical energy. Oscillating water column (OWC) devices use the motion of the sea surface to compress the air in a hydro-pneumatic chamber connected to
a duct containing a turbine, which, in turn, drives a generator. Considering that existing wave energy converters have low efficiency, the literature suggests that there is room for
improvement in this type of device. The Constructal Design Method (CDM) has been used to search for designs that can maximize the available energy. Through numerical modeling and the use of computational fluid dynamics (CFD), researchers have studied how the geometry of converters affects their performance and how it can be optimized. In this study, CDM is employed with the assistance of Design of Experiments (DoE) techniques and optimization to obtain the optimal design for a two-chamber OWC device based on the results of CFD simulations. The considered system is a full-scale device subjected to waves with a length of 65.4 m, a period of 7.5 s, and a height of 1 m. The volume ratios between the two chambers and the aspect ratios of each chamber (V1/V2, H1/L1, and H2/L2) are the three degrees of freedom used for optimizing the performance indicator, which is the power extracted per wave cycle. By generating a response surface, it was possible to observe that the bestperforming device had V1/V2 = 1.2, H1/L1 = 0.34, and H2/L2 = 0.1, resulting in a mass flow rate of 34.41 kg/s, a pressure of 2643.031 Pa, and a hydropneumatic power of 8875.15 W.
Fri, 27 Oct 2023 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/129382023-10-27T00:00:00ZProdução de biocarvão a partir de biomassa de babaçu visando a aplicação agrícola
http://repositorio.jesuita.org.br/handle/UNISINOS/12639
Produção de biocarvão a partir de biomassa de babaçu visando a aplicação agrícola
Schvade, Débora Cristine
The babassu production chain is one of the most representative of vegetal extractivism in Brazil, but results in high generation of waste with potential for utilization. The present study aims to produce biochar from babassu biomass through pyrolysis process aiming at agricultural application. The precursor material was composed of babassu epicarp, mesocarp and endocarp and was characterized in clean and raw form. The production of biochar was carried out with the raw biomass in four operating conditions, and the obtained biochars were submitted to prior characterization tests. The production of biochar on a larger scale was carried out in a fixed bed reactor at a temperature of 350ºC, rate of 10ºC/min, residence time of 20 minutes and N2 flow of 1mL/min. The agricultural application consisted in subjecting L. sativa seeds to two treatments containing biochar (Bio25% and Bio50%), these treatments were compared to a control treatment (Bio0%), whose growth was evaluated for 28 days. The characterization of the biomasses resulted in 0.98 wt% of particles adhered to the biomass, higher fraction of particles with an average diameter of 3.57 mm for both biomasses, moisture content of 16.66 and 17.43 wt%, ash content of 1.76 and 2.04 wt%, volatile matter of 82.27 and 82.48 wt%, fixed carbon of 15.65 and 16.38 wt%, pH of 6.29 and 6.47, electrical conductivity of 445.0µS/cm and 436.6µS/cm, real specific mass of 1.3950 g/cm3 and 1.3989 g/cm3, surface area of
0.3422 m2/g and 0.5431 m2/g and higher calorific value of 18.326 MJ/kg and 18.674 MJ/kg for the clean and raw biomass, respectively. The elements K, Si, Ca, Fe, S, P,
Cu were identified in the biomasses, besides the element Al for the crude biomass. The babassu biochar produced on a larger scale showed yield of 33.26 wt%, higher particle fraction of 3.57mm, 4.71 wt% ash, 29.20 wt% volatile matter, 66.09 wt% fixed carbon, pH of 8.98, electrical conductivity of 138.1µS/cm, real specific mass of 1.3804 g/cm3, higher calorific value of 27.94 MJ/kg, elements K, Si, Ca, Fe, Mg, S, P, Cu and Rb and CEC of 34.77mmol/kg. In agricultural application it was observed that the treatments with biochar resulted in seedlings with greater height and more vivid coloration, indicating that babassu biochar may have potential to be used to improve soil characteristics for agricultural application.
Mon, 17 Apr 2023 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/126392023-04-17T00:00:00ZMetodologia de diagnóstico energético em sistemas de bombeamento de água do setor de saneamento pela análise de indicadores de desempenho
http://repositorio.jesuita.org.br/handle/UNISINOS/12506
Metodologia de diagnóstico energético em sistemas de bombeamento de água do setor de saneamento pela análise de indicadores de desempenho
Lindau, Marcos Gaudie Ley
Wed, 22 Mar 2023 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/125062023-03-22T00:00:00ZDesign construtal para alto desempenho em arranjos de tubos e micromisturadores via simulação numérica
http://repositorio.jesuita.org.br/handle/UNISINOS/12505
Design construtal para alto desempenho em arranjos de tubos e micromisturadores via simulação numérica
Cunegatto, Eduardo Henrique Taube
The combination of the Response Surface Method (RSM) and Constructional Design Method (CDM) was applied in the investigation of two problems: configurations of tube arrangements for heat transfer in pseudoplastic fluids and geometric optimization of micromixers. Concerning the first problem, tube arrangement systems were modeled such that three cases, with one, two, and four degrees of freedom were evaluated in terms of dimensionless heat transfer density. In the second problem, micromixers with cylindrical obstacles, whose vertical and horizontal positioning, were evaluated, totaling two degrees of freedom. Subsequently, the number of obstacles is also investigated, so one more degree of freedom was considered. The modeling of the described systems was elaborated and solved using numerical simulations via Computational Fluid Dynamics (CFD), through the finite volume method (FVM). Viscosity modeling for the pseudoplastic fluids was performed using the Power-Law model, while mixing modeling, in the second problem, the Species model was used. For both problems, continuity, and Navier-Stokes equations were solved. The application of the RSM methodology was done in open-source code, where the necessary experiments were designed using the Central Composite Design method, and, later, used to elaborate the polynomial model needed to create the response surfaces. Concerning the first study, it was noted that the heat transfer density is directly dependent on the distance between cylinders and that the greater the degree of pseudoplasticity of the fluid, the greater the performance in heat transfer. A significant difference in configuration was noticed when pseudoplastic and Newtonian fluids were used. For the former, the configuration tends to be more compact, so that smaller spacings and larger cylinders can be developed, contrary to the tendency presented by Newtonian fluids. Concerning the second study, it was observed that the greater the number of obstacles, the greater the mixture obtained. However, the energy required is also greater. By introducing the Mixing Energy Cost (MEC), designs with three obstacles were more efficient, while the one with seven (maximum evaluated value) had the worst index. However, the local pressure gradient is smaller for larger amounts of obstacles. By modifying degrees of freedom, it was possible to ensure that the system
evolved so that the objective of the systems (heat and mass transfer) could be increased, thus ensuring higher performance, even for simple configurations.
Wed, 15 Mar 2023 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/125052023-03-15T00:00:00ZEstudo de um coletor solar de tubo a vácuo com baixas inclinações através de CFD e proposta de correlações de transferência de calor
http://repositorio.jesuita.org.br/handle/UNISINOS/12504
Estudo de um coletor solar de tubo a vácuo com baixas inclinações através de CFD e proposta de correlações de transferência de calor
Schneider, Alexandre
Global warming is driven by the consumption of fossil fuels for energy generation,
where only 7% of energy comes from renewable sources (IEA, 2020a). In Brazil part of the energy generated is used for heating water and of the 43.1% of households that heat water only 0.96% use solar energy for this purpose (ELETROBRAS, 2020). An evacuated tube consists of two concentric tubes closed together, where a vacuum is applied. The outer wall of the inner tube receives a layer of a material that absorbs solar radiation. The commercial software ANSYS Fluent was used to perform this numerical study, adopting a three-dimensional model governed by the equations of conservation of mass, momentum, and energy. A hexahedral mesh was used with refinement in regions of the largest fluid dynamic and thermal gradients. The generated model was validated by the Grid Convergence Index method and with literature results. A case study was performed considering the variation of the gradient angle, fluid inlet temperature and heat flux. The mass flow rate was evaluated, where in the tube inclination of θ = 5° the maximum value is at a distance L = 0.17 m from the open end, the temperature variation along the tube, being the maximum value found of 3.172 K, the profiles of heat transfer coefficient by natural convection, h, in relation to the inlet temperature and the temperature variation, where it was observed that the inclination angle can reduce on average 13.3% the h, and the Nusselt number. A correlation was proposed for the Nusselt number, with a coefficient of determination of R² = 0.996, and for the temperature variation at the open end of the evacuated tube manifold, with a coefficient of determination of R² = 0.946.
Mon, 19 Dec 2022 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/125042022-12-19T00:00:00ZAnálise do design de stents arteriais coronários baseado na hemodinâmica computacional
http://repositorio.jesuita.org.br/handle/UNISINOS/12229
Análise do design de stents arteriais coronários baseado na hemodinâmica computacional
Valentim, Moisés Xavier Guimarães
Annually, thousands of people died from atherosclerosis, that is a disease caused by the
hardening of the arteries which impair blood flow within them. One of the most used treatments is the application of stents, that are devices inserted in the interior of arteries with the aim to restore blood flow to its original condition. However, a recurrent problem in this type of surgical intervention is restenosis, a new deposition of fat layers in the region of stent which causes a new obstruction. To propose improvements in design and geometry for the stents commercially used, it is used fluid mechanics applied to blood flow: computational hemodynamics. For this, this present work makes use of the theory to analyze if the chance of the cylindrical geometry (commercially used) to conical could increase the lifespan of the stent inside the artery. For this, it is used boundary conditions which simulates blood pulsation (transient regime) proposed by Vimmr et al (2012) and three different types of models for blood: Newtonian, Carreau (most commons) and Power-Law. To analyze which stent is the most efficient (minimize the occurrence of restenosis) the WSS and OSI parameters were used based in the studies in the literature. The higher WSS value and the lower OSI value, the lower the chances of fat layer or cells being deposited in the places where stents are inserted. As main results, it was found that in all situations and for all the models of blood used, the conical model is the more efficient than the cylindrical one. For the models used for blood, Newtonian and Carreau had very similar results, while PoweLaw generated very different numbers and therefore it should be further analyzed for its applications in the analyzed cases. Thus, the conical model, for the conditions simulated, has a high potential to be tested in the future as a solution to mitigate restenosis.
Thu, 29 Sep 2022 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/122292022-09-29T00:00:00ZResfriamento de placas por fluidos através de canais internos: análise da configuração e design construtal
http://repositorio.jesuita.org.br/handle/UNISINOS/12181
Resfriamento de placas por fluidos através de canais internos: análise da configuração e design construtal
Fraga, Guilherme
Vascularized plaque technology is one of the most promising in the field of thermal sciences and has been gaining notoriety for its performance in cooling and refrigeration applications. The use of tree-shaped inner tubes, parallel tubes and coils are examples of approaches found using this method of cooling solids. The objective of this work was the development of a high-performance inner tube configuration, based on the principles of Construtal Theory, with a square shape with a central reentry, which reached both the ends and the center of the plate. The solid's material is inspired by a gap-filling substrate used in the electronics industry and the cooling fluid is water. The physical system was computationally modeled as a threedimensional domain, where the equations of mass balance, momentum and energy are valid for a Newtonian fluid in permanent laminar regime. The Construtal Design Method was used to define the system, degrees of freedom, constraints, as well as the evaluation method of the system, as its configuration is modified to achieve the best thermal performance. For the analysis of the effects of the degrees of freedom and the search for the best configurations, the response surface method was used. With a variation of three degrees of freedom, systems subject to two flow rates were evaluated, featuring Reynolds numbers of 100 and 1000. The proposed configurations were numerically solved by computational fluid dynamics. It was observed that the parameter that has the greatest interference in the performance of the system is the length of the pipe in the longitudinal direction, responsible for giving shapes from
flattened, with the pipe centered at the center of the solid, to quadratic shapes, where
the pipe extends to the ends of the warm body. The results obtained allowed the
determination of geometries with performance gains of up to 44% among the simulated
cases for Reynolds equal to 1000 and 7% for Reynolds equal to 100, following the
trends projected by the temperature contour maps obtained from the method of
adopted response surface.
Thu, 29 Sep 2022 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/121812022-09-29T00:00:00ZEstudo da evaporação de filme fino de nitrogênio: uma metodologia de vitrificação para criopreservação de material biológico
http://repositorio.jesuita.org.br/handle/UNISINOS/12047
Estudo da evaporação de filme fino de nitrogênio: uma metodologia de vitrificação para criopreservação de material biológico
Steffenon, Guilherme Dahmer
Cell cryopreservation is a branch of science that describes methodologies to preserve
living cells through freezing and conservation at negative temperatures. With this in mind, some researchers study the process of cellular freezing in the most different ways, and it can be classified between slow and fast freezing (vitrification). So the present work aims to experimentally study the method of vitrification by thin film evaporation of nitrogen for cellular cryopreservation. This study has an experimental comparison between the thin film evaporation method and the immersion method, using liquid nitrogen as coolant and water as a sample in both cases. The experimental study used different test sections, with different dimensions and compositions, in order to identify the best layout to optimize the cooling rate. In addition to the experimental study, the work also developed a numerical methodology to describe the process studied through computer simulations in CFD using Ansys Fluent ® software. The numerical simulation studied considered a 2D geometry, using k-ω turbulence method and solidification method to simulate all the processes that occur in thin film evaporation. The experimental results showed a higher freezing rate in the immersion methods, presenting values of approximately 900°C/min. The thin film evaporation method, in the best case studied, found a freezing rate of 500 °C/min. Finally, the numerical simulation was also able to predict the beginning of the freezing process, demonstrating the nitrogen flow profiles, temperature variation and the solidification process of the sample.
Thu, 29 Sep 2022 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/120472022-09-29T00:00:00ZEfeito da torrefação de resíduos de Eucalyptus grandis
http://repositorio.jesuita.org.br/handle/UNISINOS/11120
Efeito da torrefação de resíduos de Eucalyptus grandis
Dias, Guilherme Igor
Torrefaction is a thermal process that occurs in the endothermic phase of pyrolysis at temperatures between 200ºC and 300ºC. The growing study of the process is related to the conversion of lignocellulosic raw materials into a “carbonized” product with the capacity to be inserted as fuel for power plants, gasifiers, combustion units, etc. The aim of this study was to verify the changes produced in the biomass from Eucalyptus grandis when submitted to the torrefaction process. Three torrefaction temperatures (200 ºC, 250 ºC and 300 ºC) with three residence times (20 min, 30 min and 40 min) were applied, and the biomass was analyzed for its Gravimetric Yield, Energy Yield and PCS. The variation in energy density, improvement in grinding and rest and slip angles of the torrefaction materials was determined, always in comparison with the fresh sample. It was observed that the temperature of the torrefaction process is the most impactful factor in modifying the physicochemical structures of the biomass, with the temperature of 300 ºC being the one that provided the most significant improvements to the material. The highest PCS obtained was for torrefaction performed at 300 ºC, showing an increase of 12.23% when compared to fresh biomass. The increase in temperature generates a material of smaller granulometry and more friable, facilitating the grinding operations, with the torrefaction carried out at 300 ºC, producing a material with a diameter 25% smaller when compared to the fresh sample. After grinding, this biomass trated at 300 ºC had a diameter 39.33% smaller when compared to the same torrefaction sample and 54.24% smaller when compared to the unground fresh sample. In relation to energy density, the increase in the apparent specific mass provided a gain of 24.85% and 28.25% for the apparent specific mass and bed. The angle of repose decreased as a result of the increase in temperature, with the slip angle showing the opposite behavior. Torrefaction proved to be a pre-treatment capable of adding energy value to the material, in addition to improving its physical characteristics, making it a more suitable fuel for insertion in energy generation systems.
Tue, 26 Oct 2021 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/111202021-10-26T00:00:00ZModelagem e simulação da estratificação térmica na camada limite atmosférica
http://repositorio.jesuita.org.br/handle/UNISINOS/10841
Modelagem e simulação da estratificação térmica na camada limite atmosférica
Schuster, Matheus Foschera
Simulations of wind flow in the atmospheric boundary layer currently carried out, despite being well developed, often disregard effects such as the different thermal stratification conditions, in order to simplify the models. Thermal stratification, however, has a significant impact on the results obtained by the simulation, especially in places where there is great daily or annual temperature variation. Thus, this research sought to develop a CFD model to better represent the flow in the atmospheric boundary layer simulated in a wind tunnel under thermal stratification conditions. To this end, the commercial software ANSYS Fluent was used, applying the large eddy simulation methodology (LES - Large Eddy Simulation), with the dynamic Smagorinsky sub-grid model, as well as the classical modeling of turbulence (RANS - Reynolds Averaged Navier-Stokes). The Boussinesq approximation was used to represent natural convection and the effects of atmospheric stratification in the vertical profiles of flow velocity and temperature were introduced through the Monin-Obukhov Similarity Theory. The developed model was applied in the simulation of flow over a steep hill, and the results obtained were compared to data from wind tunnel experiments found by Ross et al. (2004), in addition to being applied to the flow over the reduced model of a wind turbine, for a qualitative analysis of the impacts of atmospheric stratification on flow velocity and turbulence. In general, the model behaved well, and was able to satisfactorily represent the general effects induced by thermal stratification, being possible to identify variations in the velocity profile for the different cases of stratification, in addition to the impacts of the temperature gradient on the turbulent intensity of the flow. The results obtained indicate that atmospheric stability is an important factor for the flow in the atmospheric boundary layer, and should be taken into account for a better planning of wind farms.
Thu, 30 Sep 2021 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/108412021-09-30T00:00:00ZInfluência da excentricidade e proporção de massa no processo de fusão de PCM em trocadores de calor de múltiplos anéis
http://repositorio.jesuita.org.br/handle/UNISINOS/10617
Influência da excentricidade e proporção de massa no processo de fusão de PCM em trocadores de calor de múltiplos anéis
Picoli, Franco
Thermal energy storages are an important system for energy storage, having a wide range of use within engineering. Among the existing types, the latent heat ones offer advantages over the others, however, they still have limitations for their application, one of the main ones being the low thermal conductivity of the materials used for energy storage. In this study, the influence of the combination of different geometries, eccentricities and mass proportion between rings on the phase change material (PCM) fusion process in a multi-ring thermal energy store is investigated. The study was carried out by computational fluid dynamics considering a two-dimensional domain. The analyzed PCM was the RT82. For all the analyzed arrangements, the thermal exchange area and the system's PCM mass were kept constant. The numerical model used is composed by the equations of momentum, mass and energy conservation, plus the phase change model. Numerical validation was performed using experimental results taken from the literature. The results of the study reveal that the horizontal square section geometry provided the shortest melting times of the PCM comparing mass proportion between rings and equivalent eccentricities. The increase in the mass ratio between the rings containing PCM contributed to the reduction of the total fusion time in the system, mainly caused by the reduction in the amount of mass in the outer ring, consequently increasing the fusion rate in it. The eccentricity of the tubes contributed to reduce the total melting time, distributing the mass from the lower region to the upper region of the rings where the highest melting rates occur, however there is a limitation, since high eccentricity values excessively increase the amount of mass in the upper region reducing the melt rate. The combination between the increase in the ratio of mass ratio between the rings and the eccentricity helped to reduce the melting time of the PCM, and the optimal combination was the arrangement with horizontal square geometry, 𝜓 = 26/74 %/% and 𝜃 = 10 mm, obtaining a total time of 54.5 min.
Fri, 17 Sep 2021 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/106172021-09-17T00:00:00ZCo-combustão em leito fluidizado de carvão mineral com bagaço de cana-de-açúcar e casca de nabo forrageiro: avaliação fluidodinâmica e das emissões atmosféricas
http://repositorio.jesuita.org.br/handle/UNISINOS/10238
Co-combustão em leito fluidizado de carvão mineral com bagaço de cana-de-açúcar e casca de nabo forrageiro: avaliação fluidodinâmica e das emissões atmosféricas
Vuelma, Jonatan
Currently, the electricity generation is heavily dependent on fossil fuels, which emit large amounts of greenhouse gases (GHG) such as CO2, CO, NOx and SO2. One of the alternatives to reduce the emission of these gases and to insert renewable resources in the energy matrix is the use of biomass as substitute or associated with fossil fuels, like coal. In some countries, the fluidized bed technology has been used to associate biomass with coal in the generation of thermal energy. However, a step prior to its implementation on an industrial scale consists on the evaluation of the fluid dynamics behavior and the impact of the biomass on the atmospheric emissions in the process of co-combustion with coal. In this work, the minimum fluidization velocity of mineral coal and biomass mixtures was evaluated in three fluidized bed reactors with different scales and geometries. Mixtures of coal from the Candiota mine in Rio Grande do Sul were used, with two distinct regional biomasses: sugarcane bagasse and Raphanus Sativus L. husks, in proportions of 10%, 30% and 50% of volume. The biomasses were also characterized by different techniques that included heat value, immediate and elementary analysis, being possible to observe similar values of heat value between the biomasses 20,150 kJ / kg and 17,100 kJ / kg and the ash contents were of 4.88% and 3.56% for sugarcane bagasse and Raphanus Sativus L. husks, respectively, ash values are considered relatively low. To evaluate the impact of biomass combustion on atmospheric emissions, combustion tests were carried out on a bench unit with continuous NOx and SO2 emission monitoring. It was verified that the release of SO2 is high in the combustion of coal (164 ppm). It is possible to obtain lower amounts in the combustion of the Raphanus Sativus L. husks (23 ppm) and, mainly, with the cane bagasse (3 ppm). The results were promising for pilot-scale evaluation of the process, in order to technically and economically evaluate the process of co-combustion of these biomass residues in an industrial unit.
Thu, 17 Aug 2017 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/102382017-08-17T00:00:00ZEstudo de fluidização de biomassas lignocelulósicas visando a proposição de um modelo empírico físico
http://repositorio.jesuita.org.br/handle/UNISINOS/10166
Estudo de fluidização de biomassas lignocelulósicas visando a proposição de um modelo empírico físico
Ocanha, Enzo Schlottfeldt
Thermal energy conversion industries have been increasingly employing fluidized bed combustion technology, as it currently is one of the most efficient and feasible alternatives for a low carbon scenario. Fluid dynamics researches of fluidized beds provide valuable information for the design and operation of these systems. However, fluidization mathematical modeling, even for homogeneous particles, is a complex subject: it involves modeling gas flow, solids flow and the interaction between them. In the case of mixtures of particles with different physical properties, predict fluidization behavior is a great challenge. Usually empirical correlations are used to determine design parameters, such as characteristic fluidization velocities. The objectives of the present work were to compare characteristic fluidization velocities obtained experimentally with predictions of correlations from literature, and to verify if other physical and physicochemical parameters could be more appropriate for prediction of these velocities. Biomasses evaluated were sugarcane straw and bagasse, eucalyptus wood, rice husk and apple tree branches, in mixtures with sand in the following proportions: 20, 40, 60 and 80 percent of biomass volume fraction. Materials were characterized by their mean particle size (Sauter and Feret methods), true density, loose and tapped bulk densities, chemical, proximate and elemental compositions, higher heating value, repose angle, sphericity and aspect ratio. A bench scale reactor, with 94 mm internal diameter, was used to fluidize biomass and sand mixtures. Measured variables were air flow rate and pressure drop along the bed. Multiple linear regression was performed on SPSS 22 software. Materials characterization showed that biomasses present similar elemental composition, but differences in chemical and proximate compositions. True mass densities varied between 1002 kg/m³ for straw and 2587 kg/m³ for sand, and loose bulk densities varied between 98 kg/m³ for straw and 1499 kg/m³ for sand. Mean Sauter diameter of particles ranged from 363 μm for sand to 931 μm for straw, while Feret mean diameter ranged from 378 μm for sand to 2718 μm for straw. Fluidization tests showed minimum fluidization velocities Umf between 0.11 and 0.38 m/s, and complete fluidization velocities Ucf between 0.18 and 0.82 m/s for mixtures. Biomass and sand mixtures fluidized well in proportions up to 60% in volume of biomass. For proportions above this limit, there was intense formation of preferential channels and the occurrence of agglomerations in bed. Tested correlations were unable to predict Umf and Ucf in any situation, presenting great dispersion of results and relative errors higher than 60%. Multiple linear regression indicated mixtures bulk densities and repose angles as the most relevant parameters in the prediction of characteristic fluidization velocities. The two developed correlations from these properties obtained good results in prediction of these velocities: the adjusted R2 coefficient obtained at Umf prediction was 0.782, while at Ucf prediction it was 0.855. For Umf, on 90% of mixtures the relative error found was smaller than 24.3%, while for the Ucf on 90% of cases this error was smaller than 22.5%. Proposition of repose angle as a predictor for characteristic fluidization velocities are unprecedented, as well as the acknowledgment of bulk density as the most relevant parameter in the prediction of these velocities.
Thu, 04 Jan 2018 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/101662018-01-04T00:00:00ZAnálise experimental de um ciclo de refrigeração com uso de ejetor bifásico e separador de líquido do tipo T
http://repositorio.jesuita.org.br/handle/UNISINOS/10097
Análise experimental de um ciclo de refrigeração com uso de ejetor bifásico e separador de líquido do tipo T
Gonçalves, Anselmo Goulart
This work presents an experimental study of a refrigeration cycle with a two-phase ejector for energy recovery with the R-134a refrigerant, specifically the cycle proposed by Gay. This cycle was carried out with a liquid separator with T-junction and a visualization section designed to analyze the flow patterns. Experimental tests were performed analyzing the refrigerant charge in the system and its influence on the cycle parameters. With a refrigerant load of 4,600 g, an analysis of the compressor rotation, the inlet air temperature in the evaporator and the influence of the expansion valve opening and its consequences on the system was carried out. With the analysis of the refrigerant charge in the system, it was observed that the amount of mass considerably influences the power of the compressor and the thermal power of the condenser, but it is not very effective in the flow of the secondary nozzle. The analysis of the influence of compressor rotation and temperatures, together with a thermographic analysis, allowed the identification of reverse flow in the ejector. The liquid separator presented in all experimental tests stratified flow in the inlet section and phase separation in the vertical section, being possible to identify through images the phase separation in its body.
Tue, 29 Jun 2021 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/100972021-06-29T00:00:00ZEstudo numérico e experimental de conforto térmico em cabine de ônibus
http://repositorio.jesuita.org.br/handle/UNISINOS/9960
Estudo numérico e experimental de conforto térmico em cabine de ônibus
Vidor, Bruno Vinícius
The research around thermal comfort is motivated by the improvement of the quality of life, safety for activities that require attention, energy efficiency, competitive differential for the industry, and various activities in which the human being is inserted. Computational fluid dynamics (CFD) can be used to improve the geometries and operating conditions of systems in order to improve thermal comfort and contribute to the advancement of science and technology. The work presents a numerical and experimental study of the thermal comfort of a bus driver's cabin, aiming to validate the numerical implementation as a method of analysis and improvement of this type of system. In the first part, this work presents a literature review, which demonstrates how thermal comfort has been approached in association with CFD techniques. In the second part, it is proposed to investigate, through numerical and experimental methods, the air flow, its speeds and temperatures, in the environment of a bus driver's cabin, in order to relate them to the thermal comfort in this environment. A commercial CFD code based on the finite volume method was used, and the results were compared with experimental measurements. The validation made it possible to define good modeling practices for the system in question. The determination of the thermal comfort indexes (PMV-PPD) and the fields of temperatures and air speeds allowed the elaboration of recommendations aimed at greater thermal comfort for the design of bus cabins. The developed numerical model presented good results observing the comparisons with the experimental measurements. The average absolute difference obtained for the temperature was 0.8 °C while for the air velocity it was 0.04 m/s. Through the numerical results, the PMV-PPD indices demonstrate that 92.33% of the individuals would feel comfortable with the environment, which represents a PMV index of -0.3582. The experimental results of average temperature and air speed demonstrate that 93.27% would feel comfortable with the environment, which represents a PMV index of -0.2882. The methodology adopted for the evaluation of thermal comfort through numerical simulations allows to provide comfortable environments to human beings through the study of improvements in different projects.
Thu, 06 May 2021 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/99602021-05-06T00:00:00ZAvaliação da co-combustão de carvão mineral com serragem de eucalipto em leito fluidizado borbulhante
http://repositorio.jesuita.org.br/handle/UNISINOS/9893
Avaliação da co-combustão de carvão mineral com serragem de eucalipto em leito fluidizado borbulhante
Cunha, Marcelo Gregory
It is estimated that coal will remain, for the next few years, the main input to produce electricity. Thus, there is a need to study its co-combustion with biomass, a renewable and abundant fuel, to mitigate the environmental impacts caused by emissions of this fuel. This study aimed to analyze the effect of biomass content on the co-combustion of biomass and coal in a bubbling fluidized bed reactor in laboratory scale. The biomass used is eucalyptus sawdust from Rio Grande do Sul and the coal comes from a deposit in Colombia. The cold fluid dynamic behavior, the physical and thermal characteristics of the particles, the operational conditions of the reactor, as well as the emissions of CO, CO2, NO and SO2 gases were evaluated. It was possible to observe that the minimum fluidization velocity increased as higher biomass ratios were added to the mixture. Chemical and thermal analyzes of coal identified a low ash content (approximately 7%) and a high calorific value (28.1 MJ/kg). The temperatures inside the bed remained stable, between 800 and 900 °C, for all mixtures and excess air analyzed. The addition of biomass to the mixture, in proportions of 10 and 25% by mass, increased the average bed temperature due to the rapid devolatilization of the biomass volatile content verified in the TGA tests. In the freeboard region, temperature fluctuations were observed, mainly in the mixture with 25% of biomass. The addition of 10 and 25% of biomass proved favorable for CO emissions for most of the reasons tested. The addition of 10% biomass promoted a better efficiency of the combustion process, and this fact was observed based on the CO2 emission closer to the ideal. As for the NO and SO2 gases, the addition of biomass resulted in a slight reduction in emissions when compared to the singular burning of coal, which can be explained by the lower content of N and S elements present in the biomass.
Fri, 30 Apr 2021 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/98932021-04-30T00:00:00ZCaracterização dos padrões de escoamento na ebulição do isobutano em um micro canal
http://repositorio.jesuita.org.br/handle/UNISINOS/9572
Caracterização dos padrões de escoamento na ebulição do isobutano em um micro canal
Dias, Isadora Cardozo
New applications for refrigeration systems are emerging all the time, as industrial manufacturing processes, nuclear, aerospace and other systems that generate heat during their use are always being developed, due to this need, compact heat exchangers need to be improved, requiring studies related to thermal exchange and improvements in energy efficiency. Com pact systems are studied to meet these demands, so combining the fluid phase change process with the development of compact mini and micro channel systems becomes increasingly nec essary. The present work analyzed data on the boiling of the isobutane refrigerant (R600a) in a horizontal micro channel (internal diameter of 1 mm), which makes up an experimental bench made up of three sections (pre-heating, testing and visualization), as well as several sensors for measuring temperature, flow, pressure and an optical sensor. Tests were carried out with variations in mass velocities (520 m kg 2s ∼ 1220 m kg 2s ) and heat flow (10 kW m2 ∼ 60 kW m2 ) and the acquisition of temperature, pressure and flow data for further treatment. Flow images were also recorded under different conditions and the signals from an optical sensor associated with these were recorded. Thus, the flow patterns were assessed by identifying the images and also by treating the optical sensor data with the Fast Fourier Transform (FFT) methodology combined with Power Spectral Density (PSD), as well as treating the images of the patterns to determine the longitudinal area occupied by the steam in the tube. For the analysis of the characteristic frequencies, the PSD method was used, the void fraction, flow velocities and vapor title were calculated and the images treated with an python algorithm developed in this work. For the lowest values of mass velocity (G), the highest vapor title were achieved, and all patterns of isolated, elongated, slug, churn and annular bubbles were observed. While for the higher G, even when a greater heat flow was applied to the test section (TS), the vapor title were reduced and the predominantly observed patterns were intermittent (slug and churn) and annular. In the frequency analysis, similar values of frequencies (where the highest power spectral densities are concentrated) were found between the same patterns for different tests performed, for the pattern of isolated bubbles the highest value occurs at the frequency of 15 Hz and for the churn patterns and wavy annular for values below 5 Hz, going up to the frequency of 10 Hz. The image processing through the developed algorithm was able to identify the longitudinal área occupied for the patterns of isolated bubbles and elongated bubbles.
Fri, 03 Jul 2020 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/95722020-07-03T00:00:00ZAvaliação do biocarvão de casca de banana obtido via pirólise para aplicação em solos agrícolas
http://repositorio.jesuita.org.br/handle/UNISINOS/9569
Avaliação do biocarvão de casca de banana obtido via pirólise para aplicação em solos agrícolas
Righeto, Guilherme Bampi
The generation of waste by the agricultural sector, driven by the increase in population,
has been a challenge in terms of its management, given the large amount of bio-waste
produced, which can reach 40% only in the fruit industry. Banana peel, residue from
banana consumption, is basically composed of the lignocellulosic structures found in
most agricultural biomasses: cellulose, hemicellulose, lignins, extracts and other
elements such as K, found in large quantities in the fruit and one of the macronutrients
necessary for soil fertility. The conversion of banana peels through slow pyrolysis can
form more stable structures and which, when incorporated into the soil, can promote
an improvement in their quality and possible increase in crop yields. In this sense, this
work sought to evaluate the characteristics of the biochar formed from the pyrolysis of
banana peel in two heating profiles at the pyrolysis temperature of 370 °C at heating
rates of 11 °C/min and 35 °C/min determined with the aid of a computational model for
a potential application in agricultural soils. The biochars produced were characterized
in order to determine the hydrogen potential (pH), electrical conductivity (EC), cation
exchange capacity (CEC), morphology, surface area, atomic ratios C/N, H/C and O/C.
The results showed a highly alkaline structure, with an average pH value of 12.60; as
well as a CTC of 511 mmol/kg which suggests a good potential for application as a soil
conditioner. It was possible to conclude that, the temperature increases until the
heating bands of the profiles of the pyrolysis performed formed a stable biochar
considering its lower atomic ratios, to the point that it was possible to observe an
increase in its surface area and amount of pores in its structure.
Tue, 23 Feb 2021 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/95692021-02-23T00:00:00ZDesign construtal de bifurcações em forma de Y para escoamentos de fluidos de Carreau
http://repositorio.jesuita.org.br/handle/UNISINOS/9547
Design construtal de bifurcações em forma de Y para escoamentos de fluidos de Carreau
Pellejero, David Cristopher
This work investigates the optimal geometries for bifurcations subject to pseudoplastic non-Newtonian fluid flows, and to analyze how the fluid rheology has effects on the configurations and performance of Y-shaped bifurcations. The analysis is based on minimization flow resistance, with the definition of the ratio of diameters, length ratio and bifurcation angle as degrees of freedom and design parameters and imposition of restrictions according to the Design Constructal method. The fluid was modeled using the Carreau equation, and the effects of Carreau number, viscosity ratio and flow index were analyzed. The flows were solved numerically using the Finite Volume Method and the ANSYS® Fluent software. The mathematical model was verified with results published in the literature, and the computational mesh was analyzed by the GCI method. The Response Surface optimization algorithm was used to search for the minimum flow resistance and the optimal values for the design variables. A three-level factorial design was used to verify the effect of the rheological parameters on these results. From the results obtained, it was found that the power index is the rheological parameter that has the greatest effect on the configuration of the optimal geometry, affecting both the length ratio and the ratio of diameters to the minimum flow resistance. statistically significant effect was only on the ratio of diameters. This, in turn, proved to be the geometric parameter that had the greatest influence on the flow resistance behavior. These results corroborate the thesis that the analysis for systems with non-Newtonian fluids should consider the rheology of fluids to obtain their best performance.
Fri, 25 Sep 2020 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/95472020-09-25T00:00:00ZEstudo do desempenho de um conversor de energia tipo coluna de água oscilante utilizando um modelo computacional tridimensional e design construtal com três graus de liberdade
http://repositorio.jesuita.org.br/handle/UNISINOS/9498
Estudo do desempenho de um conversor de energia tipo coluna de água oscilante utilizando um modelo computacional tridimensional e design construtal com três graus de liberdade
Bloss, Vinícius
Recently, the oceans have been seen as a promising source of renewable
energy. Theoretically, the oceans could offer enough energy to supply the entire world
demand. Among the technologies available for energy conversion from the oceans,
the Oscillating Water Column (OWC) type devices stand out, which are characterized
by a chamber, in which the water oscillates inside in a movement similar to a piston.
This movement moves the air to a chimney, where a turbine is attached. The passage
of air through the turbine promotes the conversion into mechanical energy. In the
present work, the study of the performance of a 1:15 scale OWC type converter was
performed using a three-dimensional computational fluid dynamics model. The
analysis was based on the Constructal Design Method. In this approach, energy is the
quantity that flows through the system, whose purpose is the maximum rate of
conversion of wave energy into mechanical energy. Three degrees of freedom were
used: the ratio of height to length of the hydropneumatic chamber (H1/L), the ratio of
the height of the chimney to its diameter (H2/d), and the ratio of the width of the
hydropneumatic chamber to the width of the wave tank (W/Z). The effect of different
combinations between degrees of freedom for a typical wave of the southern region of
the Brazilian coast was investigated. Conversion efficiency was used as a performance
parameter. Computational modeling of the system was performed, using
computational fluid dynamics software based on the finite volume method (FVM), using
the Volume of Fluid (VoF) modeling for the interface between the gas and liquid
phases. In a first analysis, it was observed that the height of the chimney always has
a positive effect on the efficiency of the system. However, only workable values were
selected for this degree of freedom, limiting the subsequent analyzes to two degrees
of freedom, H1/L and W/Z. Through a Design Experiment of the Central Composite
Project type, different combinations of degrees of freedom were simulated, allowing
the construction of Response Surfaces and correlations for the efficiency of the system
depending on the degrees of freedom width and height of the chamber, as well as the
optimization of the system based on the Response Surfaces. In the tests carried out,
the efficiency of the OWC device varied from 1.48% to 19.32% in the worst and best
case, respectively.
Thu, 15 Oct 2020 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/94982020-10-15T00:00:00ZAnálise numérica da influência de um conjunto de aletas com diferentes inclinações e posições em uma cavidade retangular preenchida por PCM em processo de fusão
http://repositorio.jesuita.org.br/handle/UNISINOS/9390
Análise numérica da influência de um conjunto de aletas com diferentes inclinações e posições em uma cavidade retangular preenchida por PCM em processo de fusão
Borahel, Rafael Da Silveira
Through the use of the finite volume method, the numerical study of the melting process of lauric acid contained in a finned rectangular cavity was conducted in this work. In the cavity, two longitudinal fins of rectangular shape are attached to the heated surface of the system under different inclinations. The aims of this study was (i) determine which metals are most suitable to be used in the fins; (ii) investigate the possibility of computational modeling of the fins to be performed in an idealized way, where the perimeter of the fins has identical temperatures to that of their base; (iii) analyze the melting process for a range of different inclinations (θ) used in the installation of the fins to the heated surface of the system; (iv) identify the existence or not of a more adequate inclination; (v) understand the effects caused by the different inclinations under the convection heat transfer that occurs inside the system; (vi) evaluate the effect of the vertical position of installation of the fins under the melting process intensified by them and (vii) determine the most suitable spacing to be allowed between the fins. To achieve the proposed objectives, two-dimensional transient numerical simulations, conducted in the commercial software ANSYS Fluent 19.2, were used to solve the proposed problem. In this software, unstructured computational meshes were used for the spatial discretization of the problem, while different time intervals were tested for temporal discretization. The mathematical model was composed by the differential equations of continuity, energy and momentum, plus the enthalpy-porosity method used to treat the lauric acid melting. The results obtained demonstrated that the implemented model is adequate for the proposed study and aluminum and copper are the most suitable materials for the fins, while steel was shown to be harmful to the heat transfer. The inclinations used in the installation of the fins influenced the process in different ways, proving that for the most initial and intermediate stages θ = 90° it considerably accelerated the melting, while higher θ values did better in the more advanced stages. Basically, there is no more suitable value for θ, but a range of possible values, which vary between 90 and 115°. In terms of performance, the lower the installation position of the fins, the faster the melting occurs.
Sun, 23 Aug 2020 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/93902020-08-23T00:00:00ZDesign construtal de bifurcações de tubos com escoamentos de fluidos não newtonianos de Carreau e de Bingham
http://repositorio.jesuita.org.br/handle/UNISINOS/9389
Design construtal de bifurcações de tubos com escoamentos de fluidos não newtonianos de Carreau e de Bingham
Turmina, Leonardo Balbinot
Wed, 01 Jul 2020 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/93892020-07-01T00:00:00ZEstudo numérico de um conversor Coluna de Água Oscilante através do método Design Construtal
http://repositorio.jesuita.org.br/handle/UNISINOS/9388
Estudo numérico de um conversor Coluna de Água Oscilante através do método Design Construtal
Cardozo, Camila Fernandes
Wave energy converting devices take advantage of the movement of water to generate electricity, converting potential and kinetic energy into electrical. The present work focuses on the study of an Oscillating Water Column (OWC) converter, which uses the vertical movement of the waves inside a semi-submerged chamber to obtain high speed air through a chimney, in which an electrical generator must be connected. A three-dimensional model of the OWC device, with a rectangular chamber and a cylindrical chimney, in a 1:15 scale, was investigated with the objective of maximizing the hydrodynamic efficiency from geometric variations, using the Constructal Design method. The problem was solved numerically with the Fluent software, which uses the Finite Volume Method, along with the Volume of Fluid model for multiphase flow. The parameters analyzed were the chamber submersion level (H3/h), ratio between the width of the chamber and the width of the computational wave tank (w/Z) and ratio between the height and the diameter of the chimney (H2/d). For the studied cases, the highest efficiency values were obtained when H3 ≈ h, W ≈ Z and H2 d. However, the pressure fields inside the device showed a symmetrical behavior along the width w, suggesting that, for the cases studied, the parameter w/Z had a low influence on the efficiency values. In contrast, geometric variations in the chimney (H2/d) showed more significant efficiency gains, a decrease in internal air recirculations and more uniform velocity and pressure fields. Among all the cases analyzed, the worst and the best efficiency values obtained were 0.14% and 49.85%, respectively.
Thu, 25 Jun 2020 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/93882020-06-25T00:00:00ZEstudo de indicadores de eficiência energética na usinagem integrando monitoramento de energia com sistema de execução de manufatura
http://repositorio.jesuita.org.br/handle/UNISINOS/9277
Estudo de indicadores de eficiência energética na usinagem integrando monitoramento de energia com sistema de execução de manufatura
Blos, Tiago Miguel
Energy efficiency in manufacturing is an increasingly discussed issue in the pursuit of reducing energy costs and reducing the negative environmental impact of industrial processes. Thus, it seeks to produce more with less energy and for this it is essential to have full knowledge of consumption in production. In order to work on energy efficiency improvement in manufacturing, it is necessary to have energy management and, to reach that, is important to have an energy monitoring of productive resources. To evaluate collected data by monitoring system, are needed Key Performance Indicators (KPIs) that can provide decision-making support for process improvement that promote better energy efficiency. These energy efficiency KPIs can receive information by cross-checking energy monitoring system databases with production monitoring systems such as the Manufacturing Execution System (MES), which can provide real-time information of the resources, products and production. In this context, this work proposed the application of eight KPIs that could be used integrating data from an energy monitoring system with a production monitoring system. Firstly, was made a study of the main energy KPIs in manufacturing and to validate these eight indicators, an experimental study was conducted to generate data that would feed these indicators and allow an evaluation and discussion of their relevance. The experimental study of this work was divided into two parts, the first for validation of indicators at product and process level and the second at production level in a machining process. The construction of the experimental study was carried out using Taguchi's Design of Experiments (DOE) methodology in nine samples with different combinations of values for three different cutting parameters (depth of cut (Ap), feed (Fn) and cutting speed (VC)). The results obtained show that the most relevant KPIs were the indicator of direct energy and the indicator of energy efficiency in performance. The direct energy KPI has the sample with the most severe cutting conditions and the shortest cycle time as the one with the best energy efficiency, with 167 Wh less energy consumption than the sample with milder cutting conditions. The energy efficiency indicator on performance, on the other hand, presented the impact of energy waste when there is low performance in production and the result of the sample with a shorter cycle time shown an efficiency of 64 percentage points higher than the sample with a longer cycle time.
Thu, 23 Jan 2020 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/92772020-01-23T00:00:00ZConstructal design of an idealized arterial bypass graft subjected to Newtonian and non-Newtonian blood flow
http://repositorio.jesuita.org.br/handle/UNISINOS/9276
Constructal design of an idealized arterial bypass graft subjected to Newtonian and non-Newtonian blood flow
Dutra, Rafael Fernando
Arterial bypass grafts tend to fail after some years due to Intimal Hyperplasia – an abnormal proliferation of smooth muscle cells that leads to restenosis and graft occlusion. In this regard and based on the Constructal Design method, this dissertation, that is presented in the form of two articles, seeks to investigate the effect of geometric parameters and the influence of Carreau rheological parameters on the flow through a bypass graft circumventing an idealized, partially-stenosed coronary artery. The computational model assumes steadystate fluid flow through an idealized model for a partially stenosed artery with a bypass graft. A Computational Fluid Dynamics model and a Response Surface Methodology were employed to assess the effects of bypass geometry on pressure drop. The first article presented the analysis for a Newtonian fluid. As the diameter ratio D1/D increased and the junction angle α decreased, the pressure drop decreased and so the dependence of pressure drop on the stenosis degree. The effects of diameter ratio were more pronounced than those of junction angle on the velocity field and wall shear stress. The optimum point for all cases was D1/D,opt equal to 1 and α,opt equal to 30°, which is corroborated by previous studies. In a second article, the differences in between the Newtonian and non-Newtonian results were presented, through the analysis of the influence of rheological parameters of the Carreau model for blood. All the response surfaces generated for both the Newtonian and non-Newtonian cases presented a great similarity. The results obtained demonstrated that non-Newtonian rheological parameters did not influence neither the shape of the response surfaces nor the optimum points found, although they have a great impact on pressure drop, mainly the parameters 𝜂∗ and n. Besides, it was also evaluated the effects on velocity and wall shear stress caused by the variation of rheological parameters, where, 𝜂∗ and n, appear to have a more pronounced influence than . Finally, the results found in this dissertation demonstrated that the application of the Constructal Design method in hemodynamics might be a good alternative to provide configurations with enhanced performance and to provide valuable results to the understanding of biological flows.
Mon, 06 Apr 2020 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/92762020-04-06T00:00:00ZBalanço de massa e energia da produção de placa polimérica reforçada com fibra de coco
http://repositorio.jesuita.org.br/handle/UNISINOS/9275
Balanço de massa e energia da produção de placa polimérica reforçada com fibra de coco
Zaro, Janiel Rodrigo
The processing of residues, with a view to obtaining raw materials, is in line with the concept of circular economy and can make it possible to reduce energy consumption, CO2 emissions and negative environmental impacts associated with the disposal of these residues since these materials can replace others of satisfactorily. In this way, considering the amount of residues from coconut consumption, it is imperative to find alternative uses for the amount of post-consumption coconut mass discarded irregularly on the Brazilian coast, or even from industrial processes for removing edible material from the coconut fruit. From this awareness of the recycling of post-consumption green coconut, work has emerged that highlighted the possibility of extracting the fibers from the fruit, which can be used in various applications, as a raw material in polymeric plates in the condition of reinforcing agents. However, the objective is to verify if the processes necessary for the processing of post-consumption green coconut in order to obtain fibers do not compromise the technical, environmental and economic viability of this raw material, considering it as a raw material in the production of a polymeric plate of Poly (lactic acid) PLA resin. Based on the methodology of the life cycle assessment (LCA), the mass and energy balance of the processes involving the processing of post-consumer coconut waste, the production of the composite and the making of the polymeric plate was carried out, in order to allow the quantification of the flows that make up the Life Cycle Inventory (LCI) of this production chain, which allowed to verify that the Embedded Energy (EE) of Coconut Fiber (FC), considering the process of improvement on a laboratory scale was 47.09MJ / kg, where 98.3% of the energy spent is related to the drying process of the fibers, and the rest to shredding, pressing and cutting the coconut. The EE of the polymeric PLA resin plate and reinforced with FC has an EE of 31.27 MJ / UF. The use of CES Edupack material selection software to simulate and compare polymeric PLA plates reinforced with FC, fiberglass, Carbon, and other Natural Fibers (FN) made it possible to verify that CF has an energetic and mechanical behavior similar to the available FN in the market. In order to qualitatively verify the main aspects and impacts inherent to the post-consumption coconut processing processes, as well as in the production of the composite and in the manufacture of the polymeric plate, the evaluation was carried out using a spreadsheet of aspects and impacts evaluated by specialists. It was identified that the main aspects inherent to the studied processes are the consumption of electric energy and the generation of residues, since the CF represents only 5.7% of the processed coconut mass, by-products such as powder and LCCV, which represent 24, 5 and 40.6%, respectively, need solutions aligned to their destination or even recovery. Among the negative environmental impacts analyzed, the potential for global warming, acidification, eutrophication and land use modification were highlighted.
Wed, 22 Jan 2020 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/92752020-01-22T00:00:00ZAnálise do escoamento monofásico de água em microcanais: desenvolvimento e caracterização de um trocador de calor para o resfriamento de sistemas eletrônicos
http://repositorio.jesuita.org.br/handle/UNISINOS/9274
Análise do escoamento monofásico de água em microcanais: desenvolvimento e caracterização de um trocador de calor para o resfriamento de sistemas eletrônicos
Gomes, Bruna Evelin
There is an industrial interest in research and development of microchannel heat exchangers due to the need for heat dissipation in compact systems. Cooling electronics is an example of an application that requires high heat dissipation applied, enabling a safe operating temperature. For the design of a microchannel heat exchanger, look for a minimum pressure loss, or maximum heat transfer, and an adequate and uniform temperature distribution. The present study is aimed at the development of a microchannel heat exchanger for use in electronic systems. The Constructal Design Method concomitant with an optimization were used to find the best performing geometry design, the one that allows the least flow restrictions. Straight channel geometry and branch channel level Y-channel geometry were evaluated and compared by numerical simulation, considering the temperature distribution, heat transfer coefficient and pressure loss. The geometries were fabricated in 3D printing on a silver alloy and evaluated on an experimental bench. Microchannel heat exchangers are characterized with liquid water flow in a single-phase state. The data obtained are pressure, temperature, flow rate and heat flux. The flow was laminar with Reynolds from 163 to 628, with mass flux in the range of 355 to 1,388.5 kgm-2s-1 and heat flux of 14 to 19 Wcm-2 for rectangular geometry. For Y-channel geometry with a branch level, Reynolds was in the range of 196 to 752, mass flux of 533 to 2,073.5 kgm-2s-1 and a heat flux of 16.5 to 23.5 Wcm-2. The Y-channel geometry enabled greater heat transfer with a greater pressure difference compared to channel geometry straight. For channel geometry straight, the convective heat coefficient was 14.2 kWm-2K-1 and the pressure loss was 7.2 kPa. While the Y-channel geometry, the convective heat coefficient was 24.3 kWm-2K-1 and the pressure loss was 15.9 kPa. Thus, increased heat transfer in exchange for increased pressure loss.
Wed, 22 Jan 2020 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/92742020-01-22T00:00:00ZEstudo numérico do efeito da geometria de aletas em armazenadores de calor de tubos concêntricos em processo de fusão de ácido láurico
http://repositorio.jesuita.org.br/handle/UNISINOS/9082
Estudo numérico do efeito da geometria de aletas em armazenadores de calor de tubos concêntricos em processo de fusão de ácido láurico
Spengler, Fernando Claudio
Thu, 05 Sep 2019 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/90822019-09-05T00:00:00ZEstudo e análise do espectro solar simulado a partir de parâmetros atmosféricos usando o software SMARTS
http://repositorio.jesuita.org.br/handle/UNISINOS/9054
Estudo e análise do espectro solar simulado a partir de parâmetros atmosféricos usando o software SMARTS
Boneberg, Bruna Steil
Over the years, there has been an increase in population growth rate and improved quality of life. In the search for energy alternatives to meet current and future demand for energy, photovoltaic solar energy emerges as a solution. So, the present work presents the study and analysis of simulated solar spectra aiming to show that the values measured in the soil by the spectroradiometer (Cachoeira Paulista / São Paulo) are similar to the values obtained by the SMARTS simulation software, as well as to identify if there are variations in the curves obtained for eighteen cities in the State of Rio Grande do Sul. The methodology consists in comparing and analyzing field-measured data with simulated data (SMARTS v.2.9.5) for a city in the State of São Paulo; and obtaining instantaneous irradiance values (global and direct component) for the solstices and equinox months considering: slope with the surface equal to zero, air mass at 12 o'clock on the average day of the month under analysis and the mean atmospherics parameters values of the month. The results related to the comparison between the data measured by a spectroradiometer and the data simulated by SMARTS show a consistency rate of 87,33 ± 2%. In the analysis of variation, it can be seen that among the wavelengths from 390 to 770 nm there is less oscillation between the simulated data and measured in soil. Still, the instantaneous irradiance values obtained for the municipalities did not show significant variations, which was expected considering the solar map of the State of Rio Grande do Sul, and therefore, a spectrum was generated from the average of these eighteen cities. In conclusion, there is no similarity between the values of the atmosphere parameters used by the reference spectra within the values found for the State of São Paulo, State of Rio Grande do Sul, or any part of the Brazilian territory and finally, the simulations were shown
reliable.
Mon, 12 Aug 2019 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/90542019-08-12T00:00:00ZEficiência energética em estações elevatórias: Diagnóstico hidroenergético de uma instalação fornecedora de água bruta para posterior tratamento e distribuição de água tratada para dois municípios
http://repositorio.jesuita.org.br/handle/UNISINOS/9053
Eficiência energética em estações elevatórias: Diagnóstico hidroenergético de uma instalação fornecedora de água bruta para posterior tratamento e distribuição de água tratada para dois municípios
Steffens, Daniel Rocha
This work aims to evaluate the operational/financial current situation of a raw water lift station, wich is part of an integrated treated water supply system for two big cities in south of Brazil – hydropower diagnosis. The facility is composed of five motor-pump sets, 560 kW rated power each, wich are triggered according to the operational seasonality. In the project setup, two motor-pump sets were operational reserves and, therefore, even three machines were actionated in parallel, connected to the same output pipe. Since January 2016, because of a higher flow operational need available to the supply system, one of the two standby equipment was put into operation thus totaling up to four jointly operated equipment. With the increase of raw water captured volume, in which the forth equipment was put in operation without a detailed analysis of this activity impact facing to the head losses and, according to the relatively high electric power bills values, it was decided to carry out a multidisciplinary (hydraulic, mechanics, electric, operation and simulation) study aiming the decrease of the electric power bills. The hydropower analysis was focused, basically, looking for cadastre informations (project and field) of the equipment and facilities; in the performance tests and in the motor-pump sets sequencing tests; and in the compilation and in the operational annual data analysis. The study has made it possible to find distinct results, such as: performance determinations of each motor-pump sets and the facility as a whole, as well as the most effective sequencing according to the applicable operational configurations; operational data collection during a period of one year that resulted in the determination of the facility performance indicators; valuation of head losses and the system operational speed; the construction of a hydraulic simulation model in software, calibrated in field, wich allowed the taxes framework analysis as provided by the normative resolution nº 414, from september, the ninth, 2010, according to ANEEL and the operational scenario simulations to establish possible operational/financial gains with and/or without investments. As examples of easily reachable results, only administrative/contractual ones, among others, can be highlighted: 52.327,00 R$ year-1 (-0,96 % of the total energy consumption) – just switching off the fourth equipment at the high peak period; 201.312,00 R$ year-1 (-18,60 % of the contracted demand) – when the contracted demand is changed at the high peak period from 2.150 kW for 1.750 kW; and, 156.728,52 R$ year-1 (-2,89 % of the total energy consumption) – by the optimized selection of the motor-pump sets for the more efficient combinations. Talking about the significant investments, it was diagnosed that the facility has a considerable portion of wasted power, caused by head losses in the pipes, that go much beyond what is considered inevitable/economic. This is explained because the equivalent diameter of the system adductors has a value of 931,2 mm facing an optimal/economic, probable, obtained through the Bresse equation, of 1.350 mm. Moreover, the roughness inadequate values of the pipes, after years of usage, has significant impact in the head losses values too. Therefore, with R$ 289.036,23 (substitution of the five motor-pump sets suctions, four pump rotors machining and the adductor roughness repairs, using pigs), 449.685,45 R$ year-1, or 8,28% of the total facility consumption are estimated to be saved, maintaining the current system flow rates and with a return on investment less than one year. Regarding to the electromechanical devices, the performances occurred as expected. However, the pump types currently installed never reach the maximum sustainable yield conditions at any operational points. Proposing the replacement of the motor-pump sets for another models, the performances, in the manometric heights average values established through hydropower diagnosis would be, in different operational conditions, always closer to the maximum viable. For those alterations, the expected return has been estimated in, approximately, five years considering the replacement of three pumps and three electrical motors, wich is economically viable.
Mon, 26 Aug 2019 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/90532019-08-26T00:00:00ZDesenvolvimento de uma bancada de testes para avaliação do desempenho térmico de um concentrador Fresnel linear
http://repositorio.jesuita.org.br/handle/UNISINOS/8919
Desenvolvimento de uma bancada de testes para avaliação do desempenho térmico de um concentrador Fresnel linear
Moreira, Diego Ramos
Among concentrators, linear Fresnel reflectors (LFR) have become an attractive solar power technology for being suitable for use in heating and cooling systems of buildings, domestic water heating and steam generation for industries. Conduction of performance tests is of great importance for the development and establishment of thermal solar concentrators. Existing standards prioritize testing for flat solar reflectors and show technical limitations in established methods for thermal performance analyses of concentrators. In this way, the development of test procedures is necessary, especially to characterize their linear optical performance throughout the year. Thus, the main purpose of this study is the development a test bench to experimentally, determine the thermal performance of a linear Fresnel concentrator. The collector used contains 14 rows of mirrors of 300 mm wide each, with a secondary concentrator with an opening of 300 mm, located 3 m high in relation to the plane containing the axes of the mirrors. Analyzes of existing methodologies and regulations were conducted to determine the performance of solar concentrators. Based on the existing standards, the test methodology and the necessary equipment to conduct the tests were defined. As a result of the tests, the collector efficiency curve and its performance parameters were obtained. The maximum efficiency approached 30% and maximum power reached was 6.25 kW. The optical analysis indicated the extremely high final losses on June 21, as only 30% of the absorber received the rays reflected by the mirrors.
Tue, 07 May 2019 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/89192019-05-07T00:00:00ZModelagem experimental e computacional DEM-CFD da fluidização de partículas Geldart-D com formato irregular
http://repositorio.jesuita.org.br/handle/UNISINOS/8918
Modelagem experimental e computacional DEM-CFD da fluidização de partículas Geldart-D com formato irregular
Silva, Álisson Renan Stochero da
Fluidized bed reactors find many applications in thermo-energy conversion processes. The preference for this type of system is due to the characteristics of high heat transfer and mass transfer rates between the particulate solid that composes the bed and the fluidizing agent. The three-dimensional computational simulation of these systems is able to provide local data such as velocity, pressure, temperature and chemical species concentration fields, which can not be obtained in zero-dimensional models or experimentally with the technology available today. Among the existing computational models, one of the most recent and attractive, due to its accuracy, is the one that uses the Discrete Element Method (DEM) and Computational Fluid Dynamics (CFD) coupling. In this approach, the motion of the granular phase is computed directly by the DEM, while the fluid is treated as a continuous medium by a CFD model. The interaction between the fluid and granular phases is performed by a coupling algorithm. With the objective of creating a DEM-CFD computational model for the fluidization of polypropylene particles, the physical characterization of the particulate material was carried out, determining the real and bulk mass densities, mean diameter, sphericity and repose and internal friction (drawdown) angles. The polypropylene particles were classified as of the Geldart-D type, and during their fluidization showed spout behavior. The particle-particle and particle-wall interaction coefficients, such as static friction, dynamic friction, restitution coefficient and rolling resistance, DEM input parameters were obtained through experiment planning and optimization technique. It was observed that among these parameters, what has the greatest effect on the results was the rolling resistance. Laboratory scale fluidizations provided reference values for minimum jet velocity, maximum bed pressure drop, and pressure drop in the minimum jet condition. During the simulations of the reactor, the refining of computational mesh was evaluated, as well as the refining of the wall. It was used four kinds of mesh, with the cells size based of particles diameters, for ranges of 2x, 3x and 5x, respectively. The DEM-CFD simulations of fluidization corroborate with the experimental results with an error of 1,88% to U_jm, 0,66% to 〖∆P〗_MÁX and 0,77% to 〖∆P〗_MÁX, being a powerful tool for studies of this species.
Fri, 12 Apr 2019 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/89182019-04-12T00:00:00ZAnálise termodinâmica, exergética e termoeconômica de um ciclo combinado com resfriamento do ar de entrada
http://repositorio.jesuita.org.br/handle/UNISINOS/8813
Análise termodinâmica, exergética e termoeconômica de um ciclo combinado com resfriamento do ar de entrada
Rodrigues, Fernando
In the last decades, thermoelectric power plants have been at highlights in the Brazilian energy sector due to the increase in energy demand and the search for greater reliability of the generation system, due to the increase of periods of Affluent Natural Energy (ANE) below Average of Long Term (MLT) in the southeast, region with the largest reservoirs in the country. Because it is a non-renewable energy, studies that provide a better performance in the use of thermal energy are required. In this way, this work proposes the analysis, through simulation in the EES (Engineering Equation Solver) software, of a thermoelectric combined cycle power plant with the use of two systems for the gas turbine inlet air cooling, being the evaporative cooling and the cooling by the mechanical steam compression method, to analyze the possible generation gains in two cities, Porto Alegre - RS and Mossoró - RN. The results show an improvement in the behavior of the plant in all aspects with the addition of cooling. Evaporative cooling provided an increase of 0.9% and 1.5% in annual average energy generation in Porto Alegre and Mossoró, and 0.5% and 0.8% exergetic efficiency, respectively. The unit cost of energy decreased from US$ 120.13 / MWh to US $ 114.88 / MWh in Porto Alegre and from US$ 121.17 / MWh to US$ 118.6 / MWh in Mossoró. The use of mechanical steam compression cooling resulted in an average increase in the annual power generation of 5.6% in Porto Alegre and 8.5% in Mossoró and 0.5% and a 0.6% increase in exergetic efficiency, in the same order. The unitary value of energy reached US$ 113.71 / MWh in Porto Alegre and US$ 117.08 / MWh in Mossoró.
Tue, 26 Mar 2019 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/88132019-03-26T00:00:00ZAnálise da variação dos parâmetros geométricos no desempenho de um refletor Fresnel Linear
http://repositorio.jesuita.org.br/handle/UNISINOS/8812
Análise da variação dos parâmetros geométricos no desempenho de um refletor Fresnel Linear
Webler, Luis Carlos
The objective of this work was to analyze the impact of the linear Fresnel reflector (LFR) parameters on its geometric efficiency and to define the width of the absorber according to the dispersion of the radiation reflected by the field of mirrors in the absorber input plane. The parameters analyzed were absorber height, mirror width, mirror spacing, radius of curvature for cylindrical curved mirrors and focal length for parabolic curved mirrors. The geometric efficiency was evaluated considering the energy in the form of solar radiation incident on the LFR during a day and the energy that effectively reached the absorber. In this analysis we also evaluated the losses present in the process, such as shading of the mirrors by the absorber, loss of radiation between mirrors, blocking between mirrors, cosine effect and losses by shading between mirrors. The methodology used for the analysis was the ray tracing, executed with a code developed in MATLAB. It was possible to conclude that the use of curved mirrors, with small rim angles, enables greater efficiency than with flat mirrors. The shape of the curvature, whether parabolic or cylindrical, did not affect the efficiency of the LFR. Spacing between mirrors must be the minimum that allows the movement of mirrors without the risk of interference. The increased height of the absorber also caused an improvement in the efficiency of the LFR. The parameters that minimize the width of the absorber, which was very important to minimize the losses by shading of the absorber on the field of mirrors, were determined. Other losses were also determined for each set of analyzed parameters. The results obtained can provide information for new projects.
Wed, 02 Jan 2019 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/88122019-01-02T00:00:00ZSimulação e análise de diferentes tecnologias de módulos fotovoltaicos aplicados em uma edificação residencial vertical
http://repositorio.jesuita.org.br/handle/UNISINOS/8762
Simulação e análise de diferentes tecnologias de módulos fotovoltaicos aplicados em uma edificação residencial vertical
Lauffer, Henrique de Araujo
Brazil faces a continuous increase in energy demand, and a major challenge for sustainable buildings is to reduce electricity consumption and at the same time supply its own energy demand with self-generation. Residential buildings account for 26% of national electricity consumption. It is necessary to seek new sources of energy to diversify and complement the electrical energy matrix. Photovoltaic solar energy integrated or applied in buildings is growing around the world and may be an interesting alternative to Brazil due to its modular features and available solar radiation. This work aims to analyze the energy behavior of a residential building with solar photovoltaic energy generation applied in the envelope and to compare the performance of different technologies of photovoltaic cells, building site, different orientations and evaluate the possibility of this generation to supply the typical consumption of a residential building. The simulations are performed using the EnergyPlus software for Porto Alegre/RS and Recife/PE. The building model is a typical residential building and has been defined from the current building pattern and the Brazilian statistical data. This study considers the application of photovoltaic generation on opaque surfaces of the building with monocrystalline silicon, multicrystalline, amorphous and also CIGS and CdTe technologies. The photovoltaic system has 1605 m² of installed module area and was divided into five sub-systems, to analyze the roof and the other four vertical façades orientation. For the city named Porto Alegre, all the technologies presented a sufficient production to supply the demand of the building electrical energy, but for Recife, only a-Si technology did not produce sufficient energy to supply the demand. The technology that presented the highest generation per unit area in Porto Alegre and Recife was monocrystalline silicon, with annual production of 140.7 kWh/m² and 146.6 kWh/m², respectively. From the generation results, relationships between generation by area in the coverage versus generation by area of vertical facade were created. For Porto Alegre, the vertical façades have very similar relations, except for the south façade, with the façade with better relation to the east with 1.73, followed by the north façades with 1.75, the west with 1.76, and the south façade presented a ratio of 3.30. In Recife, the best vertical facade for photovoltaic generation is the west façade, which presented a ratio of 1.39 times the area required to generate the same amount of electricity as the roof, followed by the east façades with a ratio of 2.20, north with 2.34 and finally the south façade with 2.69.
Fri, 22 Mar 2019 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/87622019-03-22T00:00:00ZDesign construtal de uma atleta em cada cavidade retangular contendo PCM
http://repositorio.jesuita.org.br/handle/UNISINOS/8660
Design construtal de uma atleta em cada cavidade retangular contendo PCM
Becker, Fábio
The use of thermal energy is an efficient form of energy storage and can be applied in various areas such as automotive industry, building industry, solar power plants and electronic components. Of the possible forms of thermal storage, latent heat is the most attractive, because it presents high energy storage capacity at constant temperature. Many studies focus on the use of Phase Change Material (PCM) as a form of energy storage. However, due to its low thermal conductivity, it is necessary to implement techniques of heat transfer enhancement. Among the possible existing techniques, the use of fins is the most widespread. Thus, it is important to analyze the best dimension of them, so that the process in which they are inserted, can be optimized. This work aims to verify the influence of the aspect ratio of a fin in a rectangular cavity, containing PCM lauric acid, in the process of melting. The results were obtained through numerical CFD simulation, using the finite volume method. The mathematical model is based on the equations of mass conservation, amount of movement and conservation of energy, being the phase change process based on the enthalpy-porosity model. The mathematical model was validated with experimental results from the literature and the computational meshes were verified by the GCI method. We simulated 09 fin aspect ratios and 09 fractions between cavity area and fin area, totalizing 78 configurations. With these results the Construtal Design method was applied to determine the optimum aspect ratio for each area fraction, which minimizes the total time of the PCM fusion process. In all the fractions of area analyzed, it was found that the larger the aspect ratio of the fin, the longer the total time of the fusion process. For the same value of aspect ratio, it was found that the larger the fraction of area, the smaller the total time of the process.
Wed, 27 Mar 2019 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/86602019-03-27T00:00:00ZSistema de rastreamento solar automático baseado em algoritmo de posição solar aplicado a um refletor fresnel linear
http://repositorio.jesuita.org.br/handle/UNISINOS/8659
Sistema de rastreamento solar automático baseado em algoritmo de posição solar aplicado a um refletor fresnel linear
Oliveira, Álvaro Daniel de
The use of solar energy can be a significant alternative to meet the growing demand for energy. In this context, solar concentrators have emerged as a very promising option. This research presents a model of automation of a solar tracker that dispenses the use of sensors to determine the position of the Sun. This determination is made only based on astronomical aspects, using an algorithm for calculating ephemeris, through which it is possible to predict the solar position by determining the values of the azimuth angles and solar elevation through time counting data constantly updated by a clock applied to the equation programmed in an Arduino module. For this, a comparison was made between two equation methods of apparent solar position, one of them based on Duffie and Beckman (2013) and the other based on Reda and Andreas (2008), the latter has the advantage of having a known uncertainty of 0.0003°, and the disadvantage of requiring a much more complex equation compared to the first method. Through simulations to obtain the required accuracy value that the tracking method should have to remain within the limits of the absorver area. It was verified that only the second method could provide the values within the required range of 0.2°. To confirm the applicability of the calculated values in the programming, it was simulate in the Tonatiuh software, in addition to measurements made directly on the mirrors, through a slope sensor with a resolution of 0.2°. The results obtained in the calculations were satisfactory, since they presented values very close to the simulated ones (maximum difference of 0,1º between both), whereas for the measured ones, the maximum difference for the calculated value was of 0.14º. After this confirmation, the values obtained in the programming have been applied in the positioning of a step motor responsible for the activation of a set of 14 mirrors coupled to each other and designed to concentrate the radiation in an absorber, using the technology of Fresnel Linear Reflector. This movement uses only one trigger, based on the observation that the values of the angular difference between the mirrors remain constant throughout the day.
Fri, 21 Dec 2018 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/86592018-12-21T00:00:00ZDesign construtal de aletas em cavidades resfriadas por fluidos não newtonianos
http://repositorio.jesuita.org.br/handle/UNISINOS/8651
Design construtal de aletas em cavidades resfriadas por fluidos não newtonianos
Bueno, Jocemar Felicio
Fri, 22 Feb 2019 00:00:00 GMThttp://repositorio.jesuita.org.br/handle/UNISINOS/86512019-02-22T00:00:00Z