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Artigo de evento A novel scroll expander for flank leakage investigation: preliminary tests(2016-07-19) FANTI, G. R.; Gustavo Donato; Paulo de Mello© 2016 University of Ljubljana.The isentropic efficiency of the expander is a concern for organic Rankine cycle (ORC) and compressed air energy storage (CAES) implementation. In these applications, the expander alone has a great influence over the whole system efficiency. Scroll expanders are particularly interesting for the low power range comprehended between 1 and 10 kW. Many previous works have attributed to internal leakages a great importance to obtain high isentropic efficiency in these machines. We present herein experimental results obtained with a novel scroll expander constructed to investigate the effect of internal leakages. We discuss the geometry definition and design of the prototype in detail. The maximum mechanical power produced by the prototype was 923 W at 2690 rpm but its isentropic efficiency was only 30.6%. Filling factor as high as 4.9 reveals that internal leakage must be reduced to obtain a more efficient expander.Artigo de evento A study of a solar chimney to improve comfort inside shipping containers(2014-06-15) MALTA, F. P.; GOUVEIA, J. L. F.; Cyro AlbuquerqueShipping container is a cheap and easy way to build an internal environment. If occupied by people in warm climates, thermal discomfort usually occurs. The aim of this work is to investigate the use of solar chimney for natural ventilation inside containers. The cavity of the chimney, with trapezoidal cross section, is formed by placing a thermal insulating material against the lateral wall. The air enters the cavity from the internal environment through the bottom, flows to the top due to the heating of the metallic wall, and is dispersed in the external environment. An experimental apparatus was built with one cavity of a real container. The metallic wall was heated by electric heaters, in a range representative of solar incidence. Sensors of temperature and air velocity were positioned along the chimney. It was found that the chimney works even for low solar incidence. In the center between the metallic wall and the insulation, the air velocity is higher and the temperature is lower than near the walls. The effect of the radiative heat transfer from the metallic wall to the insulation significantly influences the temperature and the velocity profile.Artigo de evento Analysis of an absorption refrigeration system for air-conditioning of a microbus(2018-06-17) RANIERI, M. A.; MANIERI, G.; Carlos Mady; Cyro Albuquerque© 2018 University of Minho. All rights reserved.The present work evaluates the possibility of recovering cooling and exhaust systems energy of an internal combustion engine as an energy source input for an absorption refrigeration cycle. From experimental data of the cooling and exhaust systems of an urban microbus under various loading and rotation conditions, simulations of a lithium bromide absorption cycle were performed. The performance of the absorption cycle was obtained in each condition of use of the vehicle: warm-up, city and road route. The results showed that the cooling capacity was 0.97 kW during the initial phase of warming-up, reaching 7.01 kW in road route. In the city condition, which is the main application of the micro-bus studied, 4.17 kW of cooling capacity was found, which represents 78.9% of the cooling capacity in vehicles of this category.Artigo de evento Another argument to consider the reliability of the uncertainty Type B similar to Type A(2006-09-22) BULBA, E. A.; SVOLL, V. R.The ISO-GUM express that the standard deviation of the experimental standard deviation of the mean q obtained for ratio σ[s(q)]/ σ (q) has a not negligible value for practical values of n, and therefore that Type A evaluations of the standard uncertainty are not necessarily more reliable than Type B evaluations. Although this correct comparison either, the assertion based on the value of the s(q) is the not best, in way that this work to consider other relation as argument for this comparison.Artigo de evento Assessment of Different More Electric and Hybrid-Electric Configurations for Long-Range Multi-Engine Aircraft(2021-06-28) GIMENEZ, F. R.; Carlos Mady; HENRIQUES, I. B.© ECOS 2021 - 34th International Conference on Efficency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems.This work intends to assess the characteristics, penalties, gains, and challenges through the Electrification and Hybridization process for long-range aircraft. A system, engines and mission level analysis was created focusing on a Thermodynamics and financial approach. A conventional reference aircraft was compared with enhanced more electric and hybrid-electric versions of itself. These new models may carry batteries, which supply the aircraft systems and/or engines, or not. State-of-the-art propulsion and systems’ architecture were also implemented within the cutting-edge airplanes. A full factorial analysis was conducted to vary the batteries’ energy density and the hybridization ratio for the hybrid configurations. A typical mission profile was developed to match the boundary conditions in all cases. Hybrid powertrains confirmed superior behavior than any other cases. The least efficient hybrid configuration, with intermediate battery choices, reduced 10.7% the fuel consumption upon the conventional aircraft and 1.0% facing the battery powered more electric option. Moreover, both baseline models were also surpassed by the worst midway-battery hybrid airplane by 3.6% and 1.0% in overall mission exergy efficiency. Notwithstanding the markets’ actual low battery density, long-range hybrid-electric aircraft will take substantial time to become viable. Nevertheless, only after a significant period, the use of hybrid-electric aircraft will be economically feasible. In the end, preliminary well-to-wake CO2 emissions analysis was developed in all cases for different electricity mix scenarios to observe the environmental impact and viability of the conventional and state-of-the-art configurations.Artigo de evento CFD simulation of scroll expanders: Influence of pressure ratio and flank clearance over the performance(2019-06-23) OLIVEIRA, F. V.; SILVA, F. M. F.; Paulo de Mello© ECOS 2019 - Proceedings of the 32nd International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems. All rights reserved.Scroll expanders are considered ideal for low power applications, in particular in small scale ORC (organic Rankine cycle). Internal leakages decrease considerably the isentropic efficiency of scroll expanders and consist the main source of inefficiency. In this paper, the performance of one scroll expander working with air for which experimental data is available is simulated. The influence of pressure ratio and tangential clearance over the results is investigated. Transient 2D CFD (computational fluid dynamics) simulations of the compressible flow capable of quantifying the internal leakages present in this machine were performed. The filling factor, generated power and isentropic efficiency were obtained and compared with experimental results from our research group. The results obtained reveal that the pressure ratio variation does not change the filling factor, thereby the internal leakages remain practically constants with the inlet pressure increase. The pressure ratio value for which the highest isentropic efficiency is obtained tends to reduce when increasing the internal leakages. The CFD simulations have shown generated power 11% higher if compared with experimental results. This difference can be attributed to uncertainty in tangential clearance measurements, radial leakage and pressure drop at expander inlet not considered in the 2D simulations.Artigo de evento Charge-based continuous equations for the transconductance and output conductance of graded-channel SOl MOSFET's(2007-01-05) Michelly De Souza; Marcelo Antonio PavanelloThis paper presents charge-based continuous equations for the transconductance and output conductance of submicrometer Graded-Channel (GC) Silicon-On-Insulator (SOI) nMOSFET. The effects of carrier velocity saturation, channel length modulation and drain-induced barrier lowering were taken into account in the proposed equations. Experimental results were used to test the validity of the equations by comparing not only the transconductance and the output conductance, but also the Early voltage and the open-loop voltage gain, showing a good agreement in a wide range of bias.Artigo de evento Design of a hydraulic turbine control system by numerical optimization(2015-09-21) CANONICO, R.; Renato Aguiar; Fabrizio Leonardi© 2015 Dime universita di genova, dimeg university of calabria. All rights reserved.This work proposes the use of numerical optimization based on Direct Transcription as a method for the design of the control system for hydroelectric turbines. The control design for this application involves constraints but the usual control techniques do not allow explicitly to incorporate constraints in its formulation or are very sensitive to initial estimates of the optimization problem implying in convergence issues. The Direct Transcription is an alternative optimization-based design where the dynamics are discretized and included as constraints of the optimization problem causing the errors due to the quality of the initial estimate to be diluted over the discretization nodes. The constraints considered are related to the actuator and other operating limits during a change maneuver of operating point.Artigo de evento Effects of crack tunneling on the elastic unloading compliance of C(T), Se(B) and clamped SE(T) specimens(2017-06-18) Gustavo Donato; ANDRADE, L. G. F.© 2017 Chinese Society of Theoretical and Applied Mechanics. All Rights Reserved.This paper investigates how crack front curvature affects instantaneous crack size predictions based on the elastic unloading compliance technique applicable to SE(B), C(T) and clamped SE(T) specimens. Relative crack depths (a/W) of 0.2, 0.5 and 0.7, alongside five levels of crack curvature were considered. Crack front was modeled as a semi-ellipse. It was shown that for the same ASTM equivalent straight crack [1] compliance decreases as tunneling increases. Since the maximum crack curvature allowed by ASTM is very restrictive, compliance did not change much within that limit, but if violated, a remarkable deviation may occur. As a step to improve such techniques, a new formulation to determine the equivalent straight crack was developed. The new proposal shows reduced errors on compliance as crack curvature grows when compared to current ASTM proposal.Artigo de evento Effects of plasticity on the elastic unloading compliance of C(T), Se(B) and clamped SE(T) specimens(2017-06-18) Gustavo Donato; ANDRADE, L. G. F.© 2017 Chinese Society of Theoretical and Applied Mechanics. All Rights Reserved.This paper investigates how plasticity affects instantaneous crack size predictions based on the elastic unloading compliance technique applicable to SE(B), C(T) and clamped SE(T) fracture mechanics specimens. Since this method assumes linear-elastic constitutive model, plasticity ahead of the crack may alter crack-size predictions due to residual stresses, local deformations, among other reasons. In order to better understand such effects and develop corrections, three materials were modeled with different hardening and same elastic modulus to represent modern high strength steels. Specimens were loaded, unloaded and reloaded considering large geometry change for varying CMOD values in order to induce varying levels of plasticity. Results show that for all specimens, specially for clamped SE(T), compliance will increase for larger CMOD values, showing that plasticity may affect crack size predictions and deserve further attention. A trend was found for the three geometries under investigation, being SE(T) the most affected.Artigo de evento Efficiency trade-offs in the Brazilian passenger vehicle fleet(2021-06-28) MOSQUIM, R. F.; Carlos Mady© ECOS 2021 - 34th International Conference on Efficency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems.Transportation energy demand in Brazil increases despite vehicles improving technologically. Models calculating possible avoided emissions can benefit from the estimation between vehicle attribute trade-offs and technological progress. A regression analysis with year-fixed effects was carried for 1,656 models in the passenger vehicle fleet in Brazil from 2004 to 2020. Weight and aerodynamic drag had the main effect on fuel economy. Parameters related to power, such as displacement, horsepower, torque and acceleration, impacted as well. Hybrids had positive effects, but its diffusion in Brazil is likely to be slow. Fuel economy could have been 20.9% to 23.4% higher in the period if all technological progress were expended on better fuel economy, as opposed to the 12.1% actually realized. This gap is an important aspect that should not be neglected in scenario-building.Artigo de evento Exergy analysis as a tool for the rational use of energy in an average house and everyday personal habits(2021-06-28) PEREIRA, M. T. R. M.; Carlos Mady© ECOS 2021 - 34th International Conference on Efficency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems.This article focuses on studying the exergy efficiency of an average household as an appropriate guideline for decision-making concerning technologies and habits in the context of the Brazilian energy matrix and other economic sectors. The exergy behavior is evaluated as a function of the household’s electric appliances and the need for essential services and consumption of everyday items, e.g., food and water. The methods involve evaluating the inputs and outputs to a control volume surrounding the house. As inputs, food, electricity, and fuels were considered, whereas outputs include discharges to the environment in the form of sewage and liquids and urban solid residues. The results show an overall exergy efficiency of 15% for the household, and that the demand for transportation is the most relevant hotspot in both exergy and environmental terms.Artigo de evento Exergy analysis of the body efficiency during aerobic activities(2018-06-17) IGARASHI, T. L.; SPANGHERO, G. M.; FERNANDES, T. L.; HERNANDEZ, A. J.; Carlos Mady; Cyro Albuquerque© 2018 University of Minho. All rights reserved.The First and Second Law of Thermodynamic were applied to the human body in order to evaluate the quality of the energy conversion process during muscle activity. Such an implementation represents an important issue in the exergy analysis of the body, because there is a difficulty in literature to evaluate the performed power in some activities. To this aim, the exergy analysis was applied to an aerobic activity (treadmill running test) to evaluate the efficiency of energy conversion process in the body and cells. Physiological and test data such as, oxygen consumption, carbon dioxide production, skin temperature, treadmill velocity, air temperature, relative humidity, were measured. Different methods to calculate the performed power were studied and the results compared with the First Law of Thermodynamics concerning to evaluate the accuracy of equations. From the Second Law of Thermodynamics point of view it was obtained similar, yet complementary results. Some methods resulted in efficiency around 10% others close to the maximum possible performed work, which is the exergy released in ATP hydrolysis (around 50 to 60%).Artigo de evento Exergy analysis of the human respiration under physical activity(2009-08-30) Cyro Albuquerque; PELLEGRINI, L. F.; FERREIRA, M. S.; YANAGIHARA, J. I.; OLIVEIRA, S. DE.© 2009 by ABCM.This paper presents an exergy analysis of the human body under physical activity. A model of the respiratory system and a model of the thermal system were used for this purpose. They consider heat and mass transfers in lungs, tissues and blood. Each component of those models is represented by an uniform compartment governed by equations for diffusion, convection, O2 consumption, CO2/heat generation and heat and mass transfer with the environment. The models allow the calculation of the exergy destruction in the lung and tissues, and the participation of each entropy generation mechanism in the total generation. Furthermore, a discussion is proposed regarding the efficiency of the human body under physical exercise.Artigo de evento Heat transfer and pressure drop correlations for finned plate ceramic heat exchangers(2014-06-15) VILLANUEVA, H. H. S.; Paulo de MelloThe use of ceramic materials is a good option to build heat exchangers for high temperature applications when cost is a concern. This work presents heat transfer and pressure drop correlations for one finned plate heat exchanger evaluated using CFD simulations. One adequate turbulence model was used to include transitional Reynolds number range. The influence of geometrical parameters is included into the correlations, following the same approach commonly used for offset strip fins heat exchangers. For validation purposes, the CFD results are compared to experiments for one particular geometrical configuration. The resultant correlations for the high temperature heat exchanger could be used for optimization purposes, considering possible applications. Analysis of simulation results revealed significant heat transfer enhancement produced by a horseshoe vortex formed in the frontal part of the fins.Artigo de evento Incremental root locus and pid tuning(2006-10-04) GOMES, S. C. P.; Fabrizio Leonardi; DA CRUZ, J. J.This work discusses the Incremental Root Locus property and one application of it to PID controllers tuning. It is shown that using that property it is easy do determine the departure angle from the real axis, which is a not a trivial task using the classical root locus rules. As an application, a procedure for tuning PID controllers in two steps is shown. Firstly it is necessary to perform a step response test using a proportional controller in order to stabilize the system. In a second step the PID design is performed by a zero-pole canceling. The controller obtained is a two-degree-of-freedom PID controller. Simulations carried out indicate that the controller associated with the setpoint tracking exhibits an almost first-order response whereas the one associated with the disturbance rejection exhibits a more oscillatory response. As illustrations, a real application for a position servo control system and some design projects tested by simulation were done.Artigo de evento Integrated manufacturing laboratory and software tools applied to an industrial engineering undergraduate course(2009-03-23) Fabio Lima; PRADO, A. C.; Alexandre Augusto Massote; Fabrizio LeonardiThis paper describes the experience of using software tools associated with an integrated manufacturing laboratory in an industrial engineering undergraduate course at FEI (Fundacao Educacional Inaciana, Brazil). The integrated manufacturing laboratory has got three complete manufacturing cells integrated by computer. The aim of the laboratory is to provide to the industrial engineering student a powerful analysis capability of how to use these kinds of systems to improve product quality and production performance. To do that, computational models are implemented using software tools like Visual Object Net++, Promodel® and WEB support. Finally, the models are validated in laboratory experiments. It was observed that such strategy has been given excellent learning results.Artigo de evento Investigation of residual stress in laser welding dissimilar materials Investigação da tensão residual na soldagem laser de mate riais dissimilares(2010-07-26) MIRIM, D. DE C.; BERRETTA, J. R.; ROSSI, W. DE; LIMA, N. B. DE; OLIVEIRA, R. R. DE; Sergio Delijaicov; GOMES, D. O.One of the most critical problems found in the different materials welding is the residual stress formation, that happens mainly for the fact of those materials they possess coefficients of thermal expansion and different thermal conductivities. Like this in this work the residual tension was evaluated in the technique of welding laser among the steel low carbon, AISI 1010 and AISI 304. The materials were united for it welds autogenous of top with a laser of continuous Nd:YAG in that they were varied the potency, speed and the focus of the laser stayed constant in relation to surface of the sample. The main objective of the study went identification and to analysis of the residual stress in HAZ on both sides of seem. Um planning factorial of two factors at two levels each it was executed for optimization the combination of the factors potency and speed. The obtained answers were the residual stress in different depths in HAZ. In the surface of the sample measures of residual stress were accomplished by the technique of X-ray difraction. The hole drilling strain gage method it was applied to measure the residual stress on both sides of the union. The results were analyzed using the variance analysis and the statistical regression based on the different influences of the entrance and combination of the factors in the residual stress generated in that union. The results indicate that the development of models can foresee the answers satisfactorily.Artigo de evento Is there a third abrasive wear mode?(2013-09-08) Ronaldo Câmara Cozza; SCHON, C. G.Artigo de evento Modeling heat transfer in human arm and forearm: Effect of countercurrent heat exchange and superficial veins(2009-06-25) FERREIRA, M. S.; YANAGIHARA, J. I.