Engenharia Mecânica
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/23
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Resultados da Pesquisa
Artigo de evento 3 Citação(ões) na Scopus The effect of altitude and intensity of physical activity on the exergy efficiency of respiratory system(2013-07-16) HENRIQUES, I. B.; Carlos Mady; Cyro Albuquerque; YANAGIHARA, J. I.; OLIVEIRA JUNIOR, S.The effect of altitude on exercise performance of lowlanders has long been discussed, but it is still unclear whether the performance reduction is related to inefficiency of the respiratory system, tissues or both. In the present work, exergy analysis was applied to the human body in order to compare its exergy efficiency under basal conditions and during physical activity at sea level and high altitudes for different periods of acclimatization. Two control volumes were analyzed: the respiratory system, which comprises the lungs and the airways, and the human body as a whole. In the first control volume, the exergy rates and flow rates are associated with the venous blood and the inspired air in the inlet and the arterial blood and expired air in the outlet. An internal exergy variation due to the exergy metabolism of the lung, an exergy transfer rate associated with the metabolism of the lung and the power performed by the respiratory muscles were also taken into account. Analyzing the second control volume, the exergy transferred rate to the environment due to the heat losses by convection and radiation were considered, as well as the exergy flow rate associated with respiration and transpiration. The temperatures of different parts of the body and the heat losses to the environment were obtained from a heat transfer model of the human body. The data concerning gas and blood flows were obtained from a model of the respiratory system. The last one was modified based on medical literature to simulate the response to physical activity at high altitude for different periods of acclimatization, from the first moment that the body is exposed to a high altitude environment to three months of acclimatization. The results obtained indicated that the respiratory system exergy efficiency is reduced at high altitudes and under physical activity, while the exergy efficiency of the body increases for both parameters. Concerning the acclimatization period, its influence was more pronounced in the respiratory system. It was possible to observe a decrease in the exergy efficiency of the respiratory system in the first two days. From this moment on, the efficiency increased continuously until the twentieth day, when it is stabilized and remains constant.Artigo de evento 2 Citação(ões) na Scopus The effect of carbon monoxide in the exergy behavior of lungs(2017-07-02) CENZI, J. R.; HENRIQUES, I. B.; Cyro Albuquerque; YANAGIHARA, J. I.; OLIVEIRA, S.; Carlos Mady© 2017 IMEKOThe present work evaluates the impact of carbon monoxide inhalation in the human lungs exergy behaviour for different levels of intoxications and altitude. It is significant because this substance is one of the most common air pollutants in cities and an increasing in the destroyed exergy can be associated with a reduction in lifespan. Moreover, an evaluation of the severity as a function of the city height may intensify the hazard associated with carbon monoxide. In order to evaluate these consequences, a carbon monoxide transportation model obtained in literature was used to calculate the concentrations of oxygen, carbon monoxide and carbon dioxide in the different respiratory system tissues. With the purpose to better evaluate the different levels of carbon monoxide intoxication and hemoglobin concentration (which is a function of acclimatization time) it was proposed an exergy efficiency for the lungs. From this model, it was possible to conclude that a higher level of intoxication is associated to lower exergy efficiency values. Higher hemoglobin levels when associated to carbon monoxide intoxication also results in lower efficiencies.Artigo de evento 0 Citação(ões) na Scopus 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 0 Citação(ões) na Scopus Simulation of respiratory gas exchange in the placenta(2018-06-17) CENZI, J.; Cyro Albuquerque; Carlos Mady© 2018 University of Minho. All rights reserved.This work evaluates the gas exchange between a fetus circulatory system and the mother’s, which occurs in the placenta. Oxygen, carbon dioxide and carbon monoxide transport were analyzed. Carbon monoxide is one of the most common air pollutants in cities and it has a significant impact in physiological conditions even in low concentration. These effects are particularly prejudicial for pregnant women, fetus and newborn babies. A carbon monoxide transportation model, from literature, is adapted to simulate a pregnant woman. The respiratory gas exchange in the placenta is modeled, so it is possible to evaluate the concentration of the different gases. In this way, it is possible to assess carbon monoxide concentration in fetus and evaluate its effects. Exergy analysis are performed for both mother’s and fetus’ respiratory systems, in other to compare it to the respiratory system of a male adult. It is possible to verify that the fetus was more affected by CO poisoning than the adults, although it HbCO rate is significantly reduced compared to maternal’s.Artigo de evento 0 Citação(ões) na Scopus 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.- Comparison among exergy analysis methods applied to a human body thermal model(2022-01-15) RIBEIRO, T. J. D. S.; Carlos Mady© 2021 Elsevier LtdOver the past decades, thermodynamics concepts applied to biological systems, such as the human body, have aided in explaining their functioning. The first law of thermodynamics is primarily used — from the prime research that assessed the body surface area and the temperature distribution in members to the thermal comfort conditions with Fanger methods. The second law of thermodynamics may provide new insights to this discussion because it considers the internal irreversibilities of human metabolisms to the external communications with the environment. In this study, we compared three methods to evaluate the exergy behavior of the human body with an aim to determine the thermal comfort conditions. This is defined as 30oC and 50% of relative humidity. All methods indicated equivalent points of thermal comfort conditions, thus raising the question of how to apply the exergy analysis in similar reasoning for the three models. Therefore, a distinguishing feature of this study concerns the additional contributions when applying the exergy analysis in the same human thermal model. Furthermore, we attempted to compare and suggest connections or adjustments for each method to pave the way for the realization of a unified exergy model of the human body in the future.