Engenharia Mecânica
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/23
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Resultados da Pesquisa
Artigo de evento 0 Citação(ões) na Scopus 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 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.- The effect of carbon monoxide on the exergy behavior of the lungs(2018-12-05) CENZI, J. R.; Cyro Albuquerque; Carlos Mady© 2018 by the authors.The present work evaluates the impact of carbon monoxide (CO) inhalation on the human lung’s exergy behavior by considering different levels of intoxication and amounts of hemoglobin. Its impact is significant because CO is one of the most common air pollutants in cities and an increase in destroyed exergy may be correlated with lifespan reduction or the malfunctioning of certain human organs. An evaluation of the severity of intoxication as a function of city altitude may intensify the hazard associated with carbon monoxide. A computational model of human lungs obtained from the literature was used to calculate the concentrations of oxygen (O2), carbon monoxide (CO), and carbon dioxide (CO2) in the respiratory system. With the purpose of better evaluating the different levels of CO intoxication and hemoglobin concentration (which is a function of acclimatization time and some pathologies, such as anemia), a model calculating exergy efficiency for the lungs was proposed. From this model, it was possible to conclude that a higher level of intoxication is associated with lower exergy efficiency values. When associated with carbon monoxide intoxication, higher hemoglobin levels also result in lower efficiency. Eventually, a comparison between previous studies and the current study was carried out, regarding the method employed to calculate the exergy destroyed in the lungs, considering not only gas transport, but also hemoglobin concentration and its reaction with the gases from a second law perspective.
- Phenomenological and thermodynamic model of gas exchanges in the placenta during pregnancy: A case study of intoxication of carbon monoxide(2019-11-05) CENZI, J. R.; Cyro Albuquerque; MADY, C. E. K.© 2019 by the authors. Licensee MDPI, Basel, Switzerland.The present work simulates the transport of oxygen, carbon dioxide, and carbon monoxide between a fetus’s circulatory system and the mother’s. The organ responsible for this exchange is the placenta. Carbon monoxide is a common air pollutant, and it impacts the physiological conditions even in low concentration. The impacts of carbon monoxide are especially dangerous for pregnant women, fetuses, and newborn babies. A model of carbon monoxide transport, from the literature, is modified to simulate a pregnant woman (original model was a male), therefore changing some parameters to express the adjusted respiratory system. It was considered the gas exchange in the placenta, to evaluate the concentration of these different gases in the fetus arterial and venous blood. Three methods of the exergy analysis are implemented for both mother and fetus respiratory systems, aiming at the comparison with the respiratory system of a male adult. The destroyed exergy of the literature did not have the same trend as the models proposed in this article, taking into consideration the hemoglobin reactions. In contrast, the entropy generation associated only with the diffusion transport phenomena was one order of magnitude lower than the other methods. The placenta destroyed exergy rate is significantly higher compared to the irreversibilities of the mother’s respiratory system. One possible explanation is the fact that the placenta has other physiological functions than gas transportation.
- Exergy efficiency on incremental stationary bicycle test: A new indicator of exercise performance?(2019-12-01) MADY, C. E. K.; IGARASHI, T. L.; Cyro Albuquerque; SANTOS-SILVA, P. R.; FERNANDWS, A. J.; HERNANDEZ, A. J.© 2019, The Brazilian Society of Mechanical Sciences and Engineering.The first and second laws of the thermodynamics were applied to the human body to evaluate the performance of subjects under different training levels. Ten cyclists were evaluated in the stationary bicycle with the indirect calorimetry analysis to obtain the metabolism on an energy and exergy basis. A distinguishing feature of this article is the evaluation of the exergy efficiency of the body with the knowledge of the real performed power and the internal temperature (measured tympanic temperature and calculated esophagus temperature). Regarding the skin temperature, an infrared camera was used to measure different parts of the body. Therefore, the phenomenological behavior of the body was assessed and used as a basis to apply the exergy analysis. Results indicate that the destroyed exergy can be an indicator of performance when compared with maximum oxygen consumption. Nevertheless, more experiments must be carried out to proper state if there is a correlation. Eventually, the exergy efficiency was calculated for all subjects, and its value was around 23 to 28%.
- Exergy efficiency on incremental stationary bicycle test: A new indicator of exercise performance?(2019-11-16) MADY, CARLOS EDUARDO KEUTENEDJIAN; IGARASHI, TATIANE LIE; Cyro Albuquerque; SANTOS-SILVA, PAULO ROBERTO; FERNANDES, TIAGO LAZZARETTI; HERNANDEZ, ARNALDO JOSEThe frst and second laws of the thermodynamics were applied to the human body to evaluate the performance of subjects under diferent training levels. Ten cyclists were evaluated in the stationary bicycle with the indirect calorimetry analysis to obtain the metabolism on an energy and exergy basis. A distinguishing feature of this article is the evaluation of the exergy efciency of the body with the knowledge of the real performed power and the internal temperature (measured tympanic temperature and calculated esophagus temperature). Regarding the skin temperature, an infrared camera was used to measure diferent parts of the body. Therefore, the phenomenological behavior of the body was assessed and used as a basis to apply the exergy analysis. Results indicate that the destroyed exergy can be an indicator of performance when compared with maximum oxygen consumption. Nevertheless, more experiments must be carried out to proper state if there is a correlation. Eventually, the exergy efciency was calculated for all subjects, and its value was around 23 to 28%.
- Phenomenological and Thermodynamic Model of Gas Exchanges in the Placenta during Pregnancy: A Case Study of Intoxication of Carbon Monoxide(2019-10-19) CENZI, JULIANA RANGEL; Cyro Albuquerque; MADY, KEUTENEDJIAN CARLOS EDUARDOThe present work simulates the transport of oxygen, carbon dioxide, and carbon monoxide between a fetus’s circulatory system and the mother’s. The organ responsible for this exchange is the placenta. Carbon monoxide is a common air pollutant, and it impacts the physiological conditions even in low concentration. The impacts of carbon monoxide are especially dangerous for pregnant women, fetuses, and newborn babies. A model of carbon monoxide transport, from the literature, is modified to simulate a pregnant woman (original model was a male), therefore changing some parameters to express the adjusted respiratory system. It was considered the gas exchange in the placenta, to evaluate the concentration of these different gases in the fetus arterial and venous blood. Three methods of the exergy analysis are implemented for both mother and fetus respiratory systems, aiming at the comparison with the respiratory system of a male adult. The destroyed exergy of the literature did not have the same trend as the models proposed in this article, taking into consideration the hemoglobin reactions. In contrast, the entropy generation associated only with the diffusion transport phenomena was one order of magnitude lower than the other methods. The placenta destroyed exergy rate is significantly higher compared to the irreversibilities of the mother’s respiratory system. One possible explanation is the fact that the placenta has other physiological functions than gas transportation.