Engenharia Mecânica
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/23
Navegar
3 resultados
Resultados da Pesquisa
- Could an absorption refrigeration system be driven by the engine exhaust gas and cooling fluid of a minibus?(2021-12-05) RANIERI, M. A.; MANIERI, G.; MADY, C. E. K.; Cyro Albuquerque© 2021, The Brazilian Society of Mechanical Sciences and Engineering.This study evaluates the possibility of recovering energy from the cooling and exhaust systems of an internal combustion engine as a source input for an absorption refrigeration system. Sensors were installed in a minibus to measure the temperature and mass flow of the exhaust gas. Their signals, together with those of the vehicle’s built-in sensors, were acquired during tests under different conditions: warm-up, city route, and highway route. Simulations of a lithium bromide absorption refrigeration cycle were performed using the experimental data as input. In the model, a fraction of the engine cooling fluid and exhaust gas was considered as the generator’s energy source. Hence, recuperative heat exchangers were included with an auxiliary water circuit between the generator and exhaust system. The results showed an average cooling capacity of 1.5 kW during the initial warm-up phase, reaching 7.2 kW under road-route driving conditions. In the city, where minibusses are used most, a cooling capacity of 3.6 kW was found, that is, 68% of the cooling demand in vehicles in this category. To operate under these conditions and during the warm-up period, an alternative system would have to be added as an electrical heater. Moreover, the system requires a controller to bypass a fraction of the available exhaust gas during high engine demands.
- 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%.