Engenharia Mecânica

URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/23

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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.
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.
A study of a solar chimney to improve comfort inside shipping containers
(2014-06-15) MALTA, F. P.; GOUVEIA, J. L. F.; Cyro Albuquerque
Shipping 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.
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.
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%).
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.
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.
Biomechanical Analysis of Tissue Engineering Construct for Articular Cartilage Restoration—A Pre-clinical Study
(2022-04-15) FARIA, R. R. DE; MAIZATO, M. J. S.; CESTARI, I. A.; HERNANDEZ, A. J.; BUENO, D. F.; Roberto Bortolussi; Cyro Albuquerque; FERNANDES, T. L.
© 2022, Springer Nature Switzerland AG.The chondral lesion and osteoarthritis are conditions associated with an economic burden, since if left untreated may cause changes in the biomechanics of the joint and result in several injuries considered highly disabling to the individual. Mesenchymal Stem Cells (MSCs) have the immunomodulatory capacity and paracrine signaling that are useful for tissue bioengineering to treat bone and cartilage injuries. To the best of our knowledge, there is no institution in Brazil studying cartilage biomechanical properties in Good Manufacturing Practice (GMP) technique. Therefore, this study aims to describe biomechanics analysis for cartilage restoration by tissue engineering and cell therapy treatments in a GMP translational large animal model. A controlled experimental study in fourteen Brazilian miniature pigs was performed, using scaffold-free Tissue Engineering Construct (TEC) from dental pulp and synovial MSCs with 6 months follow-up. To compare the cartilage with and without TEC, indentation and maximum compressive tests were performed, as well as Finite Element model to simulate the osteochondral block and characterize its properties. The Young’s Modulus of each sample was determined, and the outcomes of maximum compressive test demonstrated the cartilage integrity. The proposed method was feasible and capable to properly evaluate articular cartilage restoration.
Tissue Engineering and Cell Therapy for Cartilage Repair: Preclinical Evaluation Methods
(2022-02-05) SANTANNA, J. P. C.; FARIA, R. R.; ASSAD, I. P.; PINHEIRO, C. C. G.; AIELLO, V. D.; Cyro Albuquerque; Roberto Bortolussi; CESTARI, I. A.; MAIZATO, M. J. S.; HERNANDEZ, A. J.; BUENO, D. F.; FERNANDES, T. L.
A chondral injury is a limiting disease that can affect the quality of life and be an economic burden due to the cost of immediate treatment and loss in work productivity. If left untreated, such an injury may progress to osteoarthritis, a degenerative and debilitating joint disease characterized by pain and functional impairment. Mesenchymal stromal cells (MSCs), which have immune-modulatory properties and the ability to differentiate into chondroblasts and osteoblasts, are a predictable source for the treatment of cartilage injuries. This article presents tools to evaluate cartilage restoration by tissue engineering and cell therapy treatment in a translational and preclinical large animal model. In this controlled experimental study with 14 miniature pigs, a scaffold-free tissue engineering construct (TEC) derived from dental pulp and synovial MSCs for cartilage therapy was tested. Total thickness cartilage defects were performed in both posterior knees. The defect was left empty in one of the knees, and the other received the TEC. The tissue repair was morphologically assessed by magnetic resonance imaging (MRI) using the three-dimensional double echo steady-state (3D-DESS) sequence, and compositional assessment was carried out based on the T2 mapping technique. The osteochondral specimens were fixed for histopathology, decalcified, subjected to standard histological processing, sectioned, and stained with hematoxylin and eosin. The sections stained for immunohistochemical detection of collagen types were digested with pepsin and chondroitinase and incubated with antibodies against them. The mechanical evaluation involved analysis of Young's modulus of the cartilage samples based on the indentation and maximum compression test. In addition, a finite element model was used to simulate and characterize properties of the osteochondral block. At 6 months after surgery, there were no complications with the animals and the MRI, histological, immunohistochemical, and biomechanical evaluations proved to be effective and qualified to differentiate good quality chondral repair from inadequate repair tissue. The proposed methods were feasible and capable to properly evaluate the defect filled with TEC containing stromal cells after 6 months of follow-up in a large animal model for articular cartilage restoration. Impact Statement Articular chondral injuries are prevalent and represent an economic burden due to the cost of treatment. The engineering of cartilage tissue can promote the repair of chondral injuries and is dependent on selecting appropriate cells and biocompatible frameworks. In this article, methods for evaluation of a scaffold-free cell delivery system made from mesenchymal stromal cells were present in a translational study that allows further clinical safety and efficacy trials.
Tissue Engineering and Cell Therapy for Cartilage Repair: Preclinical Evaluation Methods
(2022) SANTANNA, J. P. C.; FARIA, R. R.; ASSAD, I. P.; PINHEIRO, C. C. G.; AIELLO, V. D.; Cyro Albuquerque; Roberto Bortolussi; CESTARI, I. A.; MAIZATO, M. J. S.; HERNANDEZ, A. J.; BUENO, D. F.; FERNANDES. T. L.
A chondral injury is a limiting disease that can affect the quality of life and be an economic burden due to the cost of immediate treatment and loss in work productivity. If left untreated, such an injury may progress to osteoarthritis, a degenerative and debilitating joint disease characterized by pain and functional impairment. Mesenchymal stromal cells (MSCs), which have immune-modulatory properties and the ability to differentiate into chondroblasts and osteoblasts, are a predictable source for the treatment of cartilage injuries. This article presents tools to evaluate cartilage restoration by tissue engineering and cell therapy treatment in a translational and preclinical large animal model. In this controlled experimental study with 14 miniature pigs, a scaffold-free tissue engineering construct (TEC) derived from dental pulp and synovial MSCs for cartilage therapy was tested. Total thickness cartilage defects were performed in both posterior knees. The defect was left empty in one of the knees, and the other received the TEC. The tissue repair was morphologically assessed by magnetic resonance imaging (MRI) using the three-dimensional double echo steady-state (3D-DESS) sequence, and compositional assessment was carried out based on the T2 mapping technique. The osteochondral specimens were fixed for histopathology, decalcified, subjected to standard histological processing, sectioned, and stained with hematoxylin and eosin. The sections stained for immunohistochemical detection of collagen types were digested with pepsin and chondroitinase and incubated with antibodies against them. The mechanical evaluation involved analysis of Young's modulus of the cartilage samples based on the indentation and maximum compression test. In addition, a finite element model was used to simulate and characterize properties of the osteochondral block. At 6 months after surgery, there were no complications with the animals and the MRI, histological, immunohistochemical, and biomechanical evaluations proved to be effective and qualified to differentiate good quality chondral repair from inadequate repair tissue. The proposed methods were feasible and capable to properly evaluate the defect filled with TEC containing stromal cells after 6 months of follow-up in a large animal model for articular cartilage restoration. Impact Statement Articular chondral injuries are prevalent and represent an economic burden due to the cost of treatment. The engineering of cartilage tissue can promote the repair of chondral injuries and is dependent on selecting appropriate cells and biocompatible frameworks. In this article, methods for evaluation of a scaffold-free cell delivery system made from mesenchymal stromal cells were present in a translational study that allows further clinical safety and efficacy trials.

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