Engenharia Mecânica
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/23
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4 resultados
Resultados da Pesquisa
- Exergy performance of human body under physical activities(2013) Mady C.E.K.; Albuquerque C.; Fernandes T.L.; Hernandez A.J.; Saldiva P.H.N.; Yanagihara J.I.; de Oliveira S.The aim of this work is to apply performance indicators for individuals under physical activity based on the concepts of exergy destroyed and exergy efficiency. The cardiopulmonary exercise test is one of the most used tests to assess the functional capacity of individuals with varying degrees of physical training. To perform the exergy analysis during the test, it is necessary to calculate heat and mass flow rates, associated with radiation, convection, vaporization and respiration, determined from the measurements and some relations found in the literature. The energy balance allowed the determination of the internal temperature over time and the exergy variation of the body along the experiment. Eventually, it was possible to calculate the destroyed exergy and the exergy efficiency from the exergy analysis. The exergy rates and flow rates are dependent of the exercise level and the body metabolism. The results show that the relation between the destroyed exergy and the metabolism is almost constant during the test, furthermore its value has a great dependence of the subject age. From the exergy analysis it was possible to divide the subjects according to their training level, for the same destroyed exergy, subjects with higher lactate threshold can perform more work. © 2013 Elsevier Ltd.
- Heat transfer and pressure drop correlations for finned plate ceramic heat exchangers(2015) Villanueva H.H.S.; de Mello P.E.B.© 2015 Elsevier Ltd.The 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 (Computational fluid dynamics) 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.
- Thermodynamic study of an EFGT (externally fired gas turbine) cycle with one detailed model for the ceramic heat exchanger(2012) De Mello P.E.B.; Monteiro D.B.The EFGT (externally fired gas turbine) cycle has been considered as an option to burn biomass in gas turbines. One key element on the implementation of one EFGT cycle is the high temperature heat exchanger (HTHE) necessary to support the high temperatures of operation. The performance of the HTHE, its effectiveness and pressure drop imposed to the gas flow, may have significant influence over the thermal efficiency of the EFGT cycle. The simulations of the EFGT cycle presented herein use correlations for the pressure drop and heat transfer of one ceramic heat exchanger of the plate and fin type, evaluated numerically. The results obtained show that the type of ceramic heat exchanger simulated presents adequate performance to be implemented in one EFGT cycle. © 2012 Elsevier Ltd.
- Thermal performance and pressure drop in a ceramic heat exchanger evaluated using CFD simulations(2012) Monteiro D.B.; de Mello P.E.B.There is one potential demand for heat exchangers capable of supporting high temperatures, typically higher than 800 °C, for use in thermal power plants. These heat exchangers could be used in the implementation of EFGT (Externally Fired Gas Turbines) cycles. To support these working conditions, during long periods of time, the heat exchanger should be constructed with adequate materials. Ceramics has been considered by many previous works as a choice. This work presents the results obtained with CFD simulations of one plate-fin ceramic heat exchanger. Correlations for the Colburn and friction factors, for a range of Reynolds number between 500 and 1500, are evaluated from the numerical results obtained with CFD. These correlations may be used for the thermal design of ceramic heat exchangers. One validation procedure is conducted comparing the simulation results with experimental data for a compact heat exchanger of similar configuration. © 2012 Elsevier Ltd.