Engenharia Mecânica
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/23
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2 resultados
Resultados da Pesquisa
- Numerical study on heat transfer performance of geothermal piles in a Brazilian sandy soil(2022-03-05) DE ALMEIRA, C. R.; Cyro Albuquerque; TSUHA, C. H. C.; BOSCOV, M. E. G.© 2022, Associacao Brasileira de Mecanica dos Solos. All rights reserved.The worldwide consumption of electric energy destined for air conditioners, expected to triple by 2050, can be lessened by geothermal piles, which transfer heat from the internal environment of buildings to the subsoil. This paper shows the influence of pile geometry and properties of soil, pile, and pipe materials on the heat transfer of a geothermal pile to the surrounding soil, to support design from the viewpoint of thermal performance optimization. A numerical model was developed with ANSYS CFX 19.2, a high-performance Computational Fluid Dynamics tool, and calibrated using data from a thermal response test performed in a saturated sandy soil in São Paulo, Brazil. A parametric analysis was carried out varying pile length, diameter, and slenderness; soil and pile material conductivities; degree of saturation; fluid inlet temperature; fluid flow rate; and pipe thermal resistance. Results show that the fluid inlet temperature is the most influential parameter on the thermal performance of the pile. Heat transfer grows when geometrical parameters (diameter and length) are increased mainly due to an increase in heat exchange surface area, whereas the normalized heat transfer rate per unit of surface area of the pile is practically unaltered. Higher soil, pipe and pile thermal conductivities improve thermal performance. The degree of saturation increases the thermal conductivity of the soil; however, the effect is not remarkable on the system’s thermal performance for saturation degrees higher than 20%. The fluid flow must be turbulent but increases above a certain flow rate do not improve the thermal performance.
- 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.