Navegando por Autor "Brum, Ruth da Silva"

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An experimental study on the use of earth-air heat exchangers (EAHE)
(2014) Vaz, Joaquim; Sattler, Miguel Aloysio; Brum, Ruth da Silva; Santos, Elizaldo Domingues dos; Isoldi, Liércio André
The thermal potential of Earth-Air Heat Exchangers (EAHE) is experimentally investigated for a placementin Viamão, city located in the south of Brazil. Three independent ducts are buried in the soil, ducts A and B are installed at a depth of 1.60 m and 0.60 m apart, while duct C is installed at a depth of 0.50 m. Thethermal conditions of one build named Casa Ventura are improved with the EAHE. The temperatures forthe soil, external air and in buried ducts in several positions are acquired along one year (2007). The mainpurpose here is the achievement of the transient behavior of temperature fields for the external air, soiland buried ducts and the best periods of time for employment of device. Results showed that the monthsof May and February were the best for heating and cooling the air used in Casa Ventura, respectively.Moreover, it was developed a complete database about the transient temperatures of the soil, externalair and inside the building.
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A matlab code to fit periodic data
(2015) Brum, Ruth da Silva; Ramalho, Jairo Valões de Alencar; Rocha, Luiz Alberto Oliveira; Isoldi, Liércio André; Santos, Elizaldo Domingues dos
This paper presents a computer method to find the best sine-based function, in the sense of least squares, to fit periodic data. Even though the least squares method is not a novelty, there is a void in the literature about its use to find trigonometric functions, particularly when it gives rise to nonlinear systems, as it is done in this article. The respective code, implemented in the Matlab programming language, is detailed and analyzed exploring experimental data from the air and soil temperatures measured along the year in earth air heat exchangers (EAHE) built in the facilities of a case study house in the Brazilian state of Rio Grande do Sul. The fitting curves have been employed by the authors in different works to define boundary conditions to study new computer models of EAHE.
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Modelagem computacional de trocadores de calor solo-ar
(2013) Brum, Ruth da Silva; Isoldi, Liércio André
Atualmente, há um foco na busca por fontes de energia renováveis, bem como alternativas para racionalizar o uso de energia elétrica. Neste sentido, o emprego dos Trocadores de Calor Solo-Ar (TCSA) se destaca devido ao seu baixo consumo de energia. Basicamente, TCSA são sistemas nos quais o ar ambiente ´e aquecido ou resfriado através da sua circulação em dutos enterrados. Isto ocorre pela inércia térmica do solo, de modo que no verão este é mais frio que o ar externo, ocorrendo o contrário no inverno. Nesta disserta¸c˜ao, foram feitas avaliações num´ericas do potencial térmico do solo para a aplica¸c˜ao em projetos de TCSA, usando modelos computacionais em duas e três dimensões. Deve-se destacar que este trabalho contribuiu com a an´alise de novos modelos computacionais de TCSA, sendo um bidimensional e dois tridimensionais, cujo tempo de processamento foi inferior a 50% de outros modelos encontrados na literatura. Um estudo de caso foi desenvolvido onde a influência da profundidade de instalação no potencial térmico dos TCSA foi investigada. As simulações foram realizadas utilizando o software FLUENT que baseia suas aproximações no método de volumes finitos. O escoamento turbulento no duto foi abordado com o modelo das tensões de Reynolds. Os resultados do comportamento térmico do solo apresentaram uma excelente concordância com soluções analíıticas mostrando a validade e eficiência dos modelos computacionais. Os resultados numéricos dos modelos do solo também foram confrontados com os experimentais previstos na literatura e mostraram uma concordância qualitativamente satisfatória. A partir dos resultados numéricos obtidos, foi possíıvel avaliar o comportamento anual do campo de temperatura no solo e no interior do duto. No estudo de caso constatou-se que o potencial de resfriamento e aquecimento do ar aumenta com a profundidade de instalação dos dutos. Porém, a partir de 3m de profundidade, a temperatura de saída do ar teve um comportamento com pouca variação, não havendo ganho significativo em fazer escavações mais profundos. Para o resfriamento do ar, em particular, os resultados apontam que até mesmo dutos enterrados a pequenas profundidades podem ser eficazes.
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A new computational modeling to predict the behavior of Earth-Air Heat Exchangers
(2013) Brum, Ruth da Silva; Vaz, Joaquim; Rocha, Luiz Alberto Oliveira; Santos, Elizaldo Domingues dos; Isoldi, Liércio André
The use of renewable energy sources to improve the thermal conditions of built environments and hencedecreasing the consumption of conventional energy is an important aspect to design a sustainable build-ing. Within this context, it is possible to harness the solar energy that reaches the Earth’s surface andis stored by the soil as thermal energy. To do so, the Earth-Air Heat Exchanger (EAHE) device can beemployed, consisting of a buried duct through which the external ambient air is insufflated. The flowingair exchanges heat with surround soil, and leaves the device with a milder temperature compared to itsinput temperature. The main goal of this work was to present a new computational modeling to predictthe thermal behavior of EAHE. This new numerical model has the advantage of needing a lower com-putational effort, allowing the study about the influence of operational and constructive parameters, aswell as, the application of geometric optimization methods in EAHE. A case study was developed whereinfluence of the installation depth in the thermal potential of an EAHE was investigated. The results arein agreement with those found in literature; however they were obtained with a reduction in processingtime of almost 45%.
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Numerical investigation about the improvement of the thermal potential of an Earth-Air Heat exchanger (EAHE) employing the Constructal Design method
(2015) Rodrigues, Michel Kepes; Brum, Ruth da Silva; Vaz, Joaquim; Rocha, Luiz Alberto Oliveira; Santos, Elizaldo Domingues dos; Isoldi, Liércio André
The Earth-Air Heat Exchanger (EAHE) is a device used to improve the thermal condition of built environments, allowing the reduction of electrical energy consumption of traditional air conditioner systems. Fundamentally, its operational principle is based on fluid mechanics and heat transfer, areas in which Constructal Design has been widely used to seek for the optimal geometries, i.e., which leads to the best performances. In spite of this fact, the employment of Constructal Design for improvement of the EAHE thermal potential has not been performed into literature. Therefore, the main purpose of this work is to perform a numerical investigation on different geometrical configurations of an EAHE using the Constructal Design to obtain the highest thermal potential. Results indicated that, for the same area occupied by the ducts and fixed mass flow rate of air, the increase of the number of ducts (complexity of geometry) improved the EAHE thermal performance up to approximately 73% for cooling and 115% for heating.
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Two-dimensional computational modeling of the soil thermal behavior due to the incidence of solar radiation
(2013) Brum, Ruth da Silva; Isoldi, Liércio André; Santos, Elizaldo Domingues dos; Vaz, Joaquim; Rocha, Luiz Alberto Oliveira
Nowadays, there is a focus on finding sustainable energy sources, as well as, alternatives to rationalize the use of electrical energy. In this sense, the employment of Earth-Air Heat Exchangers (EAHE) is one technique which allows the reduction of energy consumption for climatization of buildings environments. The present study shows the evaluation of a numerical method to estimate the ground thermal potential, allowing its applicability for future thermal design of EAHE. The soil domain is considered two-dimensional and a transient solution for the thermal behavior of the soil is obtained. Moreover, a soil surface temperature distribution equation based on experimental data is employed to define the domain boundary conditions. The simulations are performed with a numerical method based on the finite volume method, more precisely using the software FLUENT®. The results presented an excellent agreement with analytical solutions showing the validity and effectiveness of the computational model for prediction of the soil behavior. The numerical results were also confronted with experimental ones predicted into literature and show a good agreement, with a deviation lower than 14%. The main difference is attributed to the duct presence which is taken into account only for the experimental study.