Navegando por Autor "Link, Fernanda Bichet"

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Constructal design of a x-shaped cavity cooled by convection
(2014) Link, Fernanda Bichet; Rocha, Luiz Alberto Oliveira; Santos, Elizaldo Domingues dos; Isoldi, Liércio André
This paper applies Constructal design to study the geometry of a X-shaped cavity that penetrates into a solid conductive wall. The objective is minimizing the dimensionless maximal excess of temperature between the solid body and the cavity. There is uniform heat generation on the solid body. The cavity surfaces are cooled by convection heat transfer while the solid body is subjected to adiabatic conditions on its outer surfaces. The total volume and the cavity volume are fixed, but the lengths and thickness of the X-shaped cavity can vary. The emerged optimal configurations and performance are reported. The effect of the area fraction φ which denotes the ratio between the cavity area and the total area of the geometry, and the ratio between the length and thickness of the branch cavity, H1/L1, on the dimensionless maximal excess of temperature is numerically investigated. The results show that the dimensionless maximal excess of temperature θmax,min decreases approximately 60% when the cavity fraction increases from φ = 0.05 to 0.25. The results also show that the X-shaped cavity performs approximately 45% better when compared to a C-shaped cavity under the same thermal conditions. The optimal X-shaped cavity is also in accordance with the optimal distribution of imperfections principle.
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Constructal design of isothermal x-shaped cavities
(2014) Lorenzini, Giulio; Biserni, Cesare; Link, Fernanda Bichet; Santos, Elizaldo Domingues dos; Isoldi, Liércio André; Rocha, Luiz Alberto Oliveira
This paper applies constructal design to study the geometry of a X-shaped cavity that penetrates into a solid conducting wall. The objective is to minimize the maximal dimensionless excess of temperature between the solid body and the cavity. There is uniform heat generation on the solid body. The total volume and the cavity volume are fixed, but the geometric lengths and thickness of the X-shaped cavity can vary. The cavity surfaces are isothermal while the solid body has adiabatic conditions on the outer surface. The emerged optimal configurations and performance are reported graphically. When compared to the Y- and C- and H-, the X-shaped cavity performs approximately 53% better than the Y-shaped cavity and 68% better than the C-shaped cavity for the area fraction φ = 0.05, while its performance is 22% inferior to the performance of the H-shaped cavity for the area fraction φ = 0.1. The results indicate that the increase of the complexity of the cavity geometry can facilitate the access of heat currents and improve the performance of the cavities.
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Constructal design of non-uniform x-shaped cavity
(2013) Link, Fernanda Bichet; Santos, Elizaldo Domingues dos; Isoldi, Liércio André; Rocha, Luiz Alberto de Oliveira
This paper applies constructal design to study a non-uniform X-shaped cavity that penetrates a conductive solid wall. The goal is to minimize the maximal dimensionless excess of temperature between the solid body and cavity. There is a uniform heat generation on the solid body. The total volume and the volume of the cavity are fixed, but the angle formed between the stems of the cavity may vary. The cavity surfaces are isothermal while the solid body has adiabatic conditions in the outer surface. Results indicate that the optimal X-cavity performs 60.1% better than the Cshaped cavity and 44% better than the T-shaped cavity. However, it has a performance approximately 38% inferior than the performance of the optimized H-shaped cavity.
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Constructal design of T-shaped cavity for several convective fluxes imposed at the cavity surfaces
(2013) Lorenzini, Giulio; Biserni, Cesare; Link, Fernanda Bichet; Isoldi, Liércio André; Santos, Elizaldo Domingues dos; Rocha, Luiz Alberto Oliveira
The purpose here is to investigate, by means of the constructal principle, the influence of the convective heat transfer flux at the cavity surfaces over the optimal geometry of a T-shaped cavity that intrudes into a solid conducting wall. The cavity is cooled by a steady stream of convection while the solid generates heat uniformly and it is insulated on the external perimeter. The convective heat flux is imposed as a boundary condition of the cavity surfaces and the geometric optimization is achieved for several values of parameter a = (2hA1/2/k)1/2. The structure of the T-shaped cavity has four degrees of freedom: L0/L1 (ratio between the lengths of the stem and bifurcated branches), H1/L1 (ratio between the thickness and length of the bifurcated branches), H0/L0 (ratio between the thickness and length of the stem), and H/L (ratio between the height and length of the conducting solid wall) and one restriction, the ratio between the cavity volume and solid volume (φ). The purpose of the numerical investigation is to minimize the maximal dimensionless excess of temperature between the solid and the cavity. The simulations were performed for fixed values of H/L = 1.0 and φ = 0.1. Even for the first and second levels of optimization, (L1/L0) ○○ and (H0/L0)○, the results revealed that there is no universal shape that optimizes the cavity geometry for every imposed value of a. The T-shaped cavity geometry adapts to the variation of the convective heat flux imposed at the cavity surfaces, i.e., the system flows and morphs with the imposed conditions so that its currents flow more and more easily. The three times optimal shape for lower ratios of a is achieved when the cavity has a higher penetration into the solid domain and for a thinner stem. As the magnitude of a increases, the bifurcated branch displaces toward the center of the solid domain and the number of highest temperature points also increases, i.e., the distribution of temperature field is improved according to the constructal principle of optimal distribution of imperfections.