Determinação de coeficientes convectivos de transferência de calor a partir da técnica de CFD para geometrias não-convencionais

Abstract

The convection heat transfer coefficients are essential for thermal project and process controls involving the mechanism of convection. In a solid-fluid system, the experimental evaluation of the film coefficient is not trivial because it depends simultaneously on the contact geometry, the fluid dynamics characteristics of the flow and the physicals properties of the fluid. Thus, an interesting alternative to estimate the convection heat transfer coefficient would be to apply CFD techniques, in which the Transport Equations are solved numerically and simultaneous. So, this work aimed to apply the CFD techniques to evaluate the film coefficients in conventional (plates, cylinders and spheres) and non-conventional geometries (ellipsoid and paraboloid) comparing them with values coming from the literature and create correlations according to the Reynolds and Prandtl numbers, as well as the slope of the flow. Statistical studies were carried out from the numerical results to obtain a mathematical correlation that describes the behavior of the physical phenomenon. The results showed that the convection heat transfer coefficient are directly proportional to Reynolds and Prandtl, with Reynolds being more impacting in the value of this coefficient than Prandtl. On the slope of the flow in relation to the solid surface, it can be seen that this one realizes a form of resistance, which in turn reduces the values obtained for convection heat transfer coefficient that is more accented to high values of Reynolds. Concerning the efficiency of heat transfer performance, it was found that, in parallel flow, the convection heat transfer coefficient is inversely proportional to the sphericity of the geometry.