Emprego da simulação numérica na determinação do espaçamento ótimo entre aletas, dispostas em um tubo, submetido a transferência de calor por convecção natural.

Abstract

The use of fins in heat exchangers is applied aiming at increasing efficiency in the heat transfer process. This work studies the optimal spacing in convective heat transfer on fins arranged on a tube, using two classical geometries, circular fins, and square fins. The results obtained with the use of empirical correlations proposed in the literature were compared with the results obtained with numerical simulation. The governing equations, Navier-Stokes Equations, Energy, and Mass Conservation, were approximated using the Finite Volume Method, which is implemented in the commercial software ANSYS CFX 2023R1 ©. In numerical simulations, square and circular fins were analyzed by modifying the spacing and dimensions of the fins, subjected to natural convection. Three sizes were considered for the two fin geometries, and seven spacings between them were considered. This work presents the values of heat transfer rates as a function of spacing, the ratio between fin and base tube diameters, and the ratio of fin height to tube diameter. It also shows: the Nusselt number, the behavior of the convective coefficient, and the temperature and velocity fields for the simulated cases. The results indicate that the optimal spacing is of the order of 6 mm and that the discrepancies between the numerical and theoretical studies were within the range of 13% and 16%