Combined natural convection and radiation heat transfer from a shrouded vertical fin array

Abstract

Experiments were performed to determine the combined-mode natural convection/radiation heat transfer characteristics of a shrouded array of rectangular, vertical fins. The investigated parameters included the height and longitudinal length of the fins, the clearance gap between the shroud and the fin tips and the fin-to-ambient temperature difference. Shroud walls having different thermal characteristics were used (highly conducting and insulated). For each configuration, the Rayleigh number ranged from 40 to 700. It was found that the positioning of a shrouding surface close to the fins decreased the rate of combined-mode heat transfer when compared to the unshrouded case. Greater heat transfer rates were found for the conducting wall shroud in comparison with the insulated one. Calculations performed showed that, when the clearence gap between the shroud and the fin tips was zero, the convective component of the total heat transfer was dominant. For other clearence gaps, the contribution of radiation was of the same order of magnitude as the convective one. The contribution of the radiative component was greater for small values of the Rayleigh number and for clearence gaps different from zero.