An extensive set of experiments was conducted to examine inflow effects of constricted convection on natural air cooling of plate fins. Several configurations were tested in the experiments: fins in an infinite cooling air; fins shrouded by a vertical side plate; fins shrouded by a horizontal lower plate; and fins enclosed by Both lower and side plates. For closely spaced fins with high aspect ratios, a side shroud shows virtually less effect on the array heat dissipation. A lower shroud, however, effects a considerable reduction in the heat dissipation when the shrouded clearance becomes smaller than a critical space. Significantly, enclosing the fins with both lower and side shrouds results in a serious deterioration in the heat dissipation, the deterioration is closely dependent on the side shrouded clearance as well. From the results, an optimum enclosing configuration appears to exist corresponding to the maximum volume heat dissipation rate.