Effect of transverse misalignment on natural convection from a pair of parallel, vertically stacked, horizontal cylinders

Experiments were carried out to determine the effects of transverse misalignment on the natural convection heat transfer characteristics of a pair of equitemperature, parallel horizontal cylinders situated one above the other. During the course of the experiments, which were performed in air, the transverse offset was varied systematically at several fixed vertical separation distances, while the Rayleigh number ranged from 2 × 10⁴ to 2 × 10⁵. At small vertical separations, transverse offsetting causes an increase in the upper-cylinder Nusselt number (up to 27 percent) compared with that for the perfectly aligned case [i.e., no offset) and, furthermore, the Nusselt number is responsive to small offsets. On the other hand, at larger vertical separations, the offset-affected upper-cylinder Nusselt number is lower (by up to 20percent) than the no-offset value but is quite insensitive to small offsets. At large transverse offsets, the upper-cylinder Nusselt number slightly exceeds that for a single cylinder, with the increase being due to a horizontal airflow induced by the acceleration of the lower cylinder’s plume. For all of the cases investigated, the lower-cylinder Nusselt number was virtually identical to that for a single cylinder.