Thermal studies of a heated cylinder placed near a plane surface

Abstract

Local and average Nusselt numbers have been experimentally determined around the circumference of a uniformly heated right circular cylinder placed near a plane surface in a cross flow of air. Experiments were carried out for Reynolds numbers ranging from 16,000 to 153,000, three plate lengths and varying cylinder to plate spacings. The variations of the average Nusselt number as a function of gap spacing was found to exhibit an interesting and unexpected trend. The average Nusselt number exhibited a minimum value when the cylinder was resting on the plate and attained a maximum value at a gap spacing of approximately one to two cylinder radii. Flow visualization studies together with measurements of the vortex shedding frequency in the cylinder wake indicate that when the plate is with in approximately one cylinder radius of the cylinder, it inhibits the formation of the regular vortex pattern that forms in the wake of a free cylinder. This has a strong influence on the base Nusselt number which, in turn, exerts a controlling influence on the magnitude of the average Nusselt number.