Measured Heat Transfer Coefficients at and Adjacent to the Tip of a Wall-Attached Cylinder in Crossflow—Application to Fins

Abstract

Wind tunnel studies encompassing both heat transfer measurements and flow visualization were performed for a cylinder in crossflow, with one end of the cylinder attached perpendicular to a wall and with the other end free. The focus of the work was to obtain heat transfer coefficients for the tip of the cylinder, for the tip-adjacent portion of the cylindrical surface, and for a portion of the cylindrical surface where there are no end effects. The flow visualization studies were performed to assist in the explanation and rationalization of the heat transfer results. They revealed the presence of spanwise flows adjacent to both ends of the cylinder, with accompanying modifications of the size of the separated region that washes the rear of the cylinder. The flow passing over the tip separates on the fore portion of the tip, but reattaches on the aft portion. The tip heat transfer coefficients are higher than those for the end-effect-free portion of the cylindrical surface, with deviations which grow with increasing Reynolds number (about a factor of two at Re = 25,000). For the tip-adjacent portion of the cylindrical surface, the coefficients are about fifty percent higher than those uninfluenced by end effects. The ramifications of these findings on the heat transfer analysis of fins are discussed.