A study of the heat transfer resulting from a heated jet impinging upon a cylinder

Abstract

The heat transfer resulting from the impingement of a heated circular jet upon a cylinder was experimentally studied. Velocity and temperature profiles of the impinging jets compared favorably with existing theoretical predictions and previous experimental work. Jet exit temperatures used did not appear to effect the velocity profiles of the impinging jets. Nusselt numbers at the stagnation point were found to only be functions of jet Reynolds number and impingement distance. They were also comparable to values obtained with flat plate targets for impingement distances less than 12 nozzle diameters. Local Nusselt number distributions along the longitudinal axis of the cylinder were found to behave in a manner similar to distributions on a flat plate target. Convex target curvature around the circumference of the cylinder increased the decay rate of local Nusselt numbers. This was attributed to convex curvature suppressing turbulent mixing. Local Nusselt number behavior in a region very near the stagnation point was independent of target geometry. Average Nusselt numbers were calculated based on various averaging areas. These average values were found to be strong functions of jet Reynolds number, impingement distance, and the averaging area. There was also a weak dependence upon the jet nozzle diameter to target cylinder diameter ratio. Compared to flat plate targets, the cylindrical target increased the importance of the averaging area and impingement distance in terms of calculating average Nusselt numbers.