Impingement heat transfer at a circular cylinder due to an offset or non-offset slot jet

Abstract

Heat transfer coefficients were measured on a circular cylinder subjected to the crossflow impingement of a slot jet. In one set of experiments, the symmetry plane of the jet was aligned with the axis of the cylinder, while in other experiments the jet was offset from the cylinder. In addition to the offset, parametric variations were also made for the width of the jet-inducing slot, the distance between the slot and the cylinder, and the Reynolds number. Supplementary flow visualization experiments showed that even in the presence of offset, the jet impinged on the cylinder, although not at the cylinder apex as in the aligned case. It was found that the heat transfer coefficient increased with slot width and Reynolds number but decreased with slot-to-cylinder separation distance and offset. The effect of offset is accentuated for narrow slots and at small slot-to-cylinder separation distances. The largest measured offset-related reduction in the heat transfer coefficient was slightly in excess of 50%.