Abstract
An annular impinging jet was used to enable uniform cooling over a wide area of a flat wall. The ratio of an inner diameter to an outer one of a coaxial pipe was fixed at 0.64. The ratios of the inner pipe gas flow to the outer one, velocity ratio, were varied from 0 to 1.0 for the fixed outer pipe gas flow at 20m/s. The heat transfer characteristics on the impinging wall were examined. For the purpose of uniform cooling, the optimum velocity ratio was found to be approximately 0.1. The influence of the velocity ratio on the flow structure was clarified by the flow visualization.
