Flow structure and heat transfer of impingement jet

This paper presents the characteristics of flow behavior and thermal fields of both free and impingement jets issued from circular orifice nozzle at Re = 9,700. The flow behavior of a single round jet and impingement jet were observed by smoke flow visualization recorded by a high speed video camera with 5,000 frames per second. Heat transfer coefficient on the impingement surface was calculated varying the Reynolds number and the separation distance between nozzle exit and plate. Time-series analysis was applied to the visualization image to get the information of time variation of flow behavior. Probability distribution of vortex scale induced by the jet at discrete positions was investigated. Experimental results show that the potential core is not a continuous phenomenon with time and the frequency of vortex ring formation have similar features regardless of whether the impingement plate was set on or not, furthermore the time-series analysis with flow visualization images makes clear the detailed flow behavior.