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ISSN Online: 2377-424X

International Heat Transfer Conference 12
August, 18-23, 2002, Grenoble, France

Flow and Wall Heat Transfer Characteristics of a Longitudinal Vortex Generated by an Oblique Impinging Jet in Drag-Reducing Crossflow

Get access (open in a dialog) DOI: 10.1615/IHTC12.2960
6 pages

Abstrakt

In order to investigate heat transfer characteristics of drag-reducing flows in the application of far-district heating/cooling transport systems, the experiments on wall heat transfer rates were made in the wake behind an oblique impingingj et (OIJ) in a drag-reducingchannel flow. The workingfluid of both OIJ and the main channel flow was a non-Newtonian water solution of surfactant, Cetyl-Trimethyl-Ammonium-Chloride (CTAC), with the same mass concentration of sodium salicylate (NaSal). The CTAC concentration of the solution was set to be 0ppm (i.e. water) and 30ppm for the comparison between both cases. The nozzle of OIJ was mounted flush with the top wall of the test section, opposite to the heat transfer target wall. The Reynolds number, based on the cross-sectional area-averaged flow velocity and the duct height, was fixed at 5.0 × 103. It was found that small amounts of CTAC/NaSal added in water reduce the heat transfer coefficients drastically, and that this reduction could be locally recovered in the wake behind the OIJ. It was also found that the velocity ratio VR, the ratio of the jet velocity to the main flow velocity, changing from 2.4 to 8, had a dominant influence on the generation of a twin large-scale longitudinal vortex and the enhancement of local wall heat transfer rates. The twin vortex was observed to remain far downstream of the jet impingement regions.