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The objective of the present research is to investigate swirling impinging jets (SJ) heat transfer on the impinged surface under a uniform wall heat flux boundary condition. Swirling impinging jets (SJ) were induced by multiple twisted nozzles which were arranged in 3 rows and 3 columns (3 x 3). Each nozzle had an inner diameter of 9.35 mm and a length of 93.5 mm. In addition, conventional jet (CJ) were also tested for comparison. Effects of jet spacing of (2.0 < S/D < 6.0) and twisted nozzle with pitch ratio of (23 < P/D < 93) were examined. Experimental results showed that the SJ gave better heat transfer rate than the CJ since tangential force of SJ enlarged an impinged area. At small jet-to-plate spacing (2.0 < L/D < 4.0), the effect of swirling flow on heat transfer enhancement was significant. For the studied range, the swirling impinging jet (SJ) enhanced Nusselt number up to 21.1% in as compared the conventional impinging jet (CJ) at jet spacing of S/D = 2.0 and the lowest pitch ratio of P/D = 23.
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Faculty of Engineering and Technology
Mahanakorn University of Technology
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