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Heat Transfer and Fluid Flow Behavior of Air in Square Duct Heat Exchanger Inserted with V-downstream Winglet Turbulators

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Suriya Chokphoemphun, Sanhawat Thongdaeng and Pongjet Promvonge

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This work present the experimental investigation on heat transfer enhancement and

thermal performance in a square-duct heat exchanger inserted with 45º V-downstream

winglet turbulator is carried out by varying velocity of air in the turbulent regime for

Reynolds numbers (Re) ranging from 4000 to 26,000 in the test section with a constant

wall heat flux condition. Influents of four different pitch lengths; P=22.5, 33.75, 45 and 90

mm (PR=P/H=0.5, 0.75, 1 and 2) and three different winglet heights, e=6.75, 9 and 11.25

mm (BR=e/H=0.15, 0.2 and 0.25) were inserted diagonally and placed in the core flow area

into the test duct on heat transfer rates in the term of Nusselt number (Nu), pressure loss

in form of friction factor (f) and thermal performance (η). It was found that the 45º V-downstream

winglet is provided the Nu and f higher than the smooth surface around 6.0 to 8.7

times and 37 to 170 times, respectively depending upon operating conditions while the

thermal performance are about 1.50–2.06. The maximum thermal performance for using

45º V-downstream winglet turbulator is 2.06 at Re=4100, BR=0.2 and PR=1.0 in this

experiment.

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V-downstream winglet; square-duct heat exchanger; thermal performance