Heat transfer and fluid flow behavior of air in square duct heat exchanger inserted with v-downstream winglet turbulators

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 (). 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.