Numerical study on the heat transfer performance and efficiency in a rectangular duct with new winglet shapes in turbulent flow

Abstract

The present study numerically investigates the three-dimensional flow and heat transfer characteristics in a rectangular duct equipped with four different winglet shapes. Besides the conventional delta winglet, the new delta-cut, arrow and X winglet are studied. To evaluate the winglet’s performance, Nusselt number, friction factor, and thermal efficiency enhancement are compared to that of a smooth duct. All simulations are carried out for Reynolds numbers ranging from Re=4000 to Re=12000. The winglets are arranged as single and 2×2 configuration. In the multiple arrangement, the longitudinal pitch between the winglet rows is varied as 5, 7 and 9 times the channel height. The results show the highest Nusselt number enhancement of 12.4% for the case of single winglet and 35.5% for the 2×2 arrangement for the delta winglet, accompanied by the maximum pressure drop. The arrow winglet achieves the maximum efficiency augmentation of 7.2% for single and 9.5% for 2×2 arrangement. The analysis of flow structure shows a contribution of secondary vortices occurring besides the primary longitudinal vortices behind the winglets to heat transfer enhancement. The longitudinal pitch variation in multiple winglets arrangement has been found to have a negligible influence on the heat transfer rate, pressure loss, and efficiency.