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ISSN Online: **2688-7231**

ISBN Online: **978-1-56700-524-0**

Proceedings of the 26thNational and 4th International ISHMT-ASTFE Heat and Mass Transfer Conference December 17-20, 2021, IIT Madras, Chennai-600036, Tamil Nadu, India

A detailed analysis is performed to examine the effect of angles of attack and radial locations of a pair of rectangular-winglet-type vortex-generators on heat transfer enhancement. The winglets are placed on the annular fin of a circular fin-tube cross-flow heat exchanger. One of the most effective ways to enhance the heat transfer from the surfaces of the heat exchangers is to insert protrusions such as delta-wings, delta-winglets, or rectangular-winglets, which are called vortex generators [1]. These protrusions create longitudinal vortices that take the fluid from the underside of the wake, swirl it around the upper side, entraining fluid from the periphery to the center of the vortices. The mechanism finally culminates in the disruption of the growth of the thermal boundary layer and the heat transfer coefficient is enhanced. The effectiveness of vortex generators depends on the shape, position, and angle of attack. The present study examines the performance of rectangular-winglet type vortex-generators with common-flow-up arrangement [2] placed at different radial positions and angles of attack on an annular fin. Such annular fins are integral parts of circular fin-tube heat exchangers. Numerical simulations have been performed by solving three-dimensional Navier-Stokes equations together with the energy equation. The performance of the vortex-generators is examined by using the spanwise average Nusselt number, friction factor, and quality factor. It is observed from the results that the performance of a pair of rectangular-winglets depends on the position and the angles of attack.