Abstract
This study introduces for the first time a rectangular winglet vortex generator with multi-perforations (MPRWVG) and examines its impact on flow and heat transfer when inserted into a uniformly heated tube to create mixed vortices under turbulent conditions. The primary objective is the maximization of thermal performance for enhanced energy savings and the optimization of the Nusselt number (Nu) and friction number (f) to reduce the size of heat exchangers. Emphasis is placed on the analysis of thermal and pressure loss characteristics, including entropy generation. The arrangement of the MPRWVGs features four angles of attack (α=0°,15°,30°,45°) and four different numbers of perforations (N=1,2,4,6), and three uniform pitches (P=25mm,50mm,75mm), all uniformly fixed on a ring. The results indicate that the generation of multi-jets from the perforations, along with their interactions with each other and other longitudinal vortices, significantly affects Nu and f characteristics. As the number of N increases, its advantage in enhancing heat transfer becomes more apparent. Among the three research parameters, the value of α has a significant impact on Nu and f. The MPRWVGs demonstrate a potential for up to a 7.73-time enhancement in Nu and a 136.88-time increase in f compared to a plain tube, highlighting their effectiveness. The minimization of the Bejan number (Be) is observed with decreased P and N values and increased α. The lowest Be value of 0.997 is achieved at P=25mm, N=1, α=45°, and Re=13,664. The maximum thermal enhancement factor of 1.59 is recorded at P=25mm, N=1, α=45°, and Re=7,454.
Published Version
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