Numerical Investigation of Hydrothermal Performance and Entropy Generation through Backward Facing Step Channel with Oval Rib

Abstract

This study presents a numerical investigation of laminar forced convective flow through a backward-facing step channel integrated with an oval rib, spanning a Reynolds number range of 200-1000. Two-dimensional governing equations of continuity, momentum, and energy were solved in body-fitted coordinates employing the finite volume approach. The investigation sought to elucidate the effects of rib height, rib location, and the Reynolds number on key parameters including the reattachment length, friction factor, total entropy generation, average Nusselt number, and the hydrothermal performance factor. Results demonstrated that both the average Nusselt number and the total entropy generation exhibited an increase with the augmentation of rib height, and conversely, a decrease with the expansion of the step-to-rib distance. In addition, the friction factor was found to increase in proportion to the distance between the rib and the step, and decrease with the rise in rib height, particularly when the Reynolds number exceeded 400. Furthermore, the reattachment length of the primary vortex was observed to increase with the step-to-rib distance and decrease with the rib height. The study concludes that a backward-facing step channel utilizing an oval rib, with a rib height of 0.3 and a rib-to-step distance of 2, delivers an optimal performance factor around 2.1 at a Reynolds number of 400. Therefore, the implementation of the oval rib in a backward-facing step channel is recommended for high thermal performance and compact heat exchanger design.