Secondary flows and extra heat transfer enhancement of ribbed surfaces with jet impingement

Abstract

Previous experiments recognize that substantial heat transfer augmentation is achieved by adding ribbed turbulators after jet impingement with cross flow present. The present study investigates the fundamental working mechanism in a typical turbulent channel flow. Conjugate CFD simulations are employed for ribs, jet impingement, and their combinations. Flow characteristics and drawbacks for the individual and combined enhancement techniques are highlighted. New analysis on the coupled design arrangement reveals that the counter-rotating vortices generated by the jet flow can energize inter-rib recirculating vortices and promote spanwise convection. With an optimal design combination arrangement, extra heat transfer benefit is achieved beyond that associated with simple superposition of rib and jet impingement techniques. As such, the resulting thermal design approach is confirmed using published experimental data, and thus, is useful for surface heat transfer augmentation optimization in practice.