Aerothermal performances improvement by novel stepped zebra-ribs in two-pass channel

Abstract

The novel stepped zebra-ribs (SZR) are invented for improving the aerothermal performance of a channel flow. The measured endwall Nusselt number map, Fanning friction factor, and aerothermal performance index for the enhanced two-pass channel are correlatively examined with the flow structures predicted by ANSYS code. The heat transfer enhancement (HTE) mechanisms generated by the stepped zebra-ribs, which are characterized as scrolling sectional vortices, periodically broken boundary layers, and turbulence promotions act together to significantly promote the HTE effectiveness. At the Reynolds numbers between 5000 and 15,000, the area-average Nusselt numbers and Fanning friction factors over the ribbed endwall are respectively raised to 5.97–4.9 Dittus-Boelter (DB) references and 13–9.6 times of Blasius eq. (B-E) levels to give rise to the outstanding API values of 2.65–2.39. The heat-transfer and pressure-drop correlations of the two-pass channel with the SZR are devised to assist the relevant applications.