Heat transfer and friction characteristics in a rectangular channel with rib-grooved turbulators

This paper presents a novel configuration of rib-grooved turbulators in order to enhance the thermal performance of internal cooling. Seven turbulent channel configurations with different groove width-to-rib length (W/a) ratios are investigated, and the ribbed channel is also included as a baseline. The influences of rib-grooved turbulators and groove width on the thermal performance of internal cooling are examined. The thermal performance, in terms of flow and heat transfer characteristics and friction characteristics, is analyzed with Reynolds numbers ranging from 12 000 to 27 000. The results show that the fluid boundary layer is broken by the rib-groove turbulators and part of the fluid flow passing the grooves (called the groove flow). The groove flow impinges on the recirculation flow downstream the ribs (vortex C), and then it is forced to move upward to mix with the mainstream. The averaged Nusselt number and friction factor decrease with the increase in groove width. The case with W/a of 2 yields the lowest averaged Nusselt number and friction factor. The thermal performance index, which is determined by the heat transfer performance and friction characteristics, exhibits a declining trend with increasing Reynolds numbers. The highest level of thermal performance is observed in the case with W/a of 1.02.