Mass/heat transfer in a ribbed passage with cylindrical vortex generators: The effect of generator-rib spacing

The effect of vortex generators on the heat transfer from internally ribbed passages is studied experimentally using a mass transfer technique. Cylindrical vortex generators placed directly above the ribs have been used in this study. Results are reported on the effect of the spacing between the vortex generator and the ribs. Detailed distributions of the Sherwood number contours and the centerline Sherwood number distributions are presented. Reynolds number values of 5000, 10,000, and 30,000 are studied and three generator-rib-spacing/rib-height (s/e) values of 0.55, 1, and 1.5 are considered. It is shown that at small generator-rib spacings (s/e=0.55), the two act as a single element, and lead to a retardation of the shear layer development past the reattachment point. This is generally associated with lower heat transfer. At a larger generator-rib spacing (s/e =1.5), the generator wake and the rib shear layer interact with each other to promote mixing and heat transfer.