Experimental investigation of heat transfer in a channel with new winglet-type vortex generators

Both new punched triangular vortex generators (PTVGs) and punched rectangular vortex generators (PRVGs) have been developed. Both the triangular and rectangular vortex generators were directly punched from the longitudinal winglet at attack angles of 15°, 45° and 75°, respectively. Measurements were carried out for a rectangular channel of an aspect ratio of AR = 2, for a winglet transverse pitch (S) to a longitudinal winglet height (e) ratio of S/e = 0.59, and a winglet height (e) to a channel height (H) ratio of e/H = 0.6. The parameters included the location of the punched vortex generator on the longitudinal winglet, the geometric shapes of the punched vortex generators, and the attached angle of punched vortex generators. The Reynolds numbers considered for the channel flow case (based on the hydraulic diameter) ranged from 3288 to 37,817. The heat transfer results were obtained using the infrared thermal imaging technique. The heat transfer results of the vortex generators were compared with those of a smooth plate. The best heat transfer performance was obtained with the PTVGs. The presence of the vortex generators produced higher heat transfer coefficients than the smooth plate surfaces. Correlations were developed for the averaged Nusselt number for the PTVGs and PRVGs. Results showed a 23–55% increase in heat transfer due to the use of vortex generators. These vortex generators show a more significant increase in heat transfer coefficient for channel flows.