Effects of tapes with double-sided delta-winglets on heat and vortex characteristics

An experimental study was carried out for tapes with double-sided delta-winglets under different geometrical and flow parameters, including angles of attack (90°, 60° and 30°), winglet heights (8, 12 and 16 mm), pitch arrangements (25, 50 and 75 mm) and Reynolds numbers (3690, 10493 and 16906). By using the Taguchi experimental-design method, the optimum parameters of the turbulator were determined by obtaining the Nusselt number, friction factor, amplitude of fluctuation pressure of the vortices and the vortex-shedding frequency. First of all, each goal was optimized, separately. Then, all the goals were optimized together, considering the priority of the goals, and the optimum results were obtained at a Reynolds number of 16906, 25 mm pitch, 8 mm height of winglet and 30° angle of attack, so that vortex-shedding frequencies are maximised. For lower frequencies, optimum conditions occurred at a Reynolds number of 16906 for 75 mm pitch, 8 mm height of winglet and 60° angle of attack.