Effects of combined ribs and delta-

Effects of combined ribs and delta-winglet type vortex generators (DWs) on forced convection heat transfer and friction loss behaviors for turbulent airflow through a solar air heater channel are experimentally investigated in the present work. Measurements are carried out in the rectangular channel


An experimental study has been conducted to investigate airflow friction and heat transfer characteristics in a solar air heater channel fitted with the combined triangular rib and theDWturbulators for the turbulent regime, Re=5000 to 22,000. The experimental result reveal that the combined rib and the DWprovides considerable heat transfer augmentations, Nu/Nu0=2.3–2.6 and also causes a moderate pressure drop increase, f/f0=4.7–10.1, depending on the attack angle and Re values. The Nu augmentation tends to decrease slightly with the rise in Re. The use of combined rib and PD-DW at lower angle of attack provides higher heat transfer of about 40–65% and better thermal performance than the rib/theDWalone, leading to more compact heat exchanger. The best operating regime for using these compound turbulators is found at the PD-DW arrangement, lower attack angle and/or Re values.