Effect of Dimple Configuration on Heat Transfer Coefficient in a Rib-Dimpled Channel

Abstract

The effects of dimple depth, pitch, size, and alignment on the heat transfer coefficient in a rib–dimple channel were experimentally investigated. The heat transfer coefficient in the rib–dimple channel was measured using the liquid crystal technique, and the friction factor was evaluated. The channel aspect ratio was 4; and three Reynolds numbers of 30,000, 40,000, and 50,000 were tested. For the systematic investigation of the effect of dimple configuration, rib–dimple cases with three dimple depths (0.11 to 0.33 of dimple diameter), three dimple pitches (1.2 to 1.5 of dimple diameter), three dimple sizes (11 to 14.8 mm), and two dimple alignment methods were compared. The rib thickness and height were both 5 mm, and the rib pitch to the rib height ratio was 10 for all cases. Results showed that the rib–dimple cases improved the Nusselt number ratio and the thermal performance factor compared with the rib-only case. For the given channel aspect ratio and the rib configuration, the reference case with three rows of dimples between ribs, a dimple diameter of 11 mm, a dimple depth to diameter ratio of 0.22, a dimple pitch to dimple diameter of 1.2, and dimples aligned along ribs showed the best thermal performance, but the heat transfer augmentation was the highest for the densely fabricated dimples case.