Experimental aspects of heat transfer enhancement over various flow surfaces

Abstract

The heat transfer enhancement was experimentally investigated over the flat, concave, convex, and ribbed surfaces in a wind tunnel with the initial streamwise distance Reynolds number range of 4.0 x 10(5)-4.5 x 10(6) encompassing laminar, transitional, and turbulent flows. The velocity and turbulent intensities were measured by a constant-temperature hot-wire anemometer and temperatures by copper-constantan thermocouples. The results showed that the concave surface caused heat transfer to increase up to 55% in laminar, 30% in transitional, and 20% in turbulent flows, whereas the convex surface brought about heat transfer decreasing by 25% in laminar, 20% in transitional, and 15% in turbulent flows with respect to those of the flat plate. On the other hand, the ribbed surface with the same heated area caused much more heat transfer augmentation above the flat surface: 160% in laminar and 120% in turbulent flows.