Turbulent heat transfer measurement of a jet impinging on the rib-roughened convex surface

摘要

The loca Nussetl numbers have been measured for a round turbulent jet impinging on the convex surface with and without rib roughness. Liquid crystal/transient technique was used to determine the Nusselt number distributions along the surface. The surface temperature was measured using liquid crystal and a digital color image processign system. The experiments were made for the jet Reynolds number Re = 23,000. The dimensionless nozzle-to-surface distance L/d = 6 to 10, the dimensionless surface curvature d/D = 0.056, and the various rib types (height d_l = 2 mm, pitch p = 12 to 32 mm). It was found that the average Nusselt numbers ont he convex surface with rib roughness are higher than those without ribs, due to an increase in the turbulent intensity caused by flow separation. Recirculation and reattachment on the wall surface.