Heat transfer enhancement in a turbulent natural convection boundary layer

An experimental study on heat transfer enhancement for a turbulent natural convection boundary layer along a vertical flate plate has been performed by inserting two-dimensional flat plates (heat transfer promoters) into the boundary layer. The heat transfer rates markedly very with the position, yaw angle and size of the promoters, and it is confirmed that the promoters are effective to control turbulent heat transfer characteristics of the natural convection boundary layer. Also, the visualization of flow with smoke and laser sheet and simultaneous measurements of the flow and thermal fields with hot- and cold-wires in the downstream region of the promoter have been conducted to clarify the cause of the increase in local heat transfer rates. As a result, it is observed that the low-temperature large vortices induced by the promoter invade very near the wall and the heat transfer enhancement occurs. (author)