Experimental study on heat transfer augmentation in viscoelastic turbulent channel flow by two-dimensional orifice

Viscoelastic turbulence, such as surfactant/polymer solution flows, would produce reductions of drag and heat transfer in smooth channels, but characteristics of their flows over roughened surfaces or bluff bodies are still difficult to be predicted. This is due to the fact that the fluid viscoelasticity depends on the local shear stress as well as the liquid conditions, e.g., temperature and concentration of the solution. We performed experiments on the heat-transfer reduction/augmentation in the drag-reducing surfactant solution flowing through a rectangular orifice. In the result, heat-transfer enhancement by the orifice were found in both water and surfactant solution, although their Reynolds-number dependencies are different. Highly enhanced heat transfer was observed in the reattachment zone just behind the orifice. We examined also the temperature- and concentration-dependencies of the Nusselt number, and compared them with the results for the smooth channel.