Heat Transfer Enhancement with Semicircular Cylinder Turbulence Promoters-Effect of position of a turbulence promoter relative to film thickness-

Heat transfer enhancement in a rectangular duct with semicircular cylinder turbulence promoters are investigated for high-Prandtl number fluid by the visualization of flow and measurement of the mass transfer coefficient, utilizing an electrochemical method. In this study, we newly introduced NTF, a normalized position of a turbulence promoter relative to the film thickness for a smoothed duct. The performance ratio, η, for semicircular cylinders with their arcs downward depends strongly on NTF and shows the highest value when just a small part of a promoter is in the film. Semicircular cylinders are found to be the most effective shape for heat transfer enhancement.