AUGMENTATION MECHANISM OF MASS TRANSFER AMONG TURBULENCE PROMOTERS ON WALL SURFACE IN RECTANGULAR DUCT

Abstract

An experimental investigation was performed to study the mechanism for the augmentation of mass transfer by using turbulence promoters on the wall surface in a rectangular duct. The augmentation of local mass transfer among the turbulence promoters was measured by varying the diameter, the pitch of the promoters and the clearance between the promoter and the wall. In order to examine the augmentation mechanism, wall shear stress, mass transfer intensity and turbulence intensity at the wall were measured by an electrochemical method. Further, flow behaviors were measured by visualization. It was found phenomenologically that the augmentation of mass transfer with the clearance was caused by turbulence due to reattachment flow, large scale eddies and increase of shear stress due to flow jet under the promoters, and in case of no clearance, was caused by only turbulence on the wall surface.