Studies on mass transfer due to the presence of co-axially placed disc as insert promoter in circular conduit were presented in this paper. Limiting current data were obtained at various now rates using promoters of varying disc diameter and location of the disc. Wide range of variables are covered, disc diameter varied as 0.02, 0.03 and 0.04 In and location of the disc varied as 0, 0.25 and 0.5 m. Augmentation achieved is sixfold when the diameter of the disc is 0.03 m and location of the disc 0.25 m. A semi-theoretical model is developed in terms of geometric parameters and presented. (c) 2008 Elsevier B.V. All rights reserved.