Compared with single-phase laminar pipe flow, two-phase bubble-train flow shows a significantly increased rate of mass transfer between liquid and wall, The present work is a study of this effect over a wide range of the governing variables. The problem has been numerically simulated and experimentally examined using the copper dissolution method. Furthermore, a mathematical correlation for the Sherwood-number of the system is presented and the mechanism of transport enhancement is elucidated. (C) 2003 Elsevier Science Ltd. All rights reserved.