This book is intended for engineering graduate students and research and development scientists who are interested in mass (and heat) transfer in pipe bends under single and two phase flow. The emphasis is on the mass transfer, which is the rate limiting process in Flow Accelerated Corrosion. In particular, the effect of the flow dynamics under single phase flow and the phase interaction and redistribution under annular air-water two phase flow on the local mass transfer distribution is presented. The mass transfer distributions and regions of high mass transfer in different bend geometries are correlated to areas of failure under flow accelerated corrosion observed in the nuclear industry. The book presents a novel technique to obtain detailed mass transfer measurements in intricate geometries with evolving surface roughness.