The study of mass transfer behavior under a flow boiling condition has not been reported due to the complexities of the phenomenon and experimental difficulties. In the present study, a novel high temperature and pressure experimental flow loop as well as measuring techniques were developed to determine the mass transfer coefficient under the flow boiling condition to a level that no one else has achieved according to open literature. A new mass transfer correlation was proposed and proven to be suitable for representing the flow boiling mass transfer behavior. This work will provide a good base for further flow boiling mass transfer studies. (C) 2016 The Electrochemical Society. All rights reserved.