A three-dimensional calculation method has been further developed to include two-phase, multi-component gas and heat transport processes. A set of momentum, heat transport and gas species equations have been solved for the whole duct by coupled source terms and variable thermophysical properties. The effects of the electrochemical reactions on the heat generation and mass consumption/generation have been taken into account as well. Liquid water saturation and its effects on the local current density has been predicted based on the calculated values of water vapor partial pressure and temperature. The unique fuel cell conditions, such as the combined thermal boundary conditions and mass transfer, have been employed as well. (C) 2004 Elsevier Ltd. All rights reserved.