The forced convection heat transfer characteristics in high porosity open-cell metal-foam filled tube heat exchangers are analysed in this paper. The Brinkman-extended Darcy momentum model and two-equation heat transfer model for porous media are employed for the analysis of the heat transfer performance. The morphological effects of metal foams on overall heat transfer are examined. The optimal foam-area ratio for a metal-foam filled counter-flow tube-in-tube heat exchanger is predicted. The study shows that the thermal performance of a metal-foam heat exchanger can be superior to that of conventional finned tube heat exchangers. (c) 2006 Elsevier Ltd. All rights reserved.