Porous plates are commonly used in the external humidification devices employed in proton exchange membrane fuel cells. In this study, the effect of a ribbed surface on the water transfer characteristics of a porous plate is investigated experimentally to elucidate the process by which heat and mass is transferred from a high-temperature, high-humidity gas (wet air) through porous media to a low-temperature, low-humidity gas (dry air). Experimental results show that a porous plate with ribs can promote the water transfer between the two gases and that the water transfer ability of the plate is markedly improved when the ribbed side is oriented toward the humidified gas. (C) 2018 Elsevier Ltd. All rights reserved.