Unsaturated flow through thin layers of porous media are encountered in many industrial applications, including fuel cells and liquid-absorbing hygiene products such as wipes, paper towels, and diapers. Simplified and efficient closure models are very valuable for understanding fluid flow and transport mechanisms in thin porous media and for the development and design of these products. In this study, a new explicit inter-layer mass exchange closure model is rigorously developed and incorporated into the macroscopic mass balance model in order to obtain a complete set of equations which can be used to describe the absorbency processes in thin porous media and to predict the temporal and spatial behaviors of variables such as saturation, porosity, and layer thickness. The developed 2D averaged macroscopic model will enormously improve the computational speed, allowing one to develop a fast and reasonably accurate simulation of the unsaturated flow. Furthermore, the new closure model will account for the mass exchange between the interior adjacent layers and will include the liquid-absorption effect to better understand the transports mechanisms for characterizing absorbent materials and validating models. The developed closure model is validated for the water flooding problem arising in polymer electrolyte membrane fuel cells and can be adapted and used in the future to solve new interesting thin porous media-related problems of common interests. (C) 2019 Elsevier Ltd. All rights reserved.