The pressure drops and the interfacial convective heat and mass transfer coefficients in packed beds saturated with a gaseous mixture containing hydrogen are studied by direct numerical simulation in the Darcy regime flow (Re-d <= 1) for both random and structured packings of the beds. For conditions with the Knudsen number Kn <= 0.01, the effective thermal conductivity of the random packings was calculated for various filling gases (H-2, He, N-2, and Ar). Additional correlations of the mathematical model for variable heat and mass transfer in porous hydrogen-absorbing media and based on the approximation of interpenetrating continua were specified from the received results. The developed mathematical model was used in numerical simulations of the heat and mass transfer processes in practical hydrogen storage devices. These results will be presented in the second part of the paper. (C) 2013 Elsevier Ltd. All rights reserved.