In order to predict the pressure drop and the mean void fraction for bubbly flows in packedbeds, a new one-dimensional (1-D) model is proposed. The balance equations for both phasesare derived from local Eulerian two-fluid equations which are spatially averaged at amesoscale, that is, at a length-scale large compared with the microscale that characterizes thefixed bed. This model, that differs from previous mechanistic models, has been supplementedby closure laws for the liquid-solid and the gas-liquid interactions, those structures accountfor the flow dynamics at the pore scale. It is first experimentally demonstrated that, in diluteconditions, the bubble-size distribution only depends on the pore size, when the later is smallerthan the capillary length scale. It is also shown that the mean-bubble dynamics is similar tothat of a slug, with a relative velocity at mesoscale linearly increasing with the liquidsuperficial velocity. Besides, that relative velocity monotonically increases with the gas flowrate ratio, a behavior that can be attributed to the formation of preferential paths for the gasphase. Concerning the liquid-solid interactions, the two-phase flow pressure drop scaled by itssingle-phase flow counterpart at the same superficial liquid velocity is predicted to linearlyincrease with the void fraction, with a prefactor evolving with the Capillary number. Theseclosures prove consistent with available experiments, both in upward and in downwardsituations. Although these proposals deserve to be further tested over an extended range offlow parameters, this model paves the way to reasonably accurate predictions of bubbly flowsin packed beds able to account for refined parameters related with the flow dynamics.