A heat and mass transfer model for falling-film ammonia-water absorption over microchannel tube banks is presented. Three regions in the absorber were considered for absorption of vapor: solution pool, evolving droplets, and falling film. Flow of solution around the tube banks was modeled using a previously developed hydrodynamic model. Absorption in the solution pool and the droplet was assumed to be adiabatic, while the heat of absorption in the film was removed by circulating coupling fluid. This model was applied to measurements from a previous experimental study on a microchannel absorber. Most of the absorption was found to occur in the film region, while up to similar to 7% of the absorption was found to occur in the droplets. Heat transfer coefficients were estimated in the film region, and an empirical correlation for the film Nusselt number was developed. These models can be used to design ammonia-water falling-film absorbers. (C) 2019 Published by Elsevier Ltd.