One of the main drawbacks in modeling absorption chillers is the lack of justified hypotheses of heat and mass diffusion in an annular flow on the outer surface of horizontal tubes. Heat and mass transfer in diffusion is a three-dimensional problem with vector characteristics. This paper introduces the characterization of vapor-absorbent heat and mass transfer phenomena in three dimensional space to obtain steady state simulation results for single effect LiBr-H2O absorption chillers. It is thus possible for the first time to ascertain in the simulation that the heat and mass transfer characteristics are not uniform throughout the solution film. The diffusion boundary layer gradually becomes thicker towards the downstream tubes, which has previously been assumed but never confirmed in simulations. The radial component of the concentration field exhibits a potential for determining an optimum film thickness which enhances the system performance. The ability to use the proposed model with various absorbents and different cooling capacities increases its applicability. The model also offers the possibility to analyze different firing techniques at different temperatures. All the simulation results are consistent with the experimental data found in the literature. (C) 2013 Elsevier Ltd. All rights reserved.