An analogy-based method has been developed to evaluate heat and mass transfer characteristics of the falling liquid film on a vertical spirally wound Fir-finned tube that was newly developed for a LiBr/water absorption heat transformer. The model assumes the analogy between heat and mass transfer in a boundary layer of the liquid phase in the neighborhood of the interface between vapor and the falling liquid film. It evaluates beat and mass transfer coefficients by applying model equations to sub-divided sections and integrating them over the whole length of the liquid film. Absorption experiments of water vapor onto a falling liquid film were conducted using a bare tube and a corrugated tube as well as the spirally stacked finned tube, and heat and mass transfer characteristics in these tubes were compared. Mass transfer coefficients of the bare tube are almost the same as those of physical sorption process at a constant wall temperature reported in previous works, which show a similar independency of Film Reynolds number Re-f to that of Lamourelle and Sandall. The mass transfer coefficients of the spirally stacked finned tube have good performance, being 2.3 times that of the corrugated tube and 4.9 times that of the bare tube at Re-f = 1 x 10(3) under normal operational conditions. These characteristics were derived from a wavy flow generated on a spirally wound Fir-finned tube. Further, the model allows one to obtain local distributions of temperature, concentration and vapor absorption rate along a vertical tube, which cannot be evaluated by the conventional method using the logarithmic mean temperature and mean concentration.