The falling liquid film has become a popular means of transferring heat and mass from a vapour to a binary liquid, especially in gas-fired heat pump systems. Ideally, the required amount of heat and mass transfer can be accomplished by using a simple cylindrical tube; however, increasingly stringent size and weight requirements for the machine generally prohibit use of the simple cylindrical surface and other, more complex, surfaces have been sought that are believed to have a higher absorption capacity. Thus, absorption of water into a lithium-bromide-water (LiBr-H2O) film on a spine-finned or spiny tube is considered. The governing equations for the fluid flow and heat and mass transfer problems are derived and it is shown that solution to the full equations for use in a design is not practical. Dimensional analysis is employed to simplify the governing equations considerably when the influence of surface tension is small. It is shown that on the local spine scale, the temperature distribution is conduction-dominated and when the influence of surface tension is small, the mass transfer problem is governed by essentially smooth tube dynamics. A model for the performance of the tube is developed in part 2.

KEYWORDS: year 1996, calculating, performance, absorbers, heat flow, finned tubes