AMMONIA-WATER ABSORPTION PROCESS ON FALLING FILMS AT VERTICAL AND INCLINED PLATES

Based on the falling film technology, this paper presents an analysis of the process of ammonia-water mixtures absorption on inclined flat plates at several tilt angles by the finite-difference method. Overall balance relations of mass, ammonia species, and energy along with heat and mass transfer experimental correlations were solved for a set of control volumes discretized over the plate lengthwise. First, typical operational conditions of a simple-effect absorption refrigeration cycle were set in order to define the range of interest. Next, a nondimensional analysis of the absorption process was carried out for several plate inclination positions in several operational conditions, including: plate length, plate inclination angle, surface temperature, and inlet thermodynamic state of the liquid and vapor phases. The results showed that the optimum absorbing plate angle was at the vertical position. Two performance criteria were used to evaluate the absorption process: thermal effectiveness and mass transfer effectiveness. Among all the tested conditions, the thermal effectiveness was always higher than the mass effectiveness in the same conditions. Finally, the numerical results of the falling film absorption process were successfully validated with experimental data available in the open literature.