Comparison of the performance of falling film and bubble absorbers for air-cooled absorption systems

Small capacity, air-cooled NH3–H2O absorption systems are becoming more attractive in applications where the input energy can be obtained for free (e.g., solar energy, exhaust gases of engines), due to the increasing price of the primary energy. One of the main difficulties for a wider use of absorption machines is the necessary high initial investment. For this reason, the development of air-cooled systems could be an important achievement for low capacity applications. In this work, two types of air-cooled absorber have been modelled: (i) falling film flow; (ii) bubble flow. The two models have been validated with experimental data obtained from a developed testing device and published numerical results of other authors from another model. The agreement is acceptable for both cases. Finally, a parametric study has been done for air-conditioning and refrigeration in a mobile application taking advantage of the exhaust gases of the engine. In both cases, the performance of the bubble absorber has been higher.