Numerical modeling of vapor ejector working with ammonia–water mixture for application in absorption heat-transformer

Ammonia–water absorption cycles increasingly rely on ammonia vapor ejectors to improve system performance under unconventional operating conditions. However, their behavior under non-equilibrium condensation remains poorly understood, particularly in the presence of water. Even a small amount of water can alter nucleation, droplet growth, and thermodynamic fields, thereby affecting ejector dynamics and flow characteristics. This study investigates the impact of non-equilibrium condensation through different multiphase modeling approaches. Three models are developed in this work. The first model accounts for ammonia condensation and is validated against experimental data for a pure ammonia nozzle. The second model considers condensation in an ammonia–water mixture, assuming that the amount of liquid formed is sufficiently small to maintain a constant vapor phase composition. Finally, a third model is developed to account for changes in vapor phase composition resulting from the condensation process, and its predictions are compared with those of the other approaches. The results show that 2% water in the ammonia–water vapor mixture triggers earlier condensation, modifies local pressure and temperature, and influences nucleation and droplet growth. These findings highlight the importance of incorporating water effects and appropriate condensation modeling for accurate ejector design and performance evaluation.