Falling-film heat exchangers used in desalination systems: A review

• Research on falling-film heat exchangers used in desalination systems, especially multi-effect distillation systems, is critically reviewed to assess the state of the technology. • The presence of non-condensable gasses in desalination systems leads to reduced performance for both condensation and evaporation. • Research on scaling in horizontal-tube, falling-film evaporators in multi-effect distillation systems is insufficient in the open literature. With growing demand for fresh water, there has been an increasing interest in energy-efficient desalination technologies. Falling-film-based, multi-effect distillation (MED) systems have been extensively deployed world-wide. The performance of such systems heavily depends on the efficiency of the evaporation process. In the current paper, research on falling-film heat exchangers used in desalination systems, especially MED systems, is critically reviewed to assess the state of the technology. The review includes falling-film evaporation mechanisms, system operation, and scaling issues. Finally, opportunities for further application and areas where more research is needed are identified.