A review of falling film evaporation under different surface structures and external disturbances

Falling film evaporation has been proposed as a promising alternative to traditional pool boiling heat exchangers due to advantages such as low-pressure drop, heat transfer improvement and refrigerant charge reduction. This paper provides a comprehensive review of recent advancements in falling film flow and heat transfer characteristics, specifically focusing on various surface structures, including smooth plates, corrugated plates, vertical tubes, and horizontal tubes. In the case of film flow on plates, this review highlights key aspects such as film thickness, film wave evolution, wettability, and heat transfer properties. The study further reviews findings on film flow along both the inner and outer surfaces of vertical tubes, as well as horizontal round tubes and non-round tubes. The enhanced tube can be divided into tubes machined with fins and coated with material. Noteworthy findings regarding flow pattern transitions, film thickness, and heat transfer characteristics on horizontal tubes are comprehensively outlined. Furthermore, the impact of external disturbances on film flow and heat transfer is also reviewed. Finally, several challenges and prospective directions for future research are concluded.