Numerical study on the effect of co-current gas flow on the falling film flow characteristics outside the horizontal tube

Gas-liquid interactions are a ubiquitous feature of falling film exchangers in the nuclear industry. In the current research, a 2D model is established to explore the impact of co-current gas flow on the hydrodynamic characteristics of the falling film outside the horizontal pipes. This study examines different factors, including film flow rate, tube diameter, co-current gas flow velocity, transverse pitch ratio, distributor height, and inlet liquid temperature. The results revealed that the co-current gas flow significantly reduces the film thickness in the strong gas-liquid interaction zone and intensifies the fluctuating motion in the weak portion. Lead to the location of the minimum film thickness shifting upwards to around 90 degrees, which highlights the need to monitor this region to prevent the occurrence of film rupture or dry spots that negatively impact heat transfer performance. When the gas flow velocity is constant, the lower liquid film flow rate, the larger tube diameter, and the distributor height enhance the impact of gas flow velocity on the falling film, resulting in reduced liquid film thickness. A film thickness correlation applicable to both with and without co-current gas flow is established, and 91% of 900 prediction data fell within & PLUSMN;15% of the numerical results.

Automated summary

In this study, a 2D model is used to investigate the influence of co-current gas flow on the hydrodynamic characteristics of falling film outside horizontal pipes. The results show that the gas flow significantly affects the film thickness and motion. Factors such as film flow rate, tube diameter, and distributor height also amplify the impact of gas flow velocity on the falling film. A film thickness correlation is established and provides accurate predictions for both with and without co-current gas flow, with 91% accuracy.