Falling film hydrodynamics of horizontal egg-shaped tube under column flow

Egg-shaped tubes show strong potential for application in horizontal falling-film heat exchangers owing to their ability to enhance fluid distribution and film stability. However, the lack of understanding of their three-dimensional flow characteristics has constrained broader implementation and further performance optimization. In this study, the falling-film behavior around a horizontal egg-shaped tube under column flow is investigated numerically using the Volume of Fluid method and validated experimentally through chromatic confocal displacement sensing. The effects of tube geometry and Reynolds number on film thickness are examined and compared with those for elliptical and circular tubes. Results reveal that the egg-shaped tube exhibits a unique three-dimensional film-thickness distribution, characterized by an enlarged stable region and a reduced detachment region. For tubes with equal perimeters, the average film thickness of the egg-shaped tube falls between that of circular and elliptical tubes. The influence of the Reynolds number is most pronounced near the dimensionless axial location l*=0.5. Furthermore, a set of correlations is proposed for predicting the film thickness around egg-shaped tubes under column-flow conditions.