A novel element for gas-liquid contact, a plate with rectangular windows was designed to enhance absorption process. Coexistence and interaction of wall-bounded films and confined free films named as twin-liquid films were observed on the plate. Volume of fluid (VOF) method was used to simulate its flow behavior. Flow phenomena such as flow around a step-in, jet impingement, varicose waves, and sinuous waves were observed. Different from thin films flow on an unperforated plate, larger mean velocity, thinner film thickness, more intensive capillary waves, and stronger vorticity on the free surfaces were detected inside the window, and the disturbances could propagate over the whole plate. Three-dimensional simulation results generally agreed with our experimental observations and further demonstrated complex wavy structures both inside and outside the window. The results would broaden traditional knowledge of liquid films flow and clarify the mechanism of mass transfer intensification for the plate with windows. (c) 2017 American Institute of Chemical Engineers AIChE J, 64: 1458-1468, 2018
