The flow patterns and hydraulics of gas-liquid flow on a commercial scale distillation tray is of great importance in determining the tray efficiency. Based on experimental data

a new correlation of average gas hold-up was fitted and built in the inter-phase momentum transfer source for CFD simulations. The simulations of combined directed valve trays of 1.2 m air-water system were carried out by Fluent

a commercial CFD software

and the flow pattern characteristics was investigated. The clear liquid height determined from CFD simulations was in good agreement with the predicted results calculated from the correlation in this work

which proved the validity of simulations. Non-ideal flow of liquid phase on the trays was quantified by the backflow volume ratio T

the ratio of backflow volume to total grid volume. The time-averaged values of the backflow volume ratio (Tav) of 3 tray patterns with different arrangements of trapezoidal and rectangular directed valves were calculated respectively. The results showed that the different arrangements of two kinds of valves had remarkable influence on volume fraction of backflow. By reasonable arrangement

Tav could reduce from 22.0% to 19.4% with the decreased backflow volume by 11.8% compared to the industrial tray. This study was expected to provide a guidance for the tray design and optimization.