This paper presents the residence time profiles for single-pass and two-pass liquid flows by tracer technique for a water/air system in an experimental semicircular sieve tray of 2 meters in diameter. Analysis of residence time profiles indicates complicated flow pattern for single-pass flow. For two-pass liquid

similar flow pattern is observed from the residence profiles on center downcomer tray

while relatively uniform convergent flow is found on side downcomer tray. A mathematical model based on residence time profiles for single-pass tray is presented to compute the concentration profiles and the enhancement ratio

i. e. the ratio of the Murphree tray efficiency to the point efficiency. The average deviation between the predicted and the experimental tray efficiency found in literature is less in present model than the other existing models. Similar modeling for two-pass liquid flow is also presented including central downcomer and side downcomer tray

the proposed model agrees closely with recently published results. Finally

this paper introduces two kinds of new constructions on the experimental tray

which have shown successful improvement on the uniformity of liquid flow. These constructions are simple

practical and capable of increasing tray efficiency considerably.