A new mathematical model of mixing pool type is proposed for simulating the fluid flow and masstransfer behavior on a large tray.In the proposed model,the whole tray is divided into a number ofsquare (or rectangular)compartments or mixing pools,each of which is assigned to have adjustableflow and baekmixing in both z (along the main flow path) and w(perpendicular to the main flow path)directions.The chief features of present model are: (1) It is two dimensional model instead of usualone dimensional so that more complicated actual flowing condition obtained from hydrodynamic studyon a large tray can be closely simulated by adjusting the flow among mixing pools in both z and wdirections.(2) Since backmixing is taken into account,the number of mixing pools on a tray is fixedinstead of varied as in conventional mixing pool model; thus,the application of matrix computation ispossible.(3) The present model can be reduced to other tray models depending on the number of mixingpools to be chosen in each direction.The application of present model to predict the liquid phase concentration profiles and Murphreeefficiency enhancement on a large tray with complicated flow pattern and velocity distribution as we-observe in our experimental study are demonstrated.The effects of liquid flow rate,nonuniform veloc-.ity field,directional splashing and subsidiary flow are also investigated and discussed. A new mathematical model of mixing pool type is proposed for simulating the fluid flow and masstransfer behavior on a large tray. In the proposed model, the whole tray is divided into a number of square (or rectangular) compartments or mixing pools, each of which is assigned to have adjustableflow and baekmixing in both z (along the main flow path) and w (perpendicular to the main flow path) directions.The chief features of present models are: (1) It is two dimensional model instead of usualone dimensional so that more complicated actually flowing condition obtained from hydrodynamic studyon a large tray can be closely simulated by adjusting the flow among mixing pools in both z and wdirections. (2) Since backmixing is taken into account, the number of mixing pools on a tray is fixedinstead of varied as in conventional mixing pool model; thus, the application of matrix computation ispossible. (3) The present model can be reduced to other tray models depending on the number of mixing points n in each direction. The application of present model to predict the liquid phase concentration profiles and Murphreeefficiency enhancement on a large tray with complicated flow pattern and velocity distribution as we-observe in our experimental study is demonstrated. effects. liquid flow rate, nonuniform veloc-.ity field, directional splashing and subsidiary flow are also investigated and discussed.