Modelling by superimposition of basic parameters as a teaching tool

Modeling of multivariable problems using superimposition of basic parameters is a useful tool for teaching complicated cases based on fundamental analysis. It is shown here that the multivariable problem of mass transfer between gas and liquid phase in a column may be modeled using the basic equations of mass transfer derived for the single bubble. The proposed theoretical model determines the bubble size distribution in a dispersion in terms of gas holdup, a measurable quantity, and an intermediate value, namely, dynamic gas disengagement (DGD) profile. This profile could be obtained experimentally as a record of diminishing holdup after gas into the column is cut off. This approach involves many simplifying assumptions. However, the predicted value of mass transfer coefficient using this simplified model is in reasonable agreement with the values obtained using the known correlations in the literature. This shows that simplifying models are useful as well as meaningful tools for teaching multivariable problems before introducing the students to the correlations which do not have any apparent relation to the basic equations