(271g) A Simplified Mass Transfer Model for Liquid-Gas Systems with Enhanced Speed of Calculations for Determining Mass Transfer Rates

In this paper, a new generic computational mass transfer model is developed based on the penetration mass transfer model by defining new parameters, which are the infinite equilibrium concentration for the liquid and vapor phases. One merit of this approach is that it reduces the complexity of computations while still yielding high quality results. More importantly is, the new definitions represent the interactions between different bubble regimes by describing mass transfer in both the heterogeneous and homogeneous flow regimes.  Since this model is mathematically equivalent to Higbie’s penetration model, it can be applied to any system where Higbie’s penetration model can be applied, but can also be extended for use in bubble column systems involving turbulent fluid dynamics, mass transfer, and chemical reactions.

The simple model was developed and verified to represent experimental data or prior computational model results with high accuracy. Assumptions include constant gas volumes and pressures through idealized averages and assuming the bubbles reach equilibrium before leaving the liquid phase. We show the computational model assumption can be applied even in general situations where full equilibrium is not reached by using an analytically derived correction factor.  For example, in the case of a bubble column with a high Henry’s law constant, the assumption of the simple model is satisfied and the model shows that mass transfer is independent of the bubble size. However, in case of a bubble column with low Henry’s law constant, the assumption of reaching equilibrium is not satisfied, but the model with correction factor shows the mass transfer rate is areciprocal to the size of bubble with an order of around 1.5, which is supported by experimental data.

Finally, these fast computations of chemical equilibrium conditions, or pseudo-equilibrium states, can be useful when a physical system involves chemical reactions. When chemical reactions are involved, a reaction enhancment factor of mass transfer is needed and must be evaluated. However, with these equilibrium states or pseudo-equilibrium states, the necessity of the chemical reaction enhanced factor can be relaxed, since it implies that mass transfer can be described as one of the chemical reactions advanced to those equilibrium states or pseudo-equilibrium states using the same model.