Simulation of coalescence, break-up and mass transfer in a gas–liquid stirred tank with CQMOM

Abstract

In this work oxygen mass transfer in a turbulent air–water stirred tank is investigated. A multivariate population balance model is coupled with the Eulerian multi-fluid approach to describe the spatial and temporal evolution of the bubble size and composition distributions. For the numerical solution of the population balance model the conditional quadrature method of moments is employed and implemented through user-defined scalars and functions in the computational fluid dynamics code ANSYS/Fluent 12. The approach is validated by comparing model predictions with experiments (from the literature) conducted in an air–water stirred tank equipped with a Rushton turbine and a porous sparger. First predictions are compared with the experimentally measured mean Sauter diameter. The comparison highlights that the modeling approach is capable of predicting the main feature of the system. Then oxygen mass transfer is simulated and predictions for the oxygen accumulation in water are validated against experiments. Also for this comparison good agreement is found.