Numerical simulation of transport processes in multiphase systems

The present study is aimed at developing numerical techniques and theories for understanding transport processes in multiphase systems. In particular, the emphasis is on extending the current analytical framework, which is largely concerned with the study of single-phase fluid flow through monodisperse suspensions, to treat more complex systems. This is done by examining three problems.; The first is the study of countercurrent gas-liquid flow through a fixed bed of spherical particles The gas pressure drop and the liquid holdup are obtained at various volume fractions of the spheres and the gas and liquid flow rates by rigorous computations. These computations are used, in turn, to assess the existing theories and to modify them.; The second study is concerned with mass transfer processes in hollow fiber contactors modeled as shell and tube exchangers. Shell side mass transfer and Taylor dispersion coefficients are determined as functions of area fraction of tubes for random and periodic arrangement of tubes. It is shown that the mass transfer coefficients for random arrangements can be drastically lower than those for periodic arrangements. A theory is developed to explain this result of numerical analysis and the results of computations are compared with those obtained experimentally by previous investigators.; Finally, the third study is concerned with the determination of hydrodynamic transport properties of bidisperse suspensions. The existing theories for determining the coefficients for monodisperse suspensions are modified and the predictions of the modified theories are shown to agree well with the results of numerical computations.