Modeling and Measurement of Macroscopic Flow Fields in Structured Packings

Corrugated structured packings feature strong preferential flow directions due to their structure of crossing triangular channels. This leads to good radial spreading but makes modelling a challenge. Detailed CFD calculations reflecting the exact packing structure are only feasible for small sections of packing. However, effects like large scale maldistribution and instabilities in the flow field can only be modelled, if the hydrodynamics of the entire column are taken into account. In the present study, the macroscopic flow field of an entire column is modelled and numerically calculated. The model is based on the elementary cell model by Mewes et al. (1999). It is extended to be used on anisotropic porous structures like corrugated structured packings in counter-current operation. For the elementary cell model, flow field variables (velocity, phase volume fraction, pressure, etc.) and packing properties (void fraction, pressure drop, momentum exerted on fluids, etc.) are averaged over the volume of a representative elementary cell. For the gas phase, measurements of the directional pressure drop are conducted and used to model the anisotropic gas flow resistance tensor. To model the liquid flow field, two liquid phases are modelled each representing laminar film flow along one preferential flow direction. The elementary cell model allows to determine the macroscopic flow field in columns of technical dimensions. In the present study, it is used to calculate the two-phase flow field under stationary, counter-current operating conditions below the loading point. The results are tested against X-ray radiographic measurements on a quasi two-dimensional segment of structured packing.