Pore Network Drying Model for Particle Aggregates: Assessment by X-Ray Microtomography

Abstract

Convective drying of disordered glass bead packings has been investigated both experimentally and numerically. X-ray microtomography (XMT) and image analysis techniques have been used to determine the three-dimensional spatial distribution of the liquid and solid phases at the pore scale within the wet particle aggregates. The evolution of the liquid distribution in the aggregate has been tracked during the drying process. Particle center coordinates and radii have been extracted from the X-ray images using binarization and segmentation techniques. Based on this geometric data for a real aggregate, a pore network approximation of the pore space has been generated from a Voronoi tessellation about particle centers by designating Voronoi edges as interconnected cylindrical pores with radii computed from the distance between neighboring particles. This three-dimensional irregular pore network takes into account both the geometrical and topological characteristics (pore size distribution and connectivity) of the actual pore space. Drying simulations have been carried out for the pore networks obtained from the XMT and results are presented as phase distributions and moisture profiles. The simulated liquid phase distributions are in qualitative agreement with the experimental result, which indicates that pore network models are suited to describe the drying of dense particle aggregates at the pore scale.

Keywords:

• Convective drying
• Liquid distribution
• Particle aggregates
• Pore-scale simulation
• X-ray microtomography

ACKNOWLEDGMENTS

This work was financed by the German Research Foundation (DFG) in the frame of Graduate School GRK 1554 “Micro-Macro-Interaction in Structured Media and Particulate Systems.” The X-ray tomography device used in this study was financed by the EFRD (European Fund for Regional Development) in project no. 121108002.