Influence of pore-network microstructure on the isothermal-drying performance of porous media

Abstract

Numerical experiments were conducted to investigate the influence of pore-level microstructure on the drying performance of porous media using pore network (P-N) models. The drying simulation based on the invasion-percolation (I-P) algorithm included the film effect, however the interaction with the outside flow-field was simplified using a constant-concentration vapor-diffusion layer. Three groups of experiments with progressive relationships are designed starting from some general rules learned from previous research, such as: (1) increasing the opening area; (2) making the big-throats penetrate into the inside of a pore network to form good transportation routes. Group 1 compared 7 one-side open $60\times 60$ planar P-N microstructures with the same liquid volume, different opening area and different transportation routes; Group 2 compared 4 one-side open $20\times 200$ planar P-N microstructures with the same liquid volume, different opening area, different transportation routes, and different cross-sectional throat shape; Group 3 compared 4 four-sides open $120\times 30$ planar P-N microstructures with the same liquid volume, the same opening area, but different transportation routes. All experiments demonstrated that large opening area and good transportation route are all beneficial to the quick-drying performance. However, the strength of different mechanisms influencing the drying performance changes with the pore network itself and the environmental conditions, including the P-N size, P-N aspect ratio, cross-sectional shape of throats, and environmental humidity. Accordingly, the optimum microstructure of quick-drying porous media changes with all these conditions. The final optimal design for a quick-drying microstructure can only be achieved by getting back to the fundamental pore-level dynamics which takes all the influencing mechanisms into account.

Keywords:

• Porous media
• microstructure
• drying
• quick drying performances
• pore-network model
• invasion-percolation algorithm
• film effect

Disclosure of Interest Statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Notes

1 For the square network under consideration, the north, south, east and west sides are respectively the top, bottom, right and left sides.

2 The randomly-selected time is when the bulk liquid in the first n number of throats dried out, so the physical time for each case is not the same.