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Capillary Valve Effect on Drying of Porous Media
Published in Peng Xu, Agus P. Sasmito, Arun S. Mujumdar, Heat and Mass Transfer in Drying of Porous Media, 2020
R. Wu, C.Y. Zhao, E. Tsotsas, A. Kharaghani
To reveal the influence of the CVE on two-phase transport in porous media, a pore-scale investigation is necessary. It is nontrivial to capture experimentally the pore-scale events during two-phase transport in real porous materials since they are not only opaque but also have complex microstructures. An alternative is to use the pore network (PN) modeling approach. This approach has been widely used as an effective tool to understand the two-phase transport in porous media (Blunt, 2001; Joekar-Niasar and Hassanizadeh, 2012). In this method, the void space of a porous medium is conceptualized as a pore network composed of regular pores of various sizes. The two-phase transport in a PN is depicted by the prescribed rules. For instance, to simulate the capillary force–dominated two-phase flow in porous media using the PN model, the invasion percolation algorithm proposed by Wilkiinson and Willemsen (1983) has been widely used (Blunt et al., 1992; Knackstedt et al., 1998, 2001; Mani and Mohanty, 1999; Lopez et al., 2003; Araujo et al., 2005; Ceballos and Prat, 2013).
Influence of pore-network microstructure on the isothermal-drying performance of porous media
Published in Drying Technology, 2022
There are two major categories of methods dealing with problems involving drying dynamics of porous media, which are the continuum-based methods and the discrete methods. The continuum-based methods ignore the actual microstructures of the porous media and treat the porous media as continuous regions described by some volume-averaged properties.[4,5] On the other hand, the discrete methods capture the pore-level microstructures and conduct detailed study of mass and energy transport inside them. The pore-network (P-N) model[6] equipped with invasion-percolation (I-P) algorithm[7,8] is one of them. The original formulation of the algorithm showed a good agreement with the experiments on liquid-phase distribution, while failed to match the drying rates and drying times.[9,10] Further research observed the existence of liquid films along the corners of throats during the receding of the liquid phase during drying. And the addition of film effect to the original P-N model greatly improved its accuracy in predicting the drying-rates and drying-times.[11–13] Since then, more and more physics has been added onto the P-N model to improve its applicability and accuracy; such physics include the viscous effect,[14,15] the thermal effect,[16–18] and the more realistic ring structure among discrete corner films.[19] Based on the P-N model, techniques for coupling the lab-scale flow dynamics surrounding the drying porous media with the pore-scale drying dynamics inside such media were also developed.[20–22] Both lab-scale and pore-scale physical and geometrical factors influencing drying have been broadly studied,[23–26] in which, the experiments and numerical simulations of drying in dual-scale porous media showed that materials with dual-scale throats diameters, if arranged in layers, could yield some unique drying characteristics. Recent research has opened one to the idea that the drying performance of materials can be improved by designing optimum microstructures.[17,27–30]