Spontaneous imbibition of liquid in glass fiber wicks,Part II: Validation of a diffuse‐front model

In Part I (Zarandi MAF, Pillai KM. Spontaneous Imbibition of Liquids in Glass‐Fiber Wicks. Part I: Usefulness of a Sharp‐Front Approach. AIChE J, 64: 294–305, 2018), a model based on sharp liquid‐front was proposed where a good match with the experimental data was achieved. However, the model failed to account for partial saturations in the wicks. Here, Richard's equation to predict liquid saturation is tried where the equation is solved numerically in 3D using COMSOL and analytically in 1D using Mathematica for glass‐fiber wicks after treating them as transversely‐isotropic porous media. As a novel contribution, relative permeability and capillary pressure are determined directly from pore‐scale simulations in wick microstructure using the state‐of‐the‐art software GeoDict. The saturation along the wick length is determined experimentally through a new liquid‐N₂ based freezing technique. After including the gravity effect, good agreements between the numerical/analytical predictions and experimental results are achieved in saturation distributions. We also validated the Richard's equation based model while predicting absorbed liquid‐mass into the wick as function of time. © 2017 American Institute of Chemical Engineers AIChE J, 63: 306–315, 2018