Assessment of the Pore Diameter Measured in Gas-Liquid Displacement Porometry: Effect of the Capillary Constant

Abstract

Determining pore sizes of porous media accurately is essential for many reasons. The standard ASTM F316 describing calculations used in gas-liquid displacement (GLD) porometry includes a factor B or a capillary constant. The standard does not explain the nature of this factor and the reasons for using its value. This work aims to investigate the capillary constant and to understand its meaning and applicability in calculating the pore diameter. Another goal is to assess the pore diameter measured in GLD porometry by comparing it with pore diameters measured with image analysis and cut point test methods. Seven filter media samples with as simple a structure as possible were analyzed. An investigation of the capillary constant revealed at least five different approaches, of which all are by no means applied for the calculations of pore size. Using the approach described in standard ASTM F316 to adjust the values obtained by GLD porometry was found unsuitable for the simply structured samples studied in this work. This work shows that the pore diameters measured by GLD porometry are most comparable with the other studied techniques when using Silwick as the wetting liquid. The raw data of bubble point pore and mean flow pore diameters measured by GLD porometry are similar to the largest pore sizes and mean pore diameters measured by image analysis and cut point test methods. This, in turn, confirms the absence of the need to use any constants for calculating the pore diameters for the samples studied in this work.