A Method to Estimate the Accuracy of 1-D Flow Based Permeability Measuring Devices

Abstract

This paper presents a new experimental procedure for calibrating the permeability measuring 1-D flow set-up used routinely by the composites processing community using the liquid composite molding processes such as RTM and VARTM. A reference porous medium consisting of a bank of parallel cylindrical holes is created in an aluminum plate whose theoretical permeability is computed using the Hagen—Poiseuille flow equation and whose numerical permeability is estimated using Fluent©. It is observed that the deviation of the experimentally measured permeability from the theoretical as well as the numerical permeabilities increases with the flow rate for an injection set-up using a gear pump as well as a piston-cylinder pump. The cause of permeability deviation is traced to opening of a small gap above the rigid reference porous medium due to high pressures at higher flow rates. However no such deviation is observed while measuring the permeability of a fiber mat at different flow rates. So the proposed reference porous medium can calibrate a conventional 1-D flow based permeability measuring set-ups at low flow rates; the accuracy thus obtained can be extended to higher flow rates as well if permeability of a fiber mat can be shown to remain constant with the flow rate.