A Method to Measure the Permeability of Dry Fiber Mats


  • Patrik Pettersson
  • T. Staffan Lundström
  • Tomas Wikström


Medium density fiberboard, gas permeability, anisotropic permeability, experimental validation, porous flow


Close to the finalization of the medium density fiberboard process, a fairly thick bed of loosely entangled fibers is compressed in a belt-press to often less than a tenth of its original unstressed thickness. This single unit operation is very important to consider when the manufacturing process of the boards is to be optimized. Despite this, there is a lack of knowledge of the interaction between the fiber mat strength and how the fluid flows through it, i.e. de-aeration. Thus, it is of greatest importance to find reliable methods for studying this stage of the manufacturing process. Following this quest, a method is developed with which the gas permeability of fiber mats can be measured. The method offers the potential to measure the permeability at different flow rates and thus at arbitrary pressure gradients through the material. The method is successfully validated with a porous reference material consisting of polymer spheres, and it is shown that the flow follows Darcy's law at the flow rates of interest. Finally, the method is demonstrated by a presentation of permeability measurements on fiber mats consisting of spruce fibers.


Bear, J. 1972. Dynamics of fluids in porous media. American Elsevier, New York, NY.nBelkacemi, K., and A. D. Broadbent. 1999. Air flow through textiles at high differential pressures. Textile Res. J.69(1):52-58.nBouazza, A., and T. Vangpaisal. 2003. An apparatus to measure gas permeability of geosynthetic clay liners. Geotextiles and Geomembranes21:85-101.nBuntain, M. J., and S. Bickerton. 2003. Compression flow permeability measurement: A continuous technique, Elsevier Science Composite, Auckland, New Zealand. Part A 34:445-457.nDullien, F. A. L. 1992. Porous media: Fluid transport and pore structure, Academic Press, San Diego, CAnHåkanson, J. M., S. Toll, and T. S. Lundström. 2005. Liquid permeability of anisotropic fibre webs. Textile Res. J.75(4):304-311.nKoponen, A. 1998. Simulations of fluid flow in porous media by lattice-gas and lattice-boltzman method. Research Report 5. Department of Physics, University of Jyväskylä, Finland.nLu, W. M., Y. P. Huang, and K. J. Hwang. 1998. Methods to determine the relationship between cake properties and solid compressive pressure. Tamsui. Elsevier. Separation and Purification Technol.13 1998:9-23.nLundström, T. S., B. R. Gebart, and E. Sandlund. 1999. In-plane permeability measurements on fibre reinforcements by the multi-cavity parallel flow technique. Polymer Composites20:146-154.nLundström, T. S., R. Stenberg, R. Bergström, H. Partanen, and P. A. Birkeland. 2000. In-plane permeability measurements: A Nordic round-robin study. Composites: Part A31:29-43.nRumpf, H., and A. R. Gupte. 1971. Chem. Ing. Tech.43(6):367-375.nScheidegger, A. E. 1972. The physics of flow through porous media, University of Toronto Press, Toronto, Canada.nSullivan, R. R., and K. L. Hertel. 1940. The flow of air through porous media, J. Appl. Physics11:761-765.nThompson, P. A. 1972. Compressible-fluid dynamics. Mcgraw-Hill Book Company, New York, NY.nVomhoff, H., and B. Norman. 2001. Method for the investigation of the dynamic compressibility of wet fibre networks. Nordic Pulp Paper Res. J.16(1):57-62.nWikström, T., and A. Rasmuson. 1998. Yield stress of pulp suspensions. Nordic Pulp Paper Res. J.13:243-250.nWhitaker, S. 1996. The Forchheimer Equation: A theoretical development. Transport in Porous Media25:27-61.nZhu, S., H. R. Pelton, and K. Collver. 1995. Mechanistic modelling of fluid permeation through compressible fiber beds. Chemical Eng. Sci.50(22):3557-3572.n






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