Summary
A model for the isothermal transport of bound water through the cell wall of wood is developed, based on the assumption that the driving force for moisture movement is the gradient of “spreading” pressure ϕ, as first proposed by Babbitt (1950). This pressure is a surface phenomenon, derivable from the surface sorption theory of Dent (1977), a modification of the BET sorption theory. The force resisting moisture transport is assumed to be inversely proportional to moisture content and directly proportional to the equivalent viscosity of the sorbed water, calculated to be orders of magnitude larger than that of free water. The coefficients normally used to describe isothermal moisture transport in wood are derived from the model, and their predicted behavior as functions of the relative vapor pressure h of the cell wall are described graphically. An attempt is made to calculate a quantitative magnitude for the diffusion coefficient D, based on an assumed relationship between viscosity and the activation energy for water diffusion.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
Babbitt, J. D. 1950: On the differential equations of diffusion. Can. J. Res., Sect. A. 28: 449–474
Babbitt, J. D. 1951: On the diffusion of adsorbed gases through solids. Can. J. Phys. 29: 437–446
Babbitt, J. D. 1958: Diffusion of adsorbed molecules. Nature 182: 201–202
Bramhall G. 1979: Sorption diffusion in wood. Wood Sci. 12 (1): 3–13
Brunauer, S.; Emmett, P. H.; Teller, E. 1938: Adsorption of gases in multimolecular layers. J. Am. Chem. Soc. 60: 309–319
Choong, E. T. 1963: Movement of moisture through a softwood in the hygroscopic range. For. Prod. J. 13 (11): 489–498
Dent, R. W. 1977: A multilayer theory for gas sorption. Part I: Sorption of a single gas. Text. Res. J. 47: 145–152
Jost, W. 1960: Diffusion in solids, liquids, gases. Third printing, with addendum. Academic Press: New York
Okoh, K. I. A.; Skaar, C. 1980: Moisture sorption isotherms of the wood and inner bark of 10 southern U.S. hardwoods. Wood and Fiber 12: 98–111
Skaar, C.; Siau, J. F. 1981: Thermal diffusion of bound water in wood. Wood Sci. Technol. 15: 105–112
Stamm, A. J. 1946: Passage of liquids, vapors and dissolved materials through softwoods. U. S. Dept. Agr. Tech. Bull. 929: 1–80
Stamm, A. J. 1959: Bound-water diffusion into wood in the fiber direction. For. Prod. J. 9 (1): 27–32
Stamm, A. J. 1977: Monomolecular adsorption and crystallite diameters of cellulose from structural and adsorption considerations. Wood Sci. Technol. 11: 39–49
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Skaar, C., Babiak, M. A model for bound-water transport in wood. Wood Sci.Technol. 16, 123–138 (1982). https://doi.org/10.1007/BF00351098
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00351098