Journal of the Korean Wood Science and Technology

The Korean Society of Wood Science & Technology (한국목재공학회)
권호 표지

Estimation of Moisture Diffusivity during Absorption by Boltzmann Transformation Method

Boltzmann법에 의한 목재 흡수시 확산계수 추정

  • Kang, Wook (Department of Forest Products and Technology, College of Agriculture, Chonnam National University) ;
  • Chung, Woo Yang (Department of Forest Products and Technology, College of Agriculture, Chonnam National University)
  • 강욱 (전남대학교 농업생명과학대학 임산공학과) ;
  • 정우양 (전남대학교 농업생명과학대학 임산공학과)
  • Received : 2008.07.16
  • Accepted : 2008.10.08
  • Published : 2009.01.25
Download PDF
⟨ Previous Next ⟩

Abstract

Although the exterior wood such as column may frequently contact with liquid water, little work has been found to measure liquid water absorption in wood. To investigate the moisture diffusivity of wood in the longitudinal direction including bound water and free water movement, liquid water absorption test was conducted at the room temperature. The order of magnitude for absorption coefficient and diffusivity was Japanese elm, horn beam, hemlock, spruce, radiata pine, and painted maple. The Boltzmann transformation method was used to determine the diffusivity from measured moisture content distributions in the absorption test. The shape of the curve representing the dependence of diffusivity with moisture content was similar in test samples. The diffusivity decreased with increasing moisture content until around the fiber saturation point and then increased at the nonhygroscopic region, which ranged from $10^{-10}$ to $10^{-7}m^2/s$.

외장용 기둥재는 년중 사용환경에서 액상수와 직접 접촉할 수가 있으나, 이에 대한 연구는 그다지 많지 않다. 목재의 섬유방향에서 결합수와 자유수 확산계수를 포함한 수분확산계수를 측정하기 위해 상온에서 흡수실험을 실시하였다. 흡수성은 느릅나무, 까치박달나무, 헴록, 가문비나무, 라디에타 소나무, 고로쇠나무 순으로 크게 나타났다. Boltzmann 변환법으로 구한 확산계수는 저함수율에서 섬유포화점 부근까지 감소하다가 최대함수율 부근에서 급격히 증가하는 경향을 나타내었다. 함수율 변화에 따른 확산계수는 $10^{-10}{\sim}10^{-7}m^2/s$ 정도의 값을 나타내었다.

Keywords

Acknowledgement

Supported by : 국립문화재보존연구소

References

  1. Couture, F., W. Jomma, and J. R. Puiggali. 1996. Relative permeability relations : a key factor for a drying model. Transport in Porous Media 23: 303-335. https://doi.org/10.1007/BF00167101
  2. Janz, M. 1997. Methods of measuring the moisture diffusivityat high moisture levels. TVBM-3076. Univ. of Lund, Sweden.
  3. Kang, W., Y. H. Lee, W. Y. Chung, and H. L. Xu. 2008. Parameter estimation of mositure transfer in wood. SET 2008 7th International Conference on Sustainable Energy Technologies. Seoul, Korea. 24-27 August. pp. 2119-2126.
  4. Kang, W., W. Y. Chung, C. D. Eom, and H. M. Yeo. 2008. Some considerations in heterogeneous nonisothermal transport models for wood: Numerical study. J. Wood Sci. 54: 267-277. https://doi.org/10.1007/s10086-007-0938-0
  5. Kang, W., C. W. Kang, W. Y. Chung, C. D. Eom, and H. M. Yeo. 2007. The effect of openings on combined bound water and water vapor diffusion in wood : Revisited. J. Wood Sci. (accepted). https://doi.org/10.1007/s10086-008-0965-5
  6. Kang, W. and Y. H. Lee. 2006. Control volume finite element method for wood drying. Proceedings of the National Institute for Mathematical Sciences. National Institute for Mathematical Sciences. 1(8): 29-40.
  7. Koponen, H. 1987. Moisture diffusion coefficients of wood. Drying 87, Hemisphere Publishing Company.
  8. Kumaran, M. K. 1999. Moisture diffusivity of building materials from water absorption measurements. J. Thermal Env. & Bldg. Sci. 22: 349-355. https://doi.org/10.1177/109719639902200409
  9. Lee, Y. H., W. Kang, and W. Y. Chung. 2007. Numerical solution for wood drying on one-dimensional grid. Journal of the Korean Society for Industrial and Applied Mathematics. 11(1): 95-105.
  10. Moyne, C. and P. Perre. 1991. Process related to drying: Part I, theoretical model. Drying Technology 9(5): 1135-1152. https://doi.org/10.1080/07373939108916746
  11. Mukhopadhyaya, P., K. Kumaran, and N. Nordmandin. 2002. Effect of surface temperature on water absorption coefficient of building materials. J. Thermal Env. & Bldg. Sci. 26: 179-195. https://doi.org/10.1177/0075424202026002974
  12. Perre, P., M. Moser, and M. Martin. 1993. Advances in transport phenomena during convective drying with superheated steam and moist air. Int. J. Heat Mass. Transfer 36(11): 2725-2746. https://doi.org/10.1016/0017-9310(93)90093-L
  13. Perre, P. and I. W. Turner. 1999. A 3-D version of TransPore: a comprehensive heat and mass transfer computational model for simulating the drying of porous media. Int. J. Heat Mass. Transfer 42: 4501-4521. https://doi.org/10.1016/S0017-9310(99)00098-8
  14. Perre, P. and I. W. Turner. 2001. Determination of the material property variations cross the growth ring of softwood for use in a heterogeneous drying model. Part 2. Use of homogenization to predict bound liquid diffusivity and thermal conductivity. Holzforschung 55: 417-425. https://doi.org/10.1515/HF.2001.069
  15. Roels, S. 2000. Modeling unsaturated moisture transport in heterogeneous limestone. PhD Thesis, Catholic Univ. of Leuven, Belgium.
  16. Rosen, H. N. 1974. Penetration of water into hardwoods. Wood and Fiber. 5(4): 275-287.
  17. Turner, I. W. and P. Perre. 1996. Mathematical model and numerical techniques in drying technology : A synopsis of the strategies and efficient resolution techniques for modeling and numerically simulating the drying process. pp. 1-82. Marcel Dekker Inc.
  18. 김정환, 이원희. 2002. 고온수증기 처리에 의한 낙엽송재의 물성변화. 목재공학 30(4): 1-7.
  19. 이명재, 이동흡, 이현미, 손동원. 2005. 초음파 침지처리재에 의한 목재방부제의 주입성. 목재공학 33(3): 64-71.