Dai, G. and Ahmet, K.
1999
8th International Conference on Durability of Building Materials and Components, Vancouver, Canada, May 28 - June 3, pp. 701-713
sorption model; timber moisture content, numerical analysis
| Although moisture is a leading cause of degradation in a range of building materials the transport mechanisms for adsorption and desorption are not well understood and mathematical modelling has been of limited success. This paper presents a mathematical model with numerical analysis by use of the method of finite differences. Mathematical analysis of moisture transmission with assumption of Newmann's boundary conditions was made. The model can be used to describe the process of adsorption and desorption of moisture in timber, where the transport of moisture follows the transverse direction of wood, with potential extension to the longitudinal direction also. The model makes it possible to attain the profiles of concentration of moisture developed throughout the sample. Data resulting from changes in relative humidity and collected by continuous monitoring by calibrated moisture sensors are compared against result from modeling. Good agreement has been observed over various conditions.
Cited ref
Ahmet, K. et al (1995) The moisture content of internal timber, Building Engineer, Vol.70, No.2, pp18-20
Ahmet, K. et al (1996) Standardisation of conductance-type timber moisture meters, Proc. 7 th International Conference on Durability of Building Materials and Components, Stockholm, Sweden, pp673-682
Ahmet, K and Dai, G. et al (1998) Experimental procedures for determining the equilibrium moisture content of twenty timber species. Forest Products Journal, Vol.48, No.11/12
Avramidis, S. and Siau, J (1987) An investigation of the external and internal resistance to moisture diffusion in wood. Wood Science and Technology, Vol.21, No.2, pp249-256
Babiak, M. (1995) Is Fick's law valid for the adsorption of water by wood? Wood Science and Technology, Vol.29, No.3, pp227-229
Crank, J. (1975) The mathematics of diffusion. 2nd Ed., Clarendon Press, Oxford, London, 346pp
Dai, G. and Ahmet, K (1998) Moisture monitoring system based on a remote moisture sensor. Proc. CIB World Building Congress, Gavle, Sweden, Vol.1, pp107-114 Hunter, A. (1996) Wood drying and Fick's second law. Wood Science and Technology, Vol.30, No.5, pp355-359
Liu, J. et al (1994) Simulation of heat and and moisture transfer in wood during drying under constant ambient conditions. Holzforschung, Vol.48, No.3, pp236-240
Nakano, T. (1995) Note on a formulation of a water adsorption process of wood Wood Science and Technology, Vol.29, No.3, pp231-233
Pang, S. (1996) Moisture content gradient in a softwood board during drying: simulation from a 2-D model and measurement. Wood Science and Technology, Vol.30, No.2, pp165-178
Plumb, O.A. et al (1985) Heat and mass transfer in wood during drying International Journal of Heat and Mass Transfer. Vol.28, No.9, pp1669- 1678
Siau, J.F. (1984) Transport processes in wood. Springer-Verlag. New York, NY 245pp
Simpson, W.T. (1993) Determination and use of moisture diffusion coefficient to characterise drying of northern red ork. Wood Science and Technology, Vol 27, pp409-420
Skaar, C (1988) Wood-water relations. Springer-Verlag. New York, NY. 283 pp
Stanish, M.A. et al (1986) A mathematical model of drying for hygroscopic porous media. AICHE. J., Vol.32, No. 8, pp1301-1311
Tong, Y. and Suchsland, O. (1993) Application of finite element analysis to panel warping. Holz Roh-Werkst. Vol.51, No.1, pp55-57
TRADA (1998) Benchmark diagnostic data on timber moisture content, Report number RTT/G00181/1, TRADA, High Wycombe, Bucks. UK TRADA (1991) Moisture in timber, TRADA Wood Information, Section 4, Sheet 14 |