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Wood Science and Technology

, Volume 31, Issue 6, pp 415–422 | Cite as

An experimental assessment of driving forces for drying in hardwoods

  • T. A. G. Langrish
  • N. Bohm
Originals

Summary

An investigation has been carried out into whether the internal moisture movement inside Australian hardwood timber is best described by a diffusion model with driving forces based on gradients in moisture content or in partial pressure of water vapour. Experimental data from two sets of drying schedules applied to timber from three species of Australian hardwoods (yellow stringybark, spotted gum and ironbark) reported in Langrish et al. (1997) have been used to assess the use of the two driving forces, and the standard error has been used as the criterion for goodness of fit. Moisture-content driving forces have fitted the data better than a model based on vapour-pressure driving forces alone. The use of moisture-content driving forces with diffusion parameters obtained from data from one drying schedule is also better in predicting the drying behaviour with another schedule than vapour-pressure driving forces for yellow stringybark and ironbark. These results may be due to the complexity of the moisture-movement process through timber, with more than one moisture-transport mechanism being active, so that the use of only one driving force for moisture movement is at best only an approximation to the true behaviour.

Keywords

Experimental Data Standard Error Water Vapour Partial Pressure Timber 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Symbols

D

diffusion coefficient, m2 s−1 (moisture-content gradient), m3 s kg−1 (vapour-pressure gradient)

De

activation energy, K

Dr

pre-exponential factor m2 s−1 (moisture-content gradient), m3 kg−1 (vapour-pressure gradient)

J

mass flux of water divided by density, m s−1

t

time, s

x

position, m

X

moisture content, kg kg−1

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References

  1. Bramhall, G. 1995: Diffusion and the drying of wood. Wood Sci. Technol. 29: 209–215Google Scholar
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Copyright information

© Springer-Verlag 1997

Authors and Affiliations

  • T. A. G. Langrish
    • 1
  • N. Bohm
    • 1
  1. 1.Department of Chemical EngineeringUniversity of SydneyN.S.W.Australia

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