Abstract
A model for non-Fickian moisture transfer in wood is presented. The model considers the transfer of water vapour separate from the transfer of bound water. These two components are linked by an equation describing the sorption on the cell wall level. Hereby, a formulation capable of describing known non-Fickian effects, including the effects of step size, absolute moisture content, and sample length, is achieved. The sorption curves predicted by the model are compared with experimental results and good agreement is found.
Réssumé
Un modèle pour le transfert non-Fickien d'humidité dans le bois est présenté. Le modèle considère le transfert de la vapeur d'au séparé pour le transfert de l'eau liée. Ces deux composants sont liés par une équation décrivant la sorption au niveau de mur de cellules. Par ceci, une formulation capable de décrire des effets non-Fickian connus, comprenant les effets de la taille d'étape, le contenu d'humidité absolu, et la longueur d'échantillon, est réalisée. Les courbes de sorption prévues par le modèle sont comparées aux résultats expérimentaux et une bonne concordance est trouvée.
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Abbreviations
- D :
-
Diffusion coefficient
- E :
-
Fractional weight increase
- h :
-
Sorption constant (kgm−3s−1Pa−1)
- j :
-
Flux (kgm−2s−1)
- m :
-
Moisture content (kg/kg)
- \(\dot m\) :
-
Sorption term (kgm−3s−1)
- p :
-
Pressure (Pa)
- r :
-
Relative humidity (RH)
- R :
-
Gas constant (8.31 Jmol−1K−1)
- T :
-
Temperature (K)
- w :
-
Moisure content (kgm−3)
- Φ:
-
Porosity
- σ:
-
Density (kgm−3)
- ξ:
-
Internal area/volume ration (m−1)
- τ:
-
Vapour diffusivity reduction factor
- a :
-
air
- eff :
-
effective
- g :
-
gas—vapour+air
- L :
-
longitudinal
- T :
-
tangential
- v :
-
vapour
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Krabbenhoft, K., Damkilde, L. A model for non-fickian moisture transfer in wood. Mat. Struct. 37, 615–622 (2004). https://doi.org/10.1007/BF02483291
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DOI: https://doi.org/10.1007/BF02483291