Diffusion coefficients of gases from the rate of approach to the steady state in thermal diffusion

1959 ◽  
Vol 2 (3) ◽  
pp. 264-270 ◽  
Author(s):  
S.C. Saxena ◽  
E.A. Mason
Keyword(s):  
Steady State ◽  
Thermal Diffusion ◽  
Diffusion Coefficients

scholarly journals Combined bound water and water vapour diffusion of Norway spruce and European beech in and between the principal anatomical directions

Holzforschung ◽  
2011 ◽  
Vol 65 (6) ◽  
pp. 819-828 ◽  
Author(s):  
Walter Sonderegger ◽  
Manuele Vecellio ◽  
Pascal Zwicker ◽  
Peter Niemz
Keyword(s):  
Diffusion Coefficient ◽  
Steady State ◽  
Water Vapour ◽  
Diffusion Coefficients ◽  
Bound Water ◽  
European Beech ◽  
Unsteady State ◽  
Water Vapour Diffusion ◽  
Vapour Diffusion ◽  
Water Vapour Resistance

Abstract The combined bound water and water vapour diffusion of wood is of great interest in the field of building physics. Due to swelling stresses, the steady-state-determined diffusion coefficient clearly differs from the unsteady-state-determined diffusion coefficient. In this study, both diffusion coefficients and the water vapour resistance factor of Norway spruce (Picea abies [L.] Karst.) and European beech (Fagus sylvatica L.) were investigated for the principal anatomical directions (radial, tangential and longitudinal) and in 15° steps between these directions. The values were determined with the cup method as the basic principle. The unsteady-state-determined diffusion coefficient is, independent of the direction, about half that of the steady-state-determined diffusion coefficient. Both diffusion coefficients are about two to three times higher for spruce than for beech. They are up to 12 times higher in the longitudinal direction than perpendicular to the grain for spruce, and up to 15 times higher for beech. With increasing moisture content, the diffusion coefficients exponentially increase. The water vapour resistance factor shows converse values to the diffusion coefficients.

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