Absorption and Desorption of Water along the Longitudinal Axis above and below the Fiber Saturation Point (Short Time of Absorption)

Mounji, H.; Kouali, M’hammed El; Vergnaud, J.M.

doi:10.1515/hfsg.1991.45.2.141

Cited by 16 publications

(15 citation statements)

References 6 publications

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“…The first method is followed in this paper. The factor of evaporation K was found to be the same for each direction (Droin-Josserand et al 1988;E1 Kouali, Vergnaud 1991;Mounji et al 1991).…”

Section: Diffusivity During the Stage Of Absorptionmentioning

confidence: 99%

Process of absorption and desorption of water in a wood board, with 3-dimensional transport beyond the FSP

1992

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Summary.The process of absorption of water in a piece of solid wood, as well as the following stage of desorption is studied, when the water content is beyond the fiber saturation point. A model based on a numerical method with finite differences is built and successfully tested. This model takes into account a 3-dimensional transport of water controlled by diffusion, with three principal axes of diffusion and three various principal diffusivities. The model is able to predict the kinetics of absorption or desorption when the three principal diffusivities are known, as well as the operational conditions.

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Section: Diffusivity During the Stage Of Absorptionmentioning

confidence: 99%

Process of absorption and desorption of water in a wood board, with 3-dimensional transport beyond the FSP

1992

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“…Mathematical and numerical models were successfully developed for adsorption and resorption of liquid water (Mounji andothers 1991, Kouali and.…”

Section: Introductionmentioning

confidence: 99%

Laboratory test for grouping tropical species for kiln drying

1995

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353Summary A system was developed for grouping tropical wood species for kiln drying based on similar estimated drying times. Six tropical species were subjected to drying and water soaking tests; variables were test temperature and specimen thickness. Soaking time, specimen thickness, and test temperature were used in an empirical model to predict drying times. The capability of the model to predict drying times was considered acceptable based on an adjusted coefficient of determination equal to 0.929 and an average error of 14 percent. The overall capability of the method proposed for grouping tropical hardwoods for drying is considered promising and worthy of further investigation. IntroductionDeforestation in the tropics, especially in the Amazonian region, has become a worldwide concern. The tropical forests of the world cover about 1.2 billion hectares, and more than 17 million hectares are destroyed every year (Reis 1990). Slash and burn agriculture and fuelwood account for 65 percent of tropical forest destruction (Lindell 1991). Increasing the economic value of the hundreds of species in the Amazonian forest could create an incentive for sustainable forest management. Improved drying can contribute to this goal by making lesser-used species more suitable for industrial processing.Industrial wood drying presently requires a large amount of wood of the same species to be practical. The heterogeneity of the Amazonian forest makes it almost impossible to continuously supply the amount of wood required for kiln drying with just one species. Use of such a heterogeneous wood supply requires a grouping system by which different species can be dried at the same time under the same drying schedule.The objective of this research was to develop a laboratory test for grouping tropical hardwoods for drying, based on similar drying times. BackgroundConsiderable attention has recently been given to the drying characteristics of tropical timbers. Many kiln schedules have been developed for tropical wood species (IBDF/DPq-LPF 1988, Longwood 1961. Nevertheless, little information is available on kiln drying of mixed tropical hardwood species (Simpson and Baah 1989).

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“…Many studies have been made on wood in contact either with moisture (Skaar 1958;Stamm 196o;Comstock 1963;Choong 1965;Moscher and Martin 1968;Droin et al, 19881;Droin et al, 19882;Droin et al, 19891;Droin et al, 19892) or with liquid water (Mounji et al, 19911;Mounji et al, 19912;Mounji et al, 19913;El Kouali and Vergnaud, 1991;E1 Kouali et al, 1991;Mounji and Vergnaud, 1992; E1 Kouali et al, 1992). In both these cases, the matter transfer through the wood can be successfully described by a diffusional process (Skaar 1958;Stamm 196o;Cornstock 1963;Choong 1965;Moscher and Martin, 1968;Droin et al, 1988 x, Droin et al, 19882;Droin et al, 19891;Droin et al, 19892;Mounji et al, 19911;Mounji et al, 19912;Mounji et al, 19913; E1 Kouali and Vergnaud, 1991;E1 Kouali et al, 1991E1 Kouali et al, , 1992Mounji and Vergnaud, 1992), in spite of the fact that the driving force may be the pressure gradient instead of a gradient of concentration (Bramhall 1976).…”

Section: Introductionmentioning

confidence: 99%

“…In both these cases, the matter transfer through the wood can be successfully described by a diffusional process (Skaar 1958;Stamm 196o;Cornstock 1963;Choong 1965;Moscher and Martin, 1968;Droin et al, 1988 x, Droin et al, 19882;Droin et al, 19891;Droin et al, 19892;Mounji et al, 19911;Mounji et al, 19912;Mounji et al, 19913; E1 Kouali and Vergnaud, 1991;E1 Kouali et al, 1991E1 Kouali et al, , 1992Mounji and Vergnaud, 1992), in spite of the fact that the driving force may be the pressure gradient instead of a gradient of concentration (Bramhall 1976). The main characteristics of the absorption process of moisture or water are the following: i) The wood is an anisotropic material with three main axes of diffusion, ii) The three main diffusivities are quite different, the longitudinal diffusivity being much larger than the other two.…”

Section: Introductionmentioning

confidence: 99%

“…The main characteristics of the absorption process of moisture or water are the following: i) The wood is an anisotropic material with three main axes of diffusion, ii) The three main diffusivities are quite different, the longitudinal diffusivity being much larger than the other two. iii) A rather low amount of water is absorbed when the wood is in contact with moisture, while a larger amount is absorbed when the wood is immersed in water (Mounji et al, 19911;Mounji et al, 19912;Mounji et al, 19913;E1 Kouali and Vergnaud, 1991;E1 Kouali et al, 1991E1 Kouali et al, , 1992Mounji and Vergnaud, 1992). iv) The diffusivities are concentration-dependent when the wood sample is in contact with moisture in air (Skaar 1958;Stamm 196o;Comstock 1963;Choong 1965;Moscher and Martin 1968;Droin et al, 19881, Droin et al, 19882;Droin et al, 19891;Droin et al, 19892).…”

Section: Introductionmentioning

confidence: 99%

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Process of absorption and desorption of methanol with a 3-dimensional transport through Picea wood

et al. 1994

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The process of absorption of methanol in liquid state by a wood sample, as well as the following step of desorption, is studied. A 3-dimensional transfer takes place within a cubic wood sample, this cube being cut in such a way that the sides of the cube are parallel with the longitudinal, radial and tangential axes of diffusion. A numerical model taking into account all the facts, e. g. diffusion within the solid and constant concentration on the surface during the stage of absorption, and diffusion within the solid and evaporation from the surface during the stage of desorption, is built and successfully tested. A pseudo-equilibrium of absorption is attained after an immersion time of about 3 hours in the liquid, and the whole amount of methanol is evaporated during the stage of desorption. The process can be described by a 3-dimensional diffusion with constant principal diffusivities.

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Absorption and Desorption of Water along the Longitudinal Axis above and below the Fiber Saturation Point (Short Time of Absorption)

Cited by 16 publications

References 6 publications

Process of absorption and desorption of water in a wood board, with 3-dimensional transport beyond the FSP

Process of absorption and desorption of water in a wood board, with 3-dimensional transport beyond the FSP

Laboratory test for grouping tropical species for kiln drying

Process of absorption and desorption of methanol with a 3-dimensional transport through Picea wood

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