Capillary pressure in softwoods

Spolek, Graig A.; Plumb, O. A.

doi:10.1007/bf00353471

Cited by 93 publications

(40 citation statements)

References 3 publications

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“…Also, as can be seen from Figure 4, the permeability properties drop close to zero at the saturation value of 0.1. This is due to failure of liquid transport by capillary action and this is no longer possible below the irreducible saturation level [23,24]. It has been found that the experimental detection of very low permeability is extremely difficult and it is generally taken as equal to zero in the drying process.…”

Section: One Dimensional Case Study and Validationmentioning

confidence: 99%

Combined heat and mass transfer for drying ceramic (shell) body

Harun¹,

Gethin²,

Lewis³

2008

The International Journal of Multiphysics

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Section: One Dimensional Case Study and Validationmentioning

confidence: 99%

Combined heat and mass transfer for drying ceramic (shell) body

Harun¹,

Gethin²,

Lewis³

2008

The International Journal of Multiphysics

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“…The determination of the relationship between water potential (q0, chemical potential (gt) or capillary pressure (PC) and solid wood moisture content (M) above the fiber z35 saturation point has been the object of several studies (Perem 1954;Penner 1963;Stone, Scallan 1967;Griffin 1977;Viktorin, Cermak 1977;Fortin 1979;Spolek, Plumb 1981;Choong, Tesoro 1989;Cloutier, Fortin 1991). The techniques generally used are the tension plate, the pressure plate, the pressure membrane and the centrifuge.…”

Section: Introductionmentioning

confidence: 99%

Effect of specimen structural orientation on the moisture content ? water potential relationship of wood

1995

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Summary The boundary desorption curve of the moisture content -water potential relationship of aspen sapwood was determined at 20 ~ by the tension plate and pressure membrane methods for three specimen structural orientations and four imposed water potential values. The results show that the relationship is independent of the wood structural direction considered. Also, they further demonstrate that the discrepancies observed in a previous study between the moisture content -water potential relationships obtained with specimens of different structural orientations were due to a lack of equilibrium.

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“…Secondly, this process stops at a well defined point (MC ~ 95 %) and is replaced by receding fronts instead. The "gradient free drying" has been experimentally observed (Wiberg and Morén 1999) and the transfer to receding fronts corresponds to the break-up of the continuous water phase (Stauffer and Aharony 1992) which has been named "irreducible saturation" in wood science (Spolek and Plumb 1981). Both these features are not easily modelled using a pure diffusion based approach.…”

Section: Modelling Drying Of Free Watermentioning

confidence: 99%

Fibre level modelling of free water behaviour during wood drying and wetting

Salin¹

2011

Maderas, Cienc. tecnol.

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Most drying simulation models describe the moisture migration in wood as a diffusion process, including free water flow at contents greater than the fibre saturation point. This means that wood is seen as a homogeneous material lacking internal structure. However, especially in softwood narrow sections, bordered pits, divide the free water phase into rather distinct units. It is thus quite clear that the flow of free water is governed by capillary forces and not by diffusion. A model has been developed that investigates how water filled units are emptied one by one in a drying process. Simulations with the model explain some experimentally seen features that cannot be obtained using solely diffusion type models.Water absorption by dried wood is generally assumed to be governed by capillary (surface tension) forces. An additional feature is that a considerable part of the bordered pits have been aspirated, i.e. closed, in the drying process and the number of possible flow paths is thus reduced. Thus the driving force for water flow is the capillary suction into the lumen. Modelling wood wetting by these principles also introduces some interesting specific features, such as a limit regarding the maximal achievable water saturation.In summary it is found that specific behaviour seen on a real macroscopic level originates from properties at the microscopic, fibre level. This clearly indicates that experience from fibre level models should be included in future drying and wetting simulation models. The work in this direction so far, has been promising.

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Capillary pressure in softwoods

Cited by 93 publications

References 3 publications

Combined heat and mass transfer for drying ceramic (shell) body

Combined heat and mass transfer for drying ceramic (shell) body

Effect of specimen structural orientation on the moisture content ? water potential relationship of wood

Fibre level modelling of free water behaviour during wood drying and wetting

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