Moisture flux determination in wood during drying above fibre saturation point using CT-scanning and digital image processing

Wiberg, Pär; Morén, Tom

doi:10.1007/s001070050029

Cited by 47 publications

(28 citation statements)

References 8 publications

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“…Most frequently, X-ray transmission measurements are applied. This approach includes evaluating computed tomographies (CTs) (Wiberg and Moré n 1999;Alkan et al 2007;Scheepers et al 2007) and X-ray densitometry (Baettig et al 2006;Cai 2008;Watanabe et al 2008). Nuclear magnetic resonance (NMR) is also a promising method in this context (Merela et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Non-destructive determination and quantification of diffusion processes in wood by means of neutron imaging

Mannes¹,

Sonderegger²,

Hering³

et al. 2009

HFSG

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Diffusion processes in samples of European beech (Fagus sylvatica L.) and Norway spruce (Picea abies wL.x Karst.) were determined and quantified by means of neutron imaging (NI). The experiments were carried out at the neutron imaging facility NEUTRA at the Paul Scherrer Institute in Villigen (Switzerland) using a thermal neutron spectrum. NI is a non-destructive and non-invasive testing method with a very high sensitivity for hydrogen and thus water. Within the scope of this study, diffusion processes in the longitudinal direction were ascertained for solid wood samples exposed to a differentiating climate (dry side/wet side). With NI it was possible to determine the local distribution and consequently the total amount of water absorbed by the samples. The calculated values scarcely differ from those ascertained by weighing (F3%). The method yields profiles of the water content over the whole sample, thus allowing the local and temporal resolution of diffusion processes within the sample in the main transport direction (longitudinal). On the basis of these profiles, it was possible to calculate the diffusion coefficients along the fibre direction according to Fick's second law.

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Section: Introductionmentioning

confidence: 99%

Non-destructive determination and quantification of diffusion processes in wood by means of neutron imaging

Mannes¹,

Sonderegger²,

Hering³

et al. 2009

HFSG

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“…Despite this the estimate followed the average moisture content closely enough to validate the prediction model. In previous wood drying research it has been shown that the wetline remains close to the surface for a large part of the drying process (Wiberg and Morén 1999). This phenomenon has been shown to occur in other wood species as well.…”

Section: Resultsmentioning

confidence: 70%

“…Even though the surface moisture content during drying is important to the final product quality, there has thus far not been a method to measure surface moisture content industrially. There have been academic examples of measuring surface moisture content measurement on small samples with near infrared (NIR), magnetic resonance and X-ray computed tomography scanning (Baettig et al 2006, Rosenkilde and Glover 2002, Watanabe et al 2011, Watanabe et al 2013, Wiberg and Morén 1999. Electrical resistivity has also been used (Yamamoto et al 2013).…”

Section: Introductionmentioning

confidence: 99%

A method to estimate wood surface moisture content during drying

Scheepers

Wiberg²,

Johansson

2017

Maderas, Cienc. tecnol.

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A method to estimate the surface moisture content below the fibre saturation point that is a function of the surface temperature, wet-and dry bulb temperatures, equilibrium moisture content, and fibre saturation point was evaluated. The method is based on the premise that the surface temperature is solely influenced by the surface moisture content and the climate that the surface is exposed to. The prediction model contends that the surface moisture content is equal to the fibre saturation point when the surface temperature is equal to the wet bulb temperature, and equal to the equilibrium moisture content when the surface temperature is equal to the dry bulb temperature, with a linear interpolation between those two points. The model thus predicts that the average moisture content of a thin piece of veneer can be predicted with fairly good accuracy. Also, when drying boards in a fast changing climate, e.g. fan reversals in industrial kilns, the surface temperature and surface moisture content should change as abruptly as the climate does. Additionally, the surface moisture content should correlate to the known drying phases, with a consistently high surface moisture content during the capillary phase when the wet line is close to the surface, and a quickly decreasing surface moisture content when the wet line moves into the wood during the transition to the diffusion phase. The prediction model was tested in these three scenarios and the results suggest that the basic premise is reasonable, and that the method is useful for surface moisture content estimation.

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“…By its ability to focus on water only, NMR imaging (Deurer et al 2002, Almeida et al 2008) is certainly more adapted for this purpose than X-ray tomography (Wiberg and Morén 1999).…”

Section: Discussionmentioning

confidence: 99%

A mesoscopic drying model applied to the growth rings of softwood: mesh generation and simulation results

Perré

Turner

2008

Maderas, Cienc. tecnol.

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A mesoscopic drying model that enables the drying simulation of quartersawn and fl atsawn wood sections consisting of several growth rings is presented. The procedure to generate the virtual board description directly from real sample images is also described. This virtual structure accommodates the prominent sample features, including its geometrical and physical properties, together with the density and structural variation across the growth rings. We give a synopsis of the sophisticated techniques developed specifi cally to generate this virtual description and exhibit the fi nal computational meshes produced by the software for quartersawn and fl atsawn sections. Low temperature drying simulations are then performed for both heterogenous and homogeneous model variants using these virtual descriptions and comparisons are made of the resulting MC fi eld evolution. A highlight of these comparisons is that the heterogeneous model captures realistic drying effects, including the fast drying of earlywood and the late removal of liquid water in latewood. In comparing the drying of quartersawn and fl atsawn boards we conclude that the effect of the heterogeneous nature of the MC fi elds is diminished somewhat when considering the fl atsawn section over the quartersawn section.

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Moisture flux determination in wood during drying above fibre saturation point using CT-scanning and digital image processing

Cited by 47 publications

References 8 publications

Non-destructive determination and quantification of diffusion processes in wood by means of neutron imaging

Non-destructive determination and quantification of diffusion processes in wood by means of neutron imaging

A method to estimate wood surface moisture content during drying

A mesoscopic drying model applied to the growth rings of softwood: mesh generation and simulation results

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