scholarly journals Water Vapour Sorption and Moisture Transport in and Across Fibre Direction of Wood

2021 ◽  
Author(s):  
Alexander Murr
Keyword(s):  
Relative Humidity ◽  
Water Vapour ◽  
Sorption Kinetics ◽  
Sample Thickness ◽  
Fibre Direction ◽  
Transient Conditions ◽  
Water Vapour Sorption ◽  
Vapour Sorption ◽  
Water Vapour Diffusion ◽  
The Impact

Abstract Water vapour sorption experiments are frequently used to characterise the absorption and desorption of water in wood during transient conditions in relative humidity. When interpreting such experiments, it is still unclear to what extend the resulting time-dependent change of sample mass (i.e. sorption kinetics) is influenced by moisture transport, sorption and sorption related processes. To evaluate the impact of water vapour diffusion under such transient conditions, this study investigates the sorption kinetics of small wood samples with different lengths of transport pathways in and across fibre direction. For this purpose, water vapour sorption experiments on Norway spruce ( Picea abies ) samples were performed under identical climatic conditions at ambient air pressure and ambient standard temperature. The results showed that sample thickness has an impact on the sorption kinetics along the whole tested range of relative humidity. Differences between the sorption kinetics for samples in and across fibre direction were considerable at low relative humidity, indicating the relevance of water vapour diffusion through the lumen-pit-ray system. In contrast at high relative humidity, differences between the sorption kinetics for samples in and across fibre direction started to disappear while the impact of sample thickness was still considerable. Therefore, it seems as if an additional or modified process that depends on the number of sorption sites becomes relevant at an increased moisture content of wood. This process, as well as the increasing uptake and release of water across fibre direction, should be further investigated to gain a better understanding of the absorption and desorption of water in wood.

Analysis of the water vapour sorption behaviour of Sitka spruce [Picea sitchensis (Bongard) Carr.] based on the parallel exponential kinetics model

Holzforschung ◽  
2010 ◽  
Vol 64 (4) ◽  
Author(s):  
Callum A.S. Hill ◽  
Andrew Norton ◽  
Gary Newman
Keyword(s):  
Water Vapour ◽  
Sitka Spruce ◽  
Sorption Kinetics ◽  
Picea Sitchensis ◽  
Sorption Kinetic ◽  
Sorption Behaviour ◽  
Water Vapour Sorption ◽  
Vapour Sorption ◽  
Different Temperatures

Abstract The water vapour sorption behaviour of Sitka spruce was analysed based on the parallel exponential kinetics (PEK) model. The PEK model deconvolutes the sorption kinetics curve into two exponential kinetics processes (fast and slow) which have characteristic times and moisture contents associated with them. The sorption kinetics was examined at different temperatures enabling the determination of activation energies for the sorption kinetic processes throughout the hygroscopic range (from 5% to 95% relative humidities). The physical interpretation of the PEK model is also discussed.

Investigating water vapour sorption kinetics of aluminium MOFs by powder X-ray diffraction

CrystEngComm ◽  
2019 ◽  
Vol 21 (15) ◽  
pp. 2551-2558 ◽  
Author(s):  
Dominik Fröhlich ◽  
Philipp Hügenell ◽  
Helge Reinsch
Keyword(s):  
Water Vapour ◽  
Water Sorption ◽  
Sorption Kinetics ◽  
X Ray Diffraction ◽  
Sorption Behaviour ◽  
Water Vapour Sorption ◽  
X Ray ◽  
Vapour Sorption ◽  
Kinetics Of

The water sorption behaviour of aluminium MOF CAU-10 and CAU-15-Cit was followed by in situ powder X-ray diffraction.

scholarly journals Sorption and wetting properties of pectin edible films

2012 ◽  
Vol 30 (No. 5) ◽  
pp. 446-455 ◽  
Author(s):  
S. Galus ◽  
A. Turska ◽  
A. Lenart
Keyword(s):  
Water Vapour ◽  
Sorption Isotherms ◽  
Sorption Kinetics ◽  
Edible Films ◽  
Glycerol Concentration ◽  
Water Vapour Sorption ◽  
Vapour Sorption ◽  
Vapour Adsorption ◽  
Water Vapour Adsorption ◽  
Kinetics And Isotherms

The water vapour sorption kinetics and isotherms of pectin films prepared by the casting method were determined. The measurement of water vapour sorption kinetics was conducted using a saturated sodium chloride solution to obtain constant relative humidity of the environment (75.3%). The measurement was carried out at the temperature of 25°C over a 24 h period. The water vapour adsorption rate was the highest in the first hours of the process. The exponential equation fitted well the experimental data of water vapour adsorption with time. Glycerol concentration in the analysed films affected the increasing water vapour adsorption. The water vapour sorption isotherms were analysed using the saturated salt solutions with water activity from 0.113 to 0.901 for 3 months at 25°C. The sorption isotherms curves had a sigmoidal shape for all films. Glycerol content affected water vapour adsorption during 3 months. Peleg’s equation was appropriate for the mathematical description of the sorption isotherms. The microstructure of pectin films showed different internal arrangement as a function of the film composition.  

Water vapour sorption of wood modified by acetylation and formalisation – analysed by a sorption kinetics model and thermodynamic considerations

Holzforschung ◽  
2016 ◽  
Vol 70 (3) ◽  
pp. 203-213 ◽  
Author(s):  
Sarah Himmel ◽  
Carsten Mai
Keyword(s):  
Cell Wall ◽  
Water Vapour ◽  
Sorption Process ◽  
Sorption Kinetics ◽  
Constant Factor ◽  
Sorption Data ◽  
Sorption Behaviour ◽  
Water Vapour Sorption ◽  
Vapour Sorption ◽  
Surface Work

Abstract The water vapour sorption data of untreated (Wuntr), acetylated (Wac) and formaldehyde-treated (WFA) Scots pine (Pinus sylvestris L.) sapwood were analysed in terms of their sorption kinetics and were transformed into excess surface work (ESW) isotherms. The sorption kinetics were studied by fitting the non-linear parallel exponential kinetics (PEK) model to the experimental data in which the sorption kinetics curve is composed of two processes (fast and slow components). Wac and WFA showed evident differences in their sorption kinetics and their thermodynamic sorption behaviour. In contrast to acetylation, formalisation influenced both the extent of the slow sorption process and the shape of its pseudoisotherm. For Wuntr and Wac, it appears that some water associated with the slow process is adsorbed at sites for fast sorption newly generated upon swelling (previously postulated as extra water) and subsequently desorbed by the fast process. For WFA, the formation of extra water hardly occurs. ESW was reduced through acetylation with a constant factor over the whole hydroscopic range, whereas the ESW of WFA was reduced only after reaching the monolayer capacity compared to its control. The sorption behaviour of Wac was solely determined by cell wall bulking, whereas that of WFA was governed by the increased matrix stiffness due to cross-linking of the cell wall polymers.

scholarly journals On the mechanism of water vapour sorption from unsaturated atmospheres by ticks

1997 ◽  
Vol 200 (10) ◽  
pp. 1491-1498 ◽  
Author(s):  
K Gaede ◽  
W Knülle
Keyword(s):  
Relative Humidity ◽  
Water Vapour ◽  
Adsorbed Water ◽  
Salivary Secretion ◽  
Sorption Kinetics ◽  
Measurement Range ◽  
Water Vapour Sorption ◽  
Critical Equilibrium ◽  
Kinetics Of ◽  
Water Vapour Uptake

The nascent salivary secretion of 41 partly dehydrated and unfed adult female Amblyomma variegatum, 5­8 months post-ecdysis, during water vapour uptake at 93.5 % relative humidity and 20 °C, had an osmolality of between 298.6 and 769.7 mosmol kg-1 (mean ± s.d. 470.3±85.8 mosmol kg-1). This range would allow water vapour uptake at relative humidities of approximately 98­99 %, but it would not suffice for lower relative humidities down to 80­85 %, the critical equilibrium humidity of A. variegatum. At this relative humidity (85 %), an osmolality of 9796 mosmol kg-1 is required for water vapour uptake. It is proposed that hydrophilic cuticle in the hypostome could play a role in water condensation and that the slightly hyperosmotic secretion of the agranular alveoli of the salivary glands might alter the water affinity at the adsorbing cuticle surface and release the adsorbed water. The water-enriched secretion would then be drawn into the mouth by the powerful suction of the pharynx. This hypothetical hydrophilic cuticle component of water vapour uptake in A. variegatum merits closer investigation. The sorption kinetics of A. variegatum support an additional 'osmotic' component of water vapour uptake at humidities near saturation. A nanolitre osmometer particularly suited to sample volumes smaller than 5 nl was developed. This device does not require the transfer of fluid after collection, and its measurement range is extended beyond the 5 osmol kg-1 that can be measured using commercial apparatus.

Untersuchungen zum Diffusionswiderstand von Holzwerkstoffen | Diffusion resistance of timber materials

2005 ◽  
Vol 156 (3-4) ◽  
pp. 100-103
Author(s):  
Rudolf Popper ◽  
Peter Niemz ◽  
Gerhild Eberle
Keyword(s):  
Relative Humidity ◽  
Water Vapour ◽  
Middle Lamella ◽  
Solid Wood ◽  
Diffusion Resistance ◽  
Water Vapour Diffusion ◽  
Wood Panels ◽  
Vapour Diffusion ◽  
Wet Climate ◽  
Panel Thickness

The water vapour diffusion resistance of timber materials were tested in a wet climate (relative humidity ranging from 100%to 65% at 20 °C) and in a dry climate (relative humidity ranging from 0% to 65% and from 0% to 35% at 20 °c) with variation by relative humidity and vapour pressure gradient. The diffusion resistance of multilayer solid wood panels lies under or within the range of the solid wood (spruce), tending even to a lower range. This can be attributed to the loosely inserted middle lamella of the used solid wood panels, which were not correctly glued by the manufacturer. The diffusion resistance of the solid wood panels increases with decreasing moisture content and decreasing panel thickness, as well as with increasing water vapour gradient from 818 to 1520 Pa. There were clear differences between the tested timber materials. The diffusion resistance of particle composites is strongly dependent on the specific gravity. Due to laminar particles OSBs(Oriented Strand Boards) have a larger diffusion resistance than chipboards. The water vapour diffusion resistance of OSBs lies within the range of plywood.

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