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Modelling over-hygroscopic wood sorption isotherms based on quantitative wood anatomy

Fredriksson, Maria LU ; Engelund Thybring, Emil and Garbrecht Thygesen, Lisbeth (2017) 13th annual meeting of the Northern European Network for Wood Science and Engineering (WSE2017) p.142-147
Abstract
A sorption isotherm expresses the relation between ambient relative humidity (RH) and equilibrium moisture content of a material for a specific temperature. The sorption isotherm can generally be divided into a hygroscopic part covering low, medium and high RH levels, and an over-hygroscopic part close to 100% RH. For wood, the hygroscopic part is dominated by water uptake in cell walls and the over-hygroscopic part by capillary condensed water in cell lumina and other voids within the wood structure. Moisture contents in the over-hygroscopic range are required for fungal degradation, and over-hygroscopic sorption isotherms are thus relevant input data for models describing moisture conditions in outdoor structures, i.e. models needed for... (More)
A sorption isotherm expresses the relation between ambient relative humidity (RH) and equilibrium moisture content of a material for a specific temperature. The sorption isotherm can generally be divided into a hygroscopic part covering low, medium and high RH levels, and an over-hygroscopic part close to 100% RH. For wood, the hygroscopic part is dominated by water uptake in cell walls and the over-hygroscopic part by capillary condensed water in cell lumina and other voids within the wood structure. Moisture contents in the over-hygroscopic range are required for fungal degradation, and over-hygroscopic sorption isotherms are thus relevant input data for models describing moisture conditions in outdoor structures, i.e. models needed for service life prediction. The over-hygroscopic range is also relevant when modelling wood drying. Measuring over-hygroscopic absorption and desorption isotherms is however time consuming and challenging and a model enabling prediction of over-hygroscopic sorption isotherms would therefore be valuable. In addition, such a model could give a better understanding of how the wood structure affects the capillary condensation of water. This paper presents an approach for modelling over-hygroscopic sorption isotherms based on quantitative wood anatomy, i.e. based on estimates of dimensions and geometries of voids in the wood structure available for capillary condensation. First results are shown for Norway spruce (Picea abies (L.) Karst.). (Less)
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author
organization
publishing date
type
Contribution to conference
publication status
published
subject
keywords
sorption isotherm, over-hygroscopic moisture range, model, wood anatomy
pages
6 pages
conference name
13th annual meeting of the Northern European Network for Wood Science and Engineering (WSE2017)
language
English
LU publication?
yes
id
1d579a5f-1914-49e9-91cc-8e8544da609a
date added to LUP
2017-10-03 10:03:17
date last changed
2017-11-28 08:44:48
@misc{1d579a5f-1914-49e9-91cc-8e8544da609a,
  abstract     = {A sorption isotherm expresses the relation between ambient relative humidity (RH) and equilibrium moisture content of a material for a specific temperature. The sorption isotherm can generally be divided into a hygroscopic part covering low, medium and high RH levels, and an over-hygroscopic part close to 100% RH. For wood, the hygroscopic part is dominated by water uptake in cell walls and the over-hygroscopic part by capillary condensed water in cell lumina and other voids within the wood structure. Moisture contents in the over-hygroscopic range are required for fungal degradation, and over-hygroscopic sorption isotherms are thus relevant input data for models describing moisture conditions in outdoor structures, i.e. models needed for service life prediction. The over-hygroscopic range is also relevant when modelling wood drying. Measuring over-hygroscopic absorption and desorption isotherms is however time consuming and challenging and a model enabling prediction of over-hygroscopic sorption isotherms would therefore be valuable. In addition, such a model could give a better understanding of how the wood structure affects the capillary condensation of water. This paper presents an approach for modelling over-hygroscopic sorption isotherms based on quantitative wood anatomy, i.e. based on estimates of dimensions and geometries of voids in the wood structure available for capillary condensation. First results are shown for Norway spruce (Picea abies (L.) Karst.).},
  author       = {Fredriksson, Maria and Engelund Thybring, Emil and Garbrecht Thygesen, Lisbeth},
  keyword      = {sorption isotherm,over-hygroscopic moisture range,model,wood anatomy},
  language     = {eng},
  pages        = {142--147},
  title        = {Modelling over-hygroscopic wood sorption isotherms based on quantitative wood anatomy},
  year         = {2017},
}