Inclusion of the sorption hysteresis phenomenon in future drying models: Some basic considerations

The sorption hysteresis effect, i.e. different wood equilibrium moisture contents (EMCs) in desorption and adsorption for the same relative humidity, is well known. However, quantitative sorption isotherms, in the form of tables or analytical correlations, are almost always given as the average of t...

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Autor principal:	Salin,Jarl-Gunnar
Lenguaje:	English
Publicado:	Universidad del Bío-Bío 2011
Materias:	Modelling sorption hysteresis wood drying
Acceso en línea:	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2011000200005
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spelling	oai:scielo:S0718-221X20110002000052011-08-24Inclusion of the sorption hysteresis phenomenon in future drying models: Some basic considerationsSalin,Jarl-Gunnar Modelling sorption hysteresis wood drying The sorption hysteresis effect, i.e. different wood equilibrium moisture contents (EMCs) in desorption and adsorption for the same relative humidity, is well known. However, quantitative sorption isotherms, in the form of tables or analytical correlations, are almost always given as the average of the desorption and adsorption curves. Consequently most drying simulation models use these average curves, and does not take into account the sorption hysteresis phenomenon. The equilibrium state of a wood sample is thus not a function of the relative humidity only, but depends on the moisture history also. This means that Fick's equations - with moisture content as a single driving force - are not valid any more. For a pure desorption process the state of the sample follows the desorption isotherm, but a problem arises when desorption is followed by adsorption - as for instance in the timber conditioning phase. It seems reasonable to assume that for each EMC point, on or between the desorption/adsorption isotherms, the moisture content change follows a unique path when the surrounding climate changes. This path - the so called scanning curve - does not need to be the same in desorption and adsorption. Some selected results and corresponding scanning curve suggestions are presented and discussed. Drying models with the sorption hysteresis phenomenon included should be developed for the analysis of experimental data and more generally for use as an improved tool in practical applications.info:eu-repo/semantics/openAccessUniversidad del Bío-BíoMaderas. Ciencia y tecnología v.13 n.2 20112011-01-01text/htmlhttp://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2011000200005en10.4067/S0718-221X2011000200005
institution	Scielo Chile
collection	Scielo Chile
language	English
topic	Modelling sorption hysteresis wood drying
spellingShingle	Modelling sorption hysteresis wood drying Salin,Jarl-Gunnar Inclusion of the sorption hysteresis phenomenon in future drying models: Some basic considerations
description	The sorption hysteresis effect, i.e. different wood equilibrium moisture contents (EMCs) in desorption and adsorption for the same relative humidity, is well known. However, quantitative sorption isotherms, in the form of tables or analytical correlations, are almost always given as the average of the desorption and adsorption curves. Consequently most drying simulation models use these average curves, and does not take into account the sorption hysteresis phenomenon. The equilibrium state of a wood sample is thus not a function of the relative humidity only, but depends on the moisture history also. This means that Fick's equations - with moisture content as a single driving force - are not valid any more. For a pure desorption process the state of the sample follows the desorption isotherm, but a problem arises when desorption is followed by adsorption - as for instance in the timber conditioning phase. It seems reasonable to assume that for each EMC point, on or between the desorption/adsorption isotherms, the moisture content change follows a unique path when the surrounding climate changes. This path - the so called scanning curve - does not need to be the same in desorption and adsorption. Some selected results and corresponding scanning curve suggestions are presented and discussed. Drying models with the sorption hysteresis phenomenon included should be developed for the analysis of experimental data and more generally for use as an improved tool in practical applications.
author	Salin,Jarl-Gunnar
author_facet	Salin,Jarl-Gunnar
author_sort	Salin,Jarl-Gunnar
title	Inclusion of the sorption hysteresis phenomenon in future drying models: Some basic considerations
title_short	Inclusion of the sorption hysteresis phenomenon in future drying models: Some basic considerations
title_full	Inclusion of the sorption hysteresis phenomenon in future drying models: Some basic considerations
title_fullStr	Inclusion of the sorption hysteresis phenomenon in future drying models: Some basic considerations
title_full_unstemmed	Inclusion of the sorption hysteresis phenomenon in future drying models: Some basic considerations
title_sort	inclusion of the sorption hysteresis phenomenon in future drying models: some basic considerations
publisher	Universidad del Bío-Bío
publishDate	2011
url	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2011000200005
work_keys_str_mv	AT salinjarlgunnar inclusionofthesorptionhysteresisphenomenoninfuturedryingmodelssomebasicconsiderations
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Inclusion of the sorption hysteresis phenomenon in future drying models: Some basic considerations

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