Evaluation of moisture sorption models and modified Mualem model for prediction of desorption isotherm for wood materials

Publication date: October 2015
Source:Building and Environment, Volume 92
Author(s): Xiaobo Zhang , Wolfgang Zillig , Hartwig M. Künzel , Xu Zhang , Christoph Mitterer
Modeling of heat and moisture transport in wood based materials requires the knowledge of material properties such as sorption isotherms. Several water vapor sorption models available in literature are evaluated by fitting the sorption isotherm data of spruce (Picea abies) at 23 °C. To take temperature effect into account, temperature dependent sorption models are adopted to fit the sorption data of Klinki pine at four temperatures. The results show that the Guggenheim-Anderson-de Boer (GAB) model, thermodynamic model and Dubinin-Astakhov (DA) function based on Polanyi moisture chemical potential have comparable excellent performances for fitting of sorption data. A modified Mualem model with a variable exponent, which is established based on similarity hypothesis, is used to generate desorption isotherm from measured adsorption isotherm. Only another intermediate point on desorption isotherm needs to be measured for the calibration of the exponent. If the sorption history of desorption isotherm is unknown, the measured desorption point will be preferred as the starting point for predicting desorption isotherm. Therefore, the experimental efforts to determine the main isotherm branches can be greatly reduced.