Abstract
Sorption of water vapour in hygroscopic porous materials is associated with latent heat release and absorption. This phenomenon should be taken into account to achieve a better understanding of the coupled transfer of vapour and heat in hygroscopic porous materials. In this paper, water vapour adsorption and desorption in the longitudinal direction of spruce samples are studied. Neutron radiography is used to measure changes in moisture content and wireless thermocouples are used to measure temperature changes. During the adsorption and desorption experiments, large changes in moisture content and temperature are observed. A hygrothermal model is developed to simulate vapour and heat transfer during adsorption and desorption experiments. Generally, the numerical model predicts well the measured moisture and temperature changes. The large moisture change is due to the low vapour resistance factor in the longitudinal direction of the spruce samples. The latent heat associated with vapour adsorption is the cause of the large temperature changes. It was found that vapour permeability affects both vapour and heat transfer, while thermal conductivity only affects heat transfer.
Highlights
The capability of hygroscopic materials to moderate indoor humidity changes has been extensively studied [1,2]
Samples are equilibrated as follows: the sample for the adsorption experiment is stored in a desiccating cabinet with silica gel particles and the sample for the desorption experiment is stored in a cabinet over NH4H2PO4 solution
Result The simulated and measured temperature and moisture content changes in the adsorption experiment and desorption experiments are compared in Figures 11 and 12
Summary
The capability of hygroscopic materials to moderate indoor humidity changes has been extensively studied [1,2]. This work uses state-ofthe-art experiments and numerical models to study moisture and temperature transport in wood during adsorption and desorption. Both temporal and spatial changes of moisture content and temperature are documented and analyzed.
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