On Monday, October 8, 2018, Thomas BUSSER, a PhD student in Civil Engineering and Habitat Sciences at the Laboratory for Design Optimization and Environmental Engineering (LOCIE), will be defending his thesis "Study of hygrothermal transfers in wood-based materials and their contributions to the interior ambience of buildings".
The defense will take place at 1:30 pm, in amphitheater C002 of the Bâtiment Polytech (B2), on the Bourget-du-Lac campus.
Summary of the thesis
Some studies report that the behavior of wood constructions is not correctly predicted by conventional engineering models. These discrepancies could be explained by the impact of moisture, latent heat and the hygrothermal behavior of wood-based materials under transient conditions, although this remains an open question. This is the background to this work: the overall aim is to improve understanding and modelling of coupled heat and mass transfers in wood-based materials, and consideration of their effects on the indoor environment. To achieve these objectives, we are tackling different scales: material, wall and air volume. The main challenges are - characterizing the properties of highly hygroscopic materials and understanding coupled transfers, - quantifying the impact of transfers on indoor climate and performance. This thesis work focused on the following 3 actions: - A dynamic characterization protocol was defined and applied to wood fiber and solid wood samples. Particular attention was paid to validating the protocol and taking experimental uncertainties into account. The measurements carried out enabled the hygric properties to be identified in a diffusive model using an algorithm based on an inverse method. - Modeling coupled heat, air and moisture transfer in hygroscopic materials The assumptions of the purely diffusive model were discussed, taking into account air advection and local non-equilibrium between water vapor and bound water. A comparison between the models and experimental results shows that their impact is relatively low. The local sensitivity analysis also confirms these results. Estimation of the non-equilibrium model parameters nevertheless improves prediction compared with the diffusive model alone. - Evaluation at air volume scale In order to study transfers in a volume of air, an experimental set-up was constructed using wood panels. The experimental results enable us to validate the numerical model at this scale, using the properties determined at the material scale, and to study transfer phenomena and their impact on the indoor environment. The model shows that taking into account coupled transfers has little impact on average heating consumption, but that power demand is lower when humidity levels vary.