On Monday, October 8, 2018, Thomas BUSSER, a doctoral student in Civil Engineering and Housing Sciences at the Laboratory for Design Optimization and Environmental Engineering (LOCIE), will defend his dissertation titled “Study of hygrothermal transfers in wood-based materials and their impact on indoor environmental quality in buildings.”
The defense will take place at 1:30 p.m. in Lecture Hall C002 of the Polytech Building (B2) on the Bourget-du-Lac campus.
Thesis summary
Some studies report that the behavior of wood structures is not accurately 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 work fits into this context: the overall objective is to improve the understanding and modeling of coupled heat and mass transfers in wood-based materials and to account for their effects on the indoor environment. To achieve these objectives, we address different scales: material, wall, and air volume. The main challenges to be addressed are: – The accurate characterization of the properties of highly hygroscopic materials and the understanding of coupled transfers, – The quantification of the impact of these transfers on indoor climate and performance. This thesis work focused on the following three areas: – Methodology for the hygroscopic characterization of materials A dynamic characterization protocol was defined and then applied to samples of wood fiber and solid wood. Particular attention was paid to validating the protocol and accounting for experimental uncertainties. The measurements performed enabled the identification of hygroscopic properties within a diffusive model using an algorithm based on an inverse method. – Modeling of coupled heat, air, and moisture transfers in hygroscopic materials The assumptions of the purely diffusive model were discussed, taking into account air advection and the local non-equilibrium between water vapor and bound water. The comparison between the models and the experimental results shows that their impact is relatively small. The local sensitivity analysis performed also confirms these results. Estimating the parameters of the non-equilibrium model nevertheless improves the prediction compared to the diffusive model alone. – Evaluation at the air volume scale To study transfers within an air volume, an experimental setup was constructed using wooden panels. The experimental results validate the numerical model at this scale using properties determined at the material scale and allow for the study of transport phenomena and their impact on the indoor environment. The model demonstrates that accounting for coupled transport processes has little effect on average heating consumption but that, during humidity variations, the required heating power is lower.