InterPore2026

Development and experimental validation of a physically-based hygrothermal model for bio-based materials

19 May 2026, 12:05

15m

Oral Presentation (MS16) Complex fluid and Fluid-Solid-Thermal coupled process in porous media: Modeling and Experiment MS16

Speaker

Nicolas Daunais (Université Gustave Eiffel)

Description

In the context of climate emergency, bio-based building materials offer strong potential to reduce the carbon footprint of the construction industry while regulating temperature and humidity fluctuations. Their hygrothermal behavior results from coupled fluid–solid–thermal processes: moisture is transported in the pore space as a mixture of dry air and water vapor, and within the solid matrix as bound water, both driving energy transport by advection. Sorption and desorption phenomena occurring between phases further couple mass transfer to heat through latent effects. Accurately capturing these mechanisms is essential for predictive modeling, experimental characterization of properties and, consequently, for the integration of these materials into the building sector. However, despite extensive research, the literature reports persistent discrepancies between simulations and experiments, especially for the spatio-temporal evolution of moisture fields [1]. At the same time, most classical models remain largely phenomenological and rely on effective transport coefficients with limited physical meaning [2,3]. In particular, bound water transport is often poorly understood and therefore entirely neglected without clear justification in current models.

In the present work, we address this gap with a physically based macroscopic hygrothermal model that explicitly distinguishes vapor transport in the pores from bound water diffusion in the solid matrix [4]. The formulation leads to two coupled partial differential equations driven by relative humidity~$\phi$ and temperature~$T$, with constitutive parameters that are independently measurable rather than calibrated. A scaling analysis identifies key dimensionless numbers that delineate coupling regimes and indicates that, under comparable gradients, heat transfer is typically faster than moisture migration and that temperature variations exert a stronger influence on moisture evolution than the reverse.

Finally, we perform a material-scale experimental validation on a cellulose-based sample of the previously established hygrothermal model. A dedicated drying experiment is designed to measure temperature and moisture fields simultaneously under tightly controlled boundary conditions. The experiment is supported by an independent characterization of the material's thermophysical and hygroscopic properties. The model shows very good agreement with measurements in both timing and magnitude, particularly for spatially averaged temperature and humidity, while remaining discrepancies in local profiles are discussed in terms of experimental uncertainties (e.g., sensor positioning and local measurement disturbance).