On the importance of heat and mass transfer coupling during characterization of hygroscopic insulation materials

Abstract

The present work is focused on mass transfer characterization of hygroscopic materials used for insulation, such as Low Density Fibreboards. Due to their particular morphology, these panels present a very high mass diffusivity in the connected gaseous phase and a very low thermal conductivity. This combination of properties exacerbates the coupling between heat and mass transfer in transient state. Based on experimental data obtained with an original set-up and relevant simulations performed using a comprehensive physical formulation, a throughout vision of this question is proposed in the present study. In particular, we emphasize on: - The impressive change in core temperature in terms of magnitude and duration, - The great impact of the internal temperature gradient, which slows down mass diffusion, - The dramatic error on mass diffusivity value if the coupling is ignored. Keywords: experiment; identification; modelling; RH at back-face; transient state