Influence of mass transfer on the estimation of the thermal conductivity of a wet material by the hot wire and parallel hot wire methods

Biosourced insulating materials can provide an interesting response to climate challenges by reducing the energy consumption of buildings without using petroleum-based products. Compared to traditional insulating materials, they have the particularity of being hydrophilic so that mass transfer by water evap-oration and condensation occurs when temperature or humidity boundary conditions change. To estimate the influence of mass transfer on the thermal conductivity estimation in the hot wire and in the paral -lel hot wire method, a coupled heat/mass transfer 1D model in cylindrical geometry was developed and numerically solved. Its exploitation to perform numerical experiments showed that the hot wire method allows the measurement of the thermal conductivity while the parallel hot wire method allows the mea-surement of an equivalent conductivity, sum of the thermal conductivity and of a term related to the phase change phenomena of water within the medium. These theoretical results were confirmed by an experimental study carried out on an anisotropic wood wool.(c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

Biosourced insulating materials present an interesting alternative to petroleum-based products for reducing building energy consumption in response to climate challenges. These materials have the unique feature of being hydrophilic, enabling mass transfer through water evaporation and condensation. A heat/mass transfer 1D model in cylindrical geometry was developed and solved numerically to assess the influence of mass transfer on thermal conductivity estimation using the hot wire and parallel hot wire methods. Experimental results on an anisotropic wood wool confirmed the theoretical findings that the hot wire method measures thermal conductivity while the parallel hot wire method measures an equivalent conductivity that includes the phase change phenomena of water in the medium. Importance rating for this article: 8 out of 10.