Parametric identification of thermophysical properties in masonry walls of buildings
Résumé
The objective of this work is to improve the knowledge on the thermophysical characterization of opaque walls by determining the thermophysical properties of an experimental massive brick wall identical to old buildings walls in the North of Europe. This method allows the determination of equivalent dynamic thermal properties of existing building walls λ and ρCp by simple measurement records of the inner (Twi) and outer (Two) wall temperatures as well as heat flux at the inner (or outer) face of the wall Fi. The approach developed here consists in carrying out a parametric identification of the thermophysical properties of the wall in question (namely the thermal conductivity λ and the heat capacity ρCp), by comparing and minimizing the difference between the results resulting from the experimental tests and those resulting from the numerical model. The optimization of the identified parameters is based on the Levenberg-Marquardt algorithm via the Comsol tool. The validation of the algorithm was carried out as well as its use in different ambient conditions (harmonic and random temperature profiles). The investigated method shows satisfactory results for both λ (0.877, 0.880, and 0.935 W/(m.K)) and ρCp (1,012,400, 944,710, and 1,057,100 J/(m3.K)). The inner heat exchange coefficient hi was also successfully determined for the three tests with similar values (6.13, 6.53, and 6.03 W/m2.K). The results were also confirmed by comparing measured and numerical outer heat fluxes for the optimized values. The second part of this article is devoted to the study of the sensitivity of the results with respect to various parameters: the optimization algorithm, the total simulation time, the simulation time step, and the meshing element size.
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