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Short time non-destructive evaluation of thermal performances of building walls by studying transient heat transfer

•Thermal quadrupoles formalism is applied for modelling transient heat transfers in building walls with a semi-infinite assumption.•Front face response curves of multi-layered walls are analysed to estimate the thermal properties of the wall.•Experiments are carried out on two classical multi-layere...

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Bibliographic Details
Published in:Energy and buildings 2019-02, Vol.184, p.141-151
Main Authors: Yang, Yingying, Wu, Tingting Vogt, Sempey, Alain, Dumoulin, Jean, Batsale, Jean-Christophe
Format: Article
Language:English
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Summary:•Thermal quadrupoles formalism is applied for modelling transient heat transfers in building walls with a semi-infinite assumption.•Front face response curves of multi-layered walls are analysed to estimate the thermal properties of the wall.•Experiments are carried out on two classical multi-layered building walls using artificial thermal excitations.•The proposed method reduces the evaluation time less than 10 hours. Thermal performances of building walls are significant for energy conservation. However, very few non-destructive evaluation methods exist to quantitatively diagnose the building walls in situ due to the walls’ large thickness. Moreover, most of the existing methods are inconvenient to implement in situ and take a long characterization time. This paper studies transient heat transfer to estimate the wall's thermal properties based on the thermal quadrupoles modelling. Semi-infinite boundary condition is assumed at the rear face of the wall. With this assumption, only the front face response of the wall is considered. The evaluation time is then effectively reduced within a few hours, and the diagnosis in situ is simplified without the measurement on the rear face of the wall. Experiments are carried out on two traditional multi-layered building wall cases using heating lamps. With the measured surface temperatures and heat fluxes, the unit-pulse response and unit-step response at the front surface of the investigated wall are reconstructed through a deconvolution approach and a TSVD (Truncated Singular Value Decomposition) inversion. The unit-step response curve is directly characterized by the thermal resistance, thermal effusivity and heat capacity of the wall, thus allowing us to estimate the wall properties. The characterization time for the two cases is less than 10 hours.
ISSN:0378-7788
1872-6178
DOI:10.1016/j.enbuild.2018.12.002