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Inter-laboratory comparison on thermal conductivity measurements by the guarded hot plate method between LNE and institute VINČA
Bruno Hay, Nenad Milošević, Jacques Hameury, Nenad Stepanić, Guillaume Failleau, Yann Garcia, Alain Koenen and Jen-Rémy Filtz

An inter-laboratory comparison has been organized between LNE and Institute VINČA, respectively French National Metrology Institute and Serbian Designated Institute for thermal properties metrology, on thermal conductivity measurements by the guarded hot plate method. The main objective was to validate the measurement capabilities of VINČA in terms of thermal conductivity in the temperature range from 10 °C to 50 °C by using the facility improved in the frame of the European project Eura-Thermal.

The measurements were carried out on expanded polystyrene boards using guarded hot plate apparatuses (two-specimen GHP apparatuses) in accordance with the international standard ISO 8302. The measurement programme was defined taking into account the major characteristics of the guarded hot plate apparatuses used, such as specimen dimensions and temperature and thermal conductivity ranges. Specimens were machined by LNE from a same batch for both participants. Prior to the measurements, the homogeneity of the set of specimens as well as the influence of a variation of density of the expanded polystyrene on the thermal conductivity measurements were studied by VINČA.

The obtained results showed good agreement between the two laboratories, with relative deviations within the uncertainties of measurement. Also, the results validated the level of uncertainty assessed by VINČA for its thermal conductivity measurements to around 2.5 % (with a coverage factor of 2) between 10 °C and 50 °C.

Keywords: Thermal conductivity, guarded hot plate, insulating materials, metrology

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