Experimental campaign on thermal conductivity measurements with heat flow meter apparatus: Compliance with current standards

This work is aimed at verifying the compliance of a steady-state experimental apparatus for measuring thermal conductivity according to the current standard's requirements. The most significant checks were performed on the following parameters: flatness, emissivity and temperature distribution on the heating and cooling plates, number and location of temperature sensors and emissivity of the two heat flow meters. As specified by the standards, contrary to the guarded hot plated method, the heat flow meter method is an indirect technique, because measurements are based on the knowledge of the conductivity of a reference element. A glass wool specimen, used as the Italian standard for conductivity measurements, has been employed for checking the heat flux meters against possible drift errors in their calibration curve. A set of tests, in which the previous calibration factor was employed, have shown that all the measurements performed led to values of the calculated thermal conductivity which are contained within the experimental uncertainty. Subsequently, a specimen made of polystyrene has been tested in three different period of the year with different external temperature conditions. The performed tests allowed validation of the apparatus, which was proved to yield repeatable and reliable measurements.