Design and test of an apparatus for transient measurements of the thermal conductivity and volumetric heat capacity of solids

Authors: FLORIAN GATHER, EKREM GÜNEŞ, PETER J. KLAR

Abstract: Knowledge of the thermal conductivity (κ) of solids is crucial for all thermoelectric devices. A new approach in transient measurement to determine this value as well as electric conductivity (σ) and the Seebeck coefficient (S) is presented here. This approach can be combined with current steady-state methods. A cylindrical sample is mounted between two heat-flux sensors that can be heated or cooled at their outer ends. The input signals defining the heat fluxes at the sensors can be any arbitrary function of time, although some waveforms yield more valid results. The method is evaluated by employing a one-dimensional numerical model and finding the best fit to extract the thermal conductivity (κ) of the sample as well as its volumetric heat capacity (cρ) . Trial measurements on an insulating (σ = 1 × 1013 Sm^-1) and a conducting sample (σ = 1 × 105 Sm^-1) are presented and the results are in good agreement with the literature and data obtained by a commercial laser-flash analysis system. Improvements in comparison to present measurement methods are the direct determination of κ compared to other transient methods like laser-flash analysis, shorter measurement times by acquiring κ(T) data in a single temperature approach, and simultaneous S and σ measurements.

Keywords: Thermal transport, steady-state measurement, dynamic measurement, ZT-meter

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