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Features of measuring the thermal diffusivity of molten salts in nickel cells using the laser flash method
Abstract
Reliable experimental data on the thermophysical properties of molten salts are essential for the design and optimization of various power plants. Measurement accuracy depends not only on the chosen method, the structural material, and the parameters of the measuring cells, but also on the quality of contact between the melt and the cell surface. This study investigated the influence of the surface roughness and topography of nickel cells on the thermal diffusivity of a molten eutectic NaCl-KCl, measured using the laser flash method. Different cell surface roughness was obtained by mechanical treatment, electrochemical polishing in acid solution, and anodic oxidation in LiOH and KOH melts. The roughness, determined with a profilometer, varied from 0.18 to 1.47 μm with an asperity height from 1.59 to 13.2 μm. The roughness parameters obtained by scanning probe microscopy (AFM) in 2D (10 x 10 μm) and 3D (10 x 10 x 10 μm) formats had significantly lower values (on the order of nanoscale values) for the machined and polished Ni samples. The results of measuring the thermal diffusivity of deionized water in all cells, except for the polished one, are almost identical but differ from the reference data by an average of 9 %. The thermal diffusivity obtained in cells with a roughness of at least 1.0 ± 0.5 μm (profilometer) was in a good agreement with the literature data. In a polished cell with a roughness less than 0.18 μm (profilometer) and 14 nm (AFM), the obtained results exceeded the published values by ~ 50 %. However, it was found that the nano-roughness of the nickel cell surface, determined using a micro-area scan (AFM), does not significantly affect the measurements.
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DOI: https://doi.org/10.15826/elmattech.2026.5.080
Copyright (c) 2026 Olga Yu. Tkacheva, Alexey V. Rudenko, Alexander A. Redkin
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