Measurement of the thermal diffusivity of molten salts by the forced Rayleigh scattering method

Measurements were made of the thermal diffusivity of five molten alkali metal chlorides (LiCl, NaCl, KCl, RbCl, and CsCl) in the temperature range above 1000 °C by the forced Rayleigh scattering method. K₂Cr₂O₇ was used as the dye substance in order to colour the transparent molten salts. The accuracy was estimated to be ±4% to ±11%, depending on the measured salts. In comparison with the present results converted into thermal conductivity, most of the previous experimental data obtained by the steady-state methods show values up to about five times larger, which may be due to the presence of convection and radiation. It was found that the thermal conductivity of this series of molten alkali metal chlorides decreases with increasing molecular weight, and that this temperature coefficients are weakly negative.