The successful measurement of the thermal conductivity of molten salts is
a challenging undertaking due to the electrically conducting and possibly also
aggressive nature of the materials, as well as the elevated temperatures at
which these data are required. For accurate and reproducible measurements
it is important to develop a suitable experimental apparatus and methodology.
In this study we explore a modified version of the transient hot-wire
method, which employs a molten-metal-filled capillary in order to circumvent
some of the issues encountered in previous studies. Specifically, by using a
novel flexible U-shaped quartz-capillary, filled with a eutectic mixture of gallium,
indium and tin, commercially known as Galinstan, we proceed to measure
the thermal conductivity of molten eutectic KNO3−NaNO3−NaNO2.
The new probe is demonstrated as being able to measure the thermal conductivity
of this molten salt, which is found to range from 0.48 W/m K at
500 K to 0.47 W/m K at close to 700 K, with an overall expanded uncertainty
(95% confidence) of 3.1%. The quartz is found to retain its electrically
insulating properties and no current leakage is detected in the sample over
the investigated temperature range. The thermal conductivity data reported
in the present study are also used to elucidate a partial disagreement found
in the literature for this material.