An apparatus for precise and absolute measurement of the thermal conductivity of electrically conducting liquids using the transient hot-wire method has been developed. In the present apparatus, a metallic wire coated with a thin electrical insulation layer has been used as a heating element and a resistance thermometer instead of a bare metallic wire. The effects on the thermal conductivity measurement caused by the thin insulation layer have been analysed. In the analysis, it was found that the effects can be negligibly small if the instrument is adequately designed. The usability of the method for electrically conducting liquids has been tested to measure the thermal conductivity of an aqueous NaCl solution in the temperature range 0 to 45 degrees C at atmospheric pressure. The accuracy of the present measurement was estimated to be +or-0.5%.
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