A new thermal conductivity probe for high temperature tests for the characterization of molten salts

A new thermal conductivity probe for high temperature (HT-TCP) has been built and tested. Its design and construction procedure are adapted from the ambient temperature thermal conductivity probe (AT-TCP) due to good performance of the latter device. The construction procedure and the preliminary tests are accurately described. The probe contains a Pt wire as a heater and a type K thermocouple (TC) as a temperature sensor, and its size is so small (0.6 mm in diameter and 60 mm in length) as to guarantee a length to diameter ratio of about 100. Calibration tests with glycerol for temperatures between 0 °C and 60 °C have shown good agreement with literature data, within 3%. Preliminary tests were also carried on a ternary molten salt for Concentrated Solar Power (CSP) (18% in mass of NaNO₃, 52% KNO₃, and 30% LiNO₃) at 120 °C and 150 °C. Obtained results are within λ range of the Hitec^® salt (53% KNO₃, 7% NaNO₃, 40% NaNO₂). Unfortunately, at the higher temperature tested (200 °C), the viscosity of the salt highly decreases, and free convection starts, making the measurements unreliable.