A Device for Measuring Thermal Conductivity of Molten Salt Nitrates at Elevated Temperatures for Use in Solar Thermal Power Applications

Binary and Ternary mixtures of Molten Salt Nitrates are ideal candidates for future concentrating solar power (CSP) plant heat transfer fluids (HTFs) because of their high operating temperature limits resulting in greater Rankine efficiency. The inclusion of these HTFs into CSP plants is expected to revolutionize the industry by allowing for energy and cost savings that are attractive to potential plant developers and investors. It is vital for plant designers to have access to fully characterized thermo-physical properties of the intended HTFs, with thermal conductivity, viscosity, and specific heat capacity being the most crucial. Existing literature has not fully elucidated the thermo-physical properties of binary and ternary molten salt nitrates through their operating temperature range. This work presents the viscosity of eutectic ternary and binary compositions of molten alkali salt nitrates (Li-NO3, K-NO3, and Na-NO3) up to 550°C. A device to measure the thermal conductivity of these salts with accuracy at elevated temperatures was designed and built as no commercial offerings are able to withstand the corrosive nature of molten salt at high temperatures. The device is shown to accurately measure the thermal conductivity of water at room temperature. The present work is a step towards fully characterizing the thermo-physical properties of the aforementioned molten salts.