Thermal property characterization of a low melting-temperature ternary nitrate salt mixture for thermal energy storage systems

Molten salts have better thermal properties than synthetic mineral oil, and hence they can be directly used as heat transfer fluids in solar power plants, but in practice their direct applications as heat transfer fluids are constrained due to their high freezing temperature points. In this paper, a class of ternary nitrate salt mixtures consisting of 50–80 wt% KNO3, 0–25 wt% LiNO3 and 10–45 wt% Ca(NO3)2 were processed and tested. Experimental results indicated that some mixtures within this range exhibited excellent thermal properties, such as a low melting point (<100 °C), robust reliability, high-temperature stability (upto 500 °C) and a low viscosity (e.g.,<5 cP at 190 °C). Apart from these desirable thermo-physical properties, the manufacturing cost of these novel inorganic salts HTFs (Heat Transfer Fluids) is considerably lower than those of the existing commercial heat transfer fluids (HTFs).

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► A novel ternary salt mixture with the low melting temperature below 100 °C.
► Ternary salt consists of KNO3, LiNO3 and Ca(NO3)2.
► Its overall thermal properties advantageous compared to those of commonly used HTFs.
► Viscosity less than 10 cP in the main operation temperature range.