Thermal properties enforcement of carbonate ternary via lithium fluoride: A heat transfer fluid for concentrating solar power systems

A novel eutectic of Li 2 CO 3 -Na 2 CO 3 -K 2 CO 3 improved by LiF, when employed as a heat transfer fluid in concentrating solar power systems, is prepared to eliminate the disadvantage of limited operating temperature range and low specific heat as well as thermal conductivity . Using the static melting method, Li 2 CO 3 -Na 2 CO 3 -K 2 CO 3 with 15.0 wt.% LiF which is simply physical mixture determined by X-ray diffraction, is chosen as the optimized candidate. Results indicate that, at 10 °C/min of heating rate , LiF-Li 2 CO 3 -Na 2 CO 3 -K 2 CO 3 reached melting point of 368 °C and upper temperature limit of 753 °C, allowing it to be effectively employed in thermal storage and heat transfer in high temperature CSP systems. During temperature range from 400 to 600 °C, the liquid quaternary exhibited notably mean specific heat of 1.917 J/(g·°C), which is larger than that of the original ternary eutectic. Thermal conductivity of solid LiF-Li 2 CO 3 -Na 2 CO 3 -K 2 CO 3 reached the stable level of 1.021 W/(m·°C) at 320 °C. Density of improved eutectic tested by the archimedean principle is approximately 1.95 g/cm 3 . In conclusion, LiF-Li 2 CO 3 -Na 2 CO 3 -K 2 CO 3 can be employed as the admirable heat transfer fluid for thermal storage and heat transfer in high-temperature CSP plants. This investigation will provide useful information for further improvement of molten salt based heat transfer fluids.