Enhanced thermal properties of Li2CO3–Na2CO3–K2CO3 nanofluids with nanoalumina for heat transfer in high-temperature CSP systems

Abstract

Nanofluids of Li2CO3–Na2CO3–K2CO3 improved by three nano-Al2O3 samples are firstly prepared by means of two-step aqueous method to enhance thermal properties for high-temperature heat transfer, when used as heat transfer fluids and thermal energy systems for concentrating solar power systems. Specific heat of ternary carbonates containing Al2O3 of 0.2, 0.4, 0.8, 1.0, 1.4 and 2.0 mass% is measured, and nanofluids with 1.0 mass% of 20-nm Al2O3, 1.0 mass% of 50-nm Al2O3 and 0.8 mass% of 80-nm Al2O3 are selected as superior candidates. The maximum enhancement of specific heat is 18.5% in solid and 33.0% in liquid, 17.9% in solid and 22.7% in liquid, 13.2% in solid and 17.5% in liquid for nanofluids containing 20-, 50- and 80-nm Al2O3. Thermal conductivity is, respectively, improved by 23.3, 28.5 and 30.9% under the addition of Al2O3. New chemical bonds and crystals are scarcely formed in composites through FT-IR and XRD determination. SEM images certify that nano-Al2O3 are homogeneously mixed into nanofluids and this structure may be a critical incentive for enhancing thermal properties. There are no significant changes with respect to the heat flow, melting/freezing point and latent heat after the 30 circles of determination. Briefly, it can be speculated that these nanofluids will exhibit tremendous potential in the coming applications of heat transfer and thermal storage for concentrating solar power systems.