DeFilippo, Anthony C. , ZURITA GOTOR, MAURICIO, Durth, Melanie , Fereres, Sonia
No
J Mol Liq
Article
Científica
6.165
0.929
15/05/2020
000534192100044
2-s2.0-85082167788
Binary alkali nitrate molten salts are currently the heat transfer fluid\n (HTF) and thermal energy storage (TES) media of choice in commercial\n solar thermal energy (STE) power plants. This paper studies the\n rheological properties of binary alkali nitrate molten salts containing\n two distinct classes of suspended particles with unique practical\n applications and dynamics. Phase change salt slurries (liquid/solid\n suspensions) can appear during plant start-up after local freezing in\n pipes. Molten salt-nanopartide suspensions are being proposed in the\n literature as an advanced HIP with enhanced properties. The phase change\n slurries were analyzed by rheological measurement of off-eutectic salt\n mixtures at sub-liquidus temperatures combined with determination of\n solid fraction through differential scanning calorimeter (DSC) testing\n in a novel approach. Molten salts with a range of silica nanoparticle\n loadings were also studied in the rheometer. Both suspension types\n exhibit non-Newtonian, shear thinning behavior, with a dramatic increase\n in viscosity compared to the base fluid. Additionally, both suspension\n types show that measured viscosity depends on the shear history, but the\n trends in viscosity with shear history differs between the two systems.\n The increase in viscosity with solid volume fraction of the nanofluid is\n significantly higher than that of a partially-crystallized salt slurry\n at a given volume fraction. Particle aggregation, particle/cluster\n aspect ratio, cluster breakage and restructuring are considered as\n determining factors in the observed rheological behavior. Deviations\n from classical effective medium theories of well-dispersed systems are\n discussed. Differing trends suggest that unique physical phenomena\n govern the rheological behaviors of the molten salt mixtures with\n different suspended solid particles. Thus, engineers and scientists must\n exercise caution when extrapolating rheological results to unique\n applications. (C) 2018 Elsevier B.V. All rights reserved.
Viscosity; Molten salts; Nitrates; Two-phase mixtures; Nanofluids