Abstract
An anomalous increase of the specific heat was experimentally observed in molten salt nanofluids using a differential scanning calorimeter. Binary carbonate molten salt mixtures were used as a base fluid, and the base salts were doped with graphite nanoparticles. Specific heat measurements of the nanofluids were performed to examine the effects of the composition of two salts consisting of the base fluid. In addition, the effect of the nanoparticle concentration was investigated as the concentration of the graphite nanoparticles was varied from 0.025 to 1.0 wt %. Moreover, the dispersion homogeneity of the nanoparticles was explored by increasing amount of surfactant in the synthesis process of the molten salt nanofluids. The results showed that the specific heat of the nanofluid was enhanced by more than 30% in the liquid phase and by more than 36% in the solid phase at a nanoparticle concentration of 1 wt %. It was also observed that the concentration and the dispersion homogeneity of nanoparticles favorably affected the specific heat enhancement of the molten salt nanofluids. The dispersion status of graphite nanoparticles into the salt mixtures was visualized via scanning electron microscopy. The experimental results were explained according to the nanoparticle-induced compressed liquid layer structure of the molten salts.
Highlights
Nanofluids have attracted considerable attention in heat-transfer fields because of their enhanced thermal properties, such as their thermal conductivity and boiling characteristics
The results showed that the specific heat of the nanofluid was enhanced by more than 30% in the liquid phase and by more than 36% in the solid phase at a nanoparticle concentration of 1 wt %
It was observed that the concentration and the dispersion homogeneity of nanoparticles favorably affected the specific heat enhancement of the molten salt nanofluids
Summary
Nanofluids have attracted considerable attention in heat-transfer fields because of their enhanced thermal properties, such as their thermal conductivity and boiling characteristics. In the early 2000s, the dramatic increase of the critical heat flux in pool boiling of nanofluids gave rise to the consideration of nanofluids as an alternative to conventional heat-transfer fluids [3,4] After those publications, related studies into the thermal property and boiling characteristic have been actively performed under various experimental conditions. Dr Banerjee’s research groups reported that the specific heat of binary molten salt mixtures (or eutectic), which are considered as thermal energy storage media in concentrating solar power plants, can be enhanced via doping with nanoparticles. They used various molten salts (carbonate salts, nitrate salts, and chloride salts) as base fluids, along with both organic and inorganic nanoparticles. The experimental results obtained in this study helps us in understanding quantitative effects of each parameter on enhancing specific heat of the molten salt mixture by doping with the nanoparticles
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