Heat capacity and viscosity of ternary carbonate nanofluids

Abstract

Recent studies have shown that eutectic salt mixtures show remarkable enhancement in heat capacity after nanoparticles are dispersed at small concentrations. The exact mechanism behind these heat capacity enhancements is still inconclusive. However, recent studies proposed that the enhancement could be associated with nucleation and grain growth of salt dendritic structures. To investigate the hypothesis, we synthesized several samples of ternary carbonate salt mixture doped with 1% alumina nanoparticles and thermally cycled them at various heating rates and cooled them back to the solid-state during the synthesis procedure. It can affect the nucleation/grain growth of salt dendritic nanostructures and, as a result, there can be different heat capacity enhancements. A differential scanning calorimetry was employed to characterize the heat capacity values of the systems. It was observed that the heat capacity enhancements decreased with increases in the heating rates. The highest heat capacity enhancement was observed at the lowest heating rate (ie, 2 C/min). A transmission electron microscope was employed to confirm the effect of heating cycling rates on the formation of dendritic structures. Moreover, pH variation method was used to study the effect of the dendritic structures on the heat capacity of the mixture. Furthermore, a rheometer was employed to characterize the rheological behavior. It was observed that nanofluid samples showed shear-thinning behavior, whereas shear thinning was not observed in pure and nanofluid prepared with the pH variation method.

Particle Technology in the Formulation and Fabrication of Thermal Energy Storage Materials

“…Recently, another theory attributes the enhancement in heat capacity to the formation of dendritic nanostructures (see Fig. 2) which was also experimentally observed by scanning electron microscopy (SEM) 18. The high specific surface energy of nanoparticles makes it easy to form nanostructures, leading to increased specific heat of the molten salt nanocomposite.…”

“…Figure2. Nucleation and the grain growth of a dendritic structure in a molten salt nanofluid (reproduced from[18] with permission from Wiley).…”

Thermal Analysis of Magneto-Natural Convection Flows within a Partially Thermally Active Rectangular Enclosure

“…The creation of such a composite nanofluid is innovative since it significantly enhances thermophysical and heat transfer properties. Experimental studies show that these fluids' thermal conductivities are higher than those of hybrid and mono nanofluids [14,15].…”

Effects of interface layer on the thermophysical properties of solar salt‐SiO 2 nanofluids: A molecular dynamics simulation

“…22,25 Shin et al 15 first proposed three models affecting the SHC of MSBNFs as follows: (a) the high surface energy of nanoparticle; (b) interfacial interactions between nanoparticle and the adhering liquid molecules; (c) the semi-solid liquid layer adhering to the nanoparticles. In recent research, Shin et al 14,16,26 pointed out that the nanostructure between nanoparticle and molten salt changed the structure of the base molten salt, which was used to explain the enhancements in the thermophysical properties. Xiong et al 27 dispersed 20 nm SiO 2 nanoparticles into solar salt (60 wt% NaNO 3 /40 wt% KNO 3 ), and proposed the molten salt molecules are adsorbed to the nanoparticle surface layer by layer may be the main reason for the thermal performance enhancement of the MSBNFs.…”