View in EDS

Study of viscosity and heat capacity characteristics of molten salt nanofluids for thermal energy storage.

Saved in:
Bibliographic Details
Title: Study of viscosity and heat capacity characteristics of molten salt nanofluids for thermal energy storage.
Authors: El Far, Baha1 (AUTHOR), Rizvi, Syed Muhammad Mujtaba1 (AUTHOR), Nayfeh, Yousof1 (AUTHOR), Shin, Donghyun1 (AUTHOR) shin1d@cmich.edu
Source: Solar Energy Materials & Solar Cells. Jun2020, Vol. 210, pN.PAG-N.PAG. 1p.
Subjects: Heat capacity, Nanofluids, Fused salts, Heat storage, Pseudoplastic fluids, Viscosity, Electron microscopes, Binary mixtures
Abstract: In this study, we synthesized molten salt nanofluids by dispersing spherical SiO 2 nanoparticles at a minute concentration (1 wt%) into a binary mixture of NaNO 3 -KNO 3. The results showed that the heat capacity was enhanced by 15% and the viscosity was enhanced by 41–429%. Moreover, the nanofluids have shown significant non-Newtonian behavior (shear thinning). Nanofluids are known to show non-Newtonian behavior when particles have high aspect ratio (e.g., nanotube, rod-like structure) at high concentrations; however, only spherical nanoparticles were dispersed in molten salt at an extremely low concentration (1 wt%). The observed enhancement in heat capacity and the shear thinning behavior could result from the formation of dendritic salt nanostructures. Hence, we added hydroxide at an extremely low concentration (0.03 wt%) to disrupt the formation of such dendritic nanostructures to confirm their effects on the heat capacity and shear thinning behavior. The result showed that the heat capacity enhancement diminished from 15% to 3%. Moreover, the viscosity enhancement decreased from 429% to 148% at low shear rate (10/s) and from 41% to 10% at high shear rate (240/s). Furthermore, the enhanced viscosity of 10% at the highest shear rate (240/s), where the effect of the dendritic nanostructures is minimal, agreed well with a theoretical model developed for the viscosity of a simple liquid doped with nanoparticles. It supports that the dendritic salt nanostructures are primarily responsible for the enhanced heat capacity and the shear-thinning behavior of molten salt nanofluids. Material characterization using an electron microscope confirmed the presence of the dendritic salt nanostructures. • We synthesized molten salt nanofluids by dispersing SiO 2 nanoparticles at a minute concentration (1 wt%) into a binary mixture of NaNO 3 -KNO 3. • The heat capacity and the viscosity were enhanced by 15% and 41–429%, respectively. A non-Newtonian behavior (shear thinning) was observed. • We added hydroxide at an extremely low concentration (0.03 wt%) to disrupt the formation of such dendritic nanostructures. • The heat capacity and viscosity enhancements decreased from 15 % to 3 % and from 41-429% to 10-148%, respectively. • It supports that the dendritic salt nanostructures are responsible for the enhanced heat capacity and the shear-thinning behavior. [ABSTRACT FROM AUTHOR]
Copyright of Solar Energy Materials & Solar Cells is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
Database: Engineering Source
Description
Abstract:In this study, we synthesized molten salt nanofluids by dispersing spherical SiO 2 nanoparticles at a minute concentration (1 wt%) into a binary mixture of NaNO 3 -KNO 3. The results showed that the heat capacity was enhanced by 15% and the viscosity was enhanced by 41–429%. Moreover, the nanofluids have shown significant non-Newtonian behavior (shear thinning). Nanofluids are known to show non-Newtonian behavior when particles have high aspect ratio (e.g., nanotube, rod-like structure) at high concentrations; however, only spherical nanoparticles were dispersed in molten salt at an extremely low concentration (1 wt%). The observed enhancement in heat capacity and the shear thinning behavior could result from the formation of dendritic salt nanostructures. Hence, we added hydroxide at an extremely low concentration (0.03 wt%) to disrupt the formation of such dendritic nanostructures to confirm their effects on the heat capacity and shear thinning behavior. The result showed that the heat capacity enhancement diminished from 15% to 3%. Moreover, the viscosity enhancement decreased from 429% to 148% at low shear rate (10/s) and from 41% to 10% at high shear rate (240/s). Furthermore, the enhanced viscosity of 10% at the highest shear rate (240/s), where the effect of the dendritic nanostructures is minimal, agreed well with a theoretical model developed for the viscosity of a simple liquid doped with nanoparticles. It supports that the dendritic salt nanostructures are primarily responsible for the enhanced heat capacity and the shear-thinning behavior of molten salt nanofluids. Material characterization using an electron microscope confirmed the presence of the dendritic salt nanostructures. • We synthesized molten salt nanofluids by dispersing SiO 2 nanoparticles at a minute concentration (1 wt%) into a binary mixture of NaNO 3 -KNO 3. • The heat capacity and the viscosity were enhanced by 15% and 41–429%, respectively. A non-Newtonian behavior (shear thinning) was observed. • We added hydroxide at an extremely low concentration (0.03 wt%) to disrupt the formation of such dendritic nanostructures. • The heat capacity and viscosity enhancements decreased from 15 % to 3 % and from 41-429% to 10-148%, respectively. • It supports that the dendritic salt nanostructures are responsible for the enhanced heat capacity and the shear-thinning behavior. [ABSTRACT FROM AUTHOR]
ISSN:09270248
DOI:10.1016/j.solmat.2020.110503