Anomalous Increase in Specific Heat of Binary Molten Salt-Based Graphite Nanofluids for Thermal Energy Storage
Abstract
:1. Introduction
2. Nanofluid Synthesis and Specific Heat Measurements
2.1. Materials
2.2. Synthesis of Nanofluids
2.3. Specific Heat Measurements
2.4. Uncertainty Analysis
3. Results and Discussion
4. Conclusions
- (a)
- The specific heat was anomalously enhanced by up to >30% in the liquid phase and 36% in the solid phase via the dispersion of graphite nanoparticles. The enhancements were strongly dependent on the chemical composition of the base fluid: the increments, as well as the enhancements in the specific heat, increased when the chemical composition of the base fluid was far from the eutectic composition.
- (b)
- The specific heat increased with the concentration of the nanoparticles. A noticeable increase was observed at the nanoparticle concentration of 0.025 wt % for the base fluid including 75 mol % lithium carbonate and 25 mol % potassium carbonate. A critical concentration of nanoparticles was observed. For nanoparticle concentrations exceeding 0.1 wt %, the increment was negligible.
- (c)
- The specific heat enhancements increased as the amount of the surfactant (GA) increased from 1 to 5 wt %. Larger enhancements were measured for the nanofluids with 5 wt % GA, and the actual specific heat value was almost double that of the eutectic.
- (d)
- The homogeneous dispersion of the graphite nanoparticles was visually confirmed via SEM (secondary electron images and backscatter images) for the nanofluid after a DSC test. In the SEM images, the graphite nanoparticles were spherical, having smooth curvature (not disks), so it was presumed that special structures, nanoparticle-induced compressed liquid layer, were formed in the nanofluids. The SEM images conclusively proved that the dispersion homogeneity (quality) of the nanoparticles is due to the specific heat enhancements of the nanofluids.
Author Contributions
Acknowledgments
Conflicts of Interest
References
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Mole Fraction of Each Salt | Specific Heat in Liquid Phase [J/g·K] | ||
---|---|---|---|
Sample Name | Li2CO3 [mol %] | K2CO3 [mol %] | |
Sample 1 | 90 | 10 | 2.582 |
Sample 2 | 80 | 20 | 2.503 |
Sample 3 | 62 | 38 | 1.646 |
Sample 4 | 50 | 50 | 1.543 |
Sample 5 | 40 | 60 | 1.325 |
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Kim, H.J.; Jo, B. Anomalous Increase in Specific Heat of Binary Molten Salt-Based Graphite Nanofluids for Thermal Energy Storage. Appl. Sci. 2018, 8, 1305. https://doi.org/10.3390/app8081305
Kim HJ, Jo B. Anomalous Increase in Specific Heat of Binary Molten Salt-Based Graphite Nanofluids for Thermal Energy Storage. Applied Sciences. 2018; 8(8):1305. https://doi.org/10.3390/app8081305
Chicago/Turabian StyleKim, Hyun Jung, and Byeongnam Jo. 2018. "Anomalous Increase in Specific Heat of Binary Molten Salt-Based Graphite Nanofluids for Thermal Energy Storage" Applied Sciences 8, no. 8: 1305. https://doi.org/10.3390/app8081305