Influence of carbon nanotubes and nano-alumina on the thermal performance of nitrate phase change materials for thermal storage

doi:10.12028/j.issn.2095-4239.2018.0039

Abstract

Abstract: Nitrate molten salts have earned a lot of fame in concentrating solar power plants due to its better thermophysical properties. Thermal storage capacity of a molten salt can be improved by increasing its specific heat capacity. This study investigate the influence on the specific heat capacity by adding alumina nanoparticles and carbon nanotubes to the eutectic mixture of lithium nitrate, potassium nitrate and sodium nitrate by percentage ratios of 52:30:18. Alumina and CNTs were added with concentration of 0.06%, 0.5%, 1%, 2% for each. Molten salt based nanofluid was developed by using direct synthesis method i-e nanoparticles were added in the salts mixture followed by ultra-sonication and evaporation. The microstructures were observed using scanning electron microscope (SEM) to reveal the dispersion of the nanoparticles. SEM analysis shows that as the concentration of nanoparticles increases it starts to agglomerates and form clusters. This type of agglomeration affects the specific heat capacity of nanofluid. Specific heat capacity was measured using the differential scanning calorimeter (DSC). The DSC results of alumina based nanofluid shows the 1.44 times enhancement of specific heat capacity at solid state (110℃) and 3.48 times at liquid state (140℃). Similarly, for CNTs there is 5.07 times enhancement of specific heat capacity at solid state (110℃) and 4.17 times at liquid state (140℃). These DSC results are shown at 1% concentration of nanoparticles after this concentration the C_p for the nanofluid decreased. This research discussed the mechanisms involved in enhancement of specific heat capacity of nanofluid. It is concluded that high specific energies related with the high specific surface area of the nanoparticles can be responsible for the observed enhancement in the specific heat capacity.

Key words: alumina nanoparticles, CNTS, specific heat capacity, lithium nitrate, phase change materials

CLC Number:

TK02

MEHVISH Tariq, CHENG Xiaomin, LI yuanyuan, HUANG Yi, LI Ge, WANG Xiuli, ZHU Shilei, WAQAR Khan. Influence of carbon nanotubes and nano-alumina on the thermal performance of nitrate phase change materials for thermal storage[J]. Energy Storage Science and Technology, 2018, 7(S1): 47-53.

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