碳纳米管及纳米氧化铝对硝酸盐相变材料热性能的影响

doi:10.12028/j.issn.2095-4239.2018.0039

摘要/Abstract

摘要： 硝酸熔融盐具有良好的热物性能，在聚光太阳能发电技术中得到广泛运用，通过提高熔盐的比热容，可以提高其蓄热能力。将硝酸锂、硝酸钾和硝酸钠以共晶比52：30：18制备硝酸盐储热材料，通过添加纳米氧化铝颗粒及碳纳米管研究其对熔融盐比热的影响。通过超声振动和蒸发在硝酸熔融盐中加入纳米氧化铝颗粒和碳纳米管。采用直接合成法制备含纳米氧化铝和碳纳米管分别为0.06%、0.5%、1%和2%的硝酸盐纳米流体。通过SEM观察了纳米氧化铝颗粒及碳纳米管在硝酸盐中的分散性，当纳米氧化铝颗粒浓度为1%时发生团聚，这种团聚会影响纳米流体的比热容。碳纳米管添加量小于2%时分散性好。通过差示扫描量热仪（DSC）测量了硝酸盐纳米复合材料的比热容，纳米氧化铝浓度为1%的硝酸盐纳米流体在固态（110℃）和液态（140℃）下分别是纯硝酸盐比热容的1.44倍和3.48倍。CNTs浓度为1%的硝酸盐纳米流体在固态（110℃）和液态（140℃）下分别是纯硝酸盐比热容的5.07倍和4.17倍。DSC结果表明当纳米颗粒浓度大于1%时，纳米流体的比热降低。本研究讨论了提高纳米流体比热容的机制，得到硝酸盐比热容的增加与纳米颗粒的高比表面积和高能量相关。

关键词: 纳米氧化铝, 碳纳米管, 比热容, 硝酸盐, 相变材料

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

中图分类号:

TK02

MEHVISH Tariq, 程晓敏, 李元元, 黄毅, 李戈, 王秀丽, 朱石磊, WAQAR Khan. 碳纳米管及纳米氧化铝对硝酸盐相变材料热性能的影响[J]. 储能科学与技术, 2018, 7(S1): 47-53.

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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