储能科学与技术 ›› 2020, Vol. 9 ›› Issue (6): 1775-1783.doi: 10.19799/j.cnki.2095-4239.2020-0133

• 储能材料与器件 • 上一篇    下一篇

高温熔盐基纳米流体热物性的稳定性研究

李　昭1(), 李宝让2(), 崔　柳1, 杜小泽3()   

  1. 1.电站能量传递转化与系统教育部重点实验室（华北电力大学）
    2.华北电力大学能源动力与机械工程学院，北京 102206
    3.兰州理工大学能源与动力工程学院，甘肃 兰州 730050
  • 收稿日期:2019-04-02 修回日期:2020-04-23 出版日期:2020-11-05 发布日期:2020-10-28
  • 通讯作者: 李宝让,杜小泽 E-mail:zhaoli@ncepu.edu.cn;libr@ ncepu.edu.cn;duxz@ ncepu.edu.cn
  • 作者简介:李昭(1993—)，男，博士研究生，主要研究方向为纳米流体、传热强化，E-mail：zhaoli@ncepu.edu.cn；
  • 基金资助:
    国家自然科学基金项目(51676069);中央高校基本科研业务费(2018QN034)

Stability of the thermal performances of molten salt-based nanofluid

Zhao LI1(), Baorang LI2(), Liu CUI1, Xiaoze DU3()   

  1. 1.Key Laboratory of Power Station Energy Transfer Conversion and System (North China Electric Power University), Ministry of Education
    2.School of Energy Power and Mechanical Engineering, North China Electric Power University, Beijing 102206, China
    3.School of Energy and Power Engineering, Lanzhou University of Technology, Lanzhou 730050, Gansu, China
  • Received:2019-04-02 Revised:2020-04-23 Online:2020-11-05 Published:2020-10-28
  • Contact: Baorang LI,Xiaoze DU E-mail:zhaoli@ncepu.edu.cn;libr@ ncepu.edu.cn;duxz@ ncepu.edu.cn

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摘要：

利用纳米颗粒可显著强化高温熔融盐的储热和热输运性能，但在实际应用中，面临纳米颗粒团聚导致的强化作用衰减。采用两步法配制了质量分数为1%的SiO2-Solar Salt纳米流体，并设置长时间高温保温工况，以比热容衰减幅度和样品微观结构为评价标准，探究两步法制备样品的稳定性。实验结果表明，两步法所制备样品的比热容提升幅度较为明显，但其稳定性较差，经长期高温保温工况后，比热容提升幅度衰减较为明显，且微观形貌显示其中SiO2纳米颗粒含量大幅减少。为探究改善高温熔盐基纳米流体稳定性的方法，本工作从纳米流体制备方法和纳米颗粒选材角度入手进行研究。选取高温熔融法制备相同样品，实验结果表明，其比热容提升幅度与两步法所制备样品相差不大，但经长期高温保温工况后，比热容提升幅度的衰减小于两步法所制备样品，SiO2纳米颗粒含量也有所提升，稳定性得以初步改善。在采用高温熔融法的基础上进一步研究，添加少量Al2O3、TiO2或CuO，与SiO2形成混合纳米颗粒以制备纳米颗粒总量1%的样品，实验结果表明Al2O3-SiO2混合纳米流体经过100 h高温保温工况后，比热容提升幅度的衰减率已缩小至6.1%，稳定性得到进一步的提升，而TiO2-SiO2、CuO-SiO2混合纳米流体样品经过高温保温工况已完全失去比热容提升能力，稳定性恶化。研究结果对提高熔盐基纳米流体稳定性、增强其实用性具有重大意义。

关键词: 熔融盐, 纳米流体, 稳定性, 比热容, 制备方法, 混合纳米颗粒

Abstract:

The performance of a molten salt-based nanofluid can be significantly enhanced, but its thermal stability caused by the nanoparticle cluster remains a main defect for practical application. This study prepared a solar salt-based SiO2 nanofluid with 1% mass fraction via a two-step method. To study the stability of the molten salt-based nanofluid, a long-term high-temperature (LTHT) condition is set, and the reduction of the specific heat capacity (SHC) enhancement and micro-morphology is adopted to make a comprehensive stability assessment. The experimental results show an SHC enhancement; however, the SHC is significantly decreased, and the SiO2 nanoparticle amount in the samples is reduced after the LTHT condition. In other words, the sample prepared by the two-step method is a poor-stability nanofluid. The investigation on the method improving the stability of the molten salt-based nanofluid is based on the preparation methods and the nanoparticle material selection. The high-temperature melting method is used to prepare the same nanofluid. The results show that the SHC enhancement is similar to that of the sample prepared by the two-step method; however, the SHC enhancement after the LTHT condition is slightly reduced with the nanoparticle amount increase. This result implies that the stability of the molten salt-based nanofluid can be improved to some extent using the high-temperature melting method. Hybrid nanofluids with total mass fraction of 1% (i.e., Al2O3-SiO2, TiO2-SiO2, and CuO-SiO2 nanofluids) are also investigated herein based on the high-temperature melting method. The results show that the attenuation rate of the SHC enhancement reduces to 6.1% after 100 h under the LTHT condition for the Al2O3-SiO2 hybrid nanofluid, indicating that the stability is further improved. On the contrary, the stability of the TiO2-SiO2 and CuO-SiO2 hybrid nanofluids is worse because no SHC enhancement occurs after the LTHT condition. The results are greatly significant for improving the stability of the molten salt-based nanofluid and enhancing its practicality.

Key words: molten salt, nanofluid, stability, specific heat capacity, preparation method, hybrid nanoparticle

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