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。
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.
作者
李昭
李宝让
崔柳
杜小泽
LI Zhao;LI Baorang;CUI Liu;DU Xiaoze(Key Laboratory of Power Station Energy Transfer Conversion and System(North China Electric Power University),Ministry of Education;School of Energy Power and Mechanical Engineering,North China Electric Power University,Beijing 102206,China;School of Energy and Power Engineering,Lanzhou University of Technology,Lanzhou 730050,Gansu,China)
出处
《储能科学与技术》
CAS
CSCD
2020年第6期1775-1783,共9页
Energy Storage Science and Technology
基金
国家自然科学基金项目(51676069,51821004)
中央高校基本科研业务费(2018QN034)。
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
molten salt
nanofluid
stability
specific heat capacity
preparation method
hybrid nanoparticle
作者简介
第一作者: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;联系人:杜小泽,教授,主要研究方向为强化传热、节能原理、储热,E-mail:duxz@ncepu.edu.cn;李宝让,教授,主要研究方向为储热材料、新型功能材料、结构陶瓷,E-mail:libr@ncepu.edu.cn。
