化工进展 ›› 2019, Vol. 38 ›› Issue (11): 4865-4872.DOI: 10.16085/j.issn.1000-6613.2019-0326

• 化工过程与装备 • 上一篇    下一篇

粒径混合比对Al2O3/水纳米流体传热性能影响及评价

翟玉玲(),王江,李龙,马明琰,姚沛滔   

  1. 昆明理工大学冶金与能源学院,省部共建复杂有色金属重点实验室,云南 昆明 650093
  • 收稿日期:2019-03-06 出版日期:2019-11-05 发布日期:2019-11-05
  • 通讯作者: 翟玉玲
  • 作者简介:翟玉玲(1986—),女,博士,副教授,硕士生导师,研究方向为中低温余热高效利用。E-mail:zhaiyuling00@126.com
  • 基金资助:
    国家自然科学基金青年项目(51806090)

Evaluation and effect of mixture ratio on heat transfer performance of Al2O3/water nanofluids

Yuling ZHAI(),Jiang WANG,Long LI,Mingyan MA,Peitao YAO   

  1. State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization, Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093, Yunnan, China
  • Received:2019-03-06 Online:2019-11-05 Published:2019-11-05
  • Contact: Yuling ZHAI

摘要:

采用两步法制备体积分数为0.5%和1.0%的Al2O3/水纳米流体,研究20nm和50nm Al2O3纳米粒子的混合比对热导率和黏度的影响,并用c μ/c λ和Mo数来评价其综合传热效果,判断是否适用于实际传热过程。实验结果表明,有效热导率和相对黏度受团聚体尺寸影响较大。在体积分数为1.0%和混合比为50∶50时有效热导率的增幅最大,而混合比为(40∶60)~(60∶40)之间,相对黏度最低。这是因为此时团聚体的尺寸小,相应地沉淀速度慢,说明其分散性较好,形成局部粒子富集区,即“50nm固体粒子-20nm固体粒子-液体分子”的界面层,能产生高导热渗透通道及低热阻区,使热导率增大。在层流时,该纳米流体适用于实际传热过程中的范围为:体积分数0.5%和1.0%,混合比40∶60和50∶50,温度25~50℃。在紊流时,体积分数为0.5%和温度高于40℃时,混合比范围为(40∶60)~(60∶40)才适合使用此纳米流体。

关键词: 纳米流体, 热导率, 黏度, 团聚体尺寸, 混合比

Abstract:

A two-step method was used to prepare Al2O3/water of nanofluids at mass fraction of 0.5% and 1.0%. This work focuses on the effect of mixture ratio of 20nm and 50nm Al2O3 nanoparticles on the thermal conductivity and viscosity. Moreover, the comprehensive heat transfer of Al2O3/water of nanofluids was estimated by c μ/c λ and Mo in the real heat transfer process. The experimental results showed that the effect of the cluster size on effective thermal conductivity and viscosity is obvious. Al2O3/water of nanofluids with mass fraction of 1.0% and mixture ratio of 50∶50 exhibited the largest enhancement of effective thermal conductivity while the relative viscosity was the lowest with mixture ratio from 40∶60 to 60∶40. The reason is that the smaller clustering size of order enables nanofluids to reduce sedimentation rate indicating the dispersion of nanofluids. Thus, the formation of a localized particle-rich zone creates high-conductive percolation path of lesser thermal resistance compared to a particle-free zone, which forms “50nm-20nm-liquid layered structure” and results in enhancing thermal conductivity. Lastly, the suitable areas for nanofluids applied in laminar flow were the temperature range from 25℃ to 50℃ and mixture ratio of 40∶60 and 50∶50 at mass fraction of 0.5 % and 1.0%. Moreover, the suitable areas for nanofluids applied in turbulent flow were the mixture ratio range from 40∶60 to 60∶40 and temperature higher than 40℃ at mass fraction of 0.5 %.

Key words: nanofluids, thermal conductivity, viscosity, cluster size, mixture ratio

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