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利用水热法生成了形状规则、粒径均匀的球形ZnO纳米颗粒, 并超声分散于水中, 制备得到稳定的水基ZnO纳米流体. 实验测量水基ZnO纳米流体在体积分数和温度变化时的电导率, 并测试室温下水基ZnO纳米流体在不同体积分数下的热导率. 实验结果表明, ZnO纳米颗粒的添加较大地提高了基液(纯水)的热导率和电导率, 水基ZnO纳米流体的电导率随纳米颗粒体积分数增加呈非线性增加关系, 而电导率随温度变化呈现出拟线性关系; 纳米流体的热导率与纳米颗粒体积分数增加呈近似线性增加关系. 本文在经典Maxwell热导模型和布朗动力学理论的基础上, 同时考虑了吸附层、团聚体和布朗运动等因素对热导率的影响, 提出了热导率修正模型.将修正模型预测值与实验值对比, 结果表明修正模型可以较为准确地计算出纳米流体的热导率.Spherical ZnO nanoparticles each with a uniform size are synthesized by a hydrothermal method. These ZnO nanoparticles are then dispersed into water by ultrasonic vibrating to form stable nanofluids. The electrical conductivity of water-based ZnO nanofluids with a variety of temperature and volumetric fractions are investigated. The volumetric-fraction-dependent thermal conductivity is also measured at room temperature. Experiments indicate that the electrical conductivity of ZnO nanofluid reveals a non-linear relationship versus volumetric fraction. However, it presents a quasi linear relationship versus temperature. The thermal conductivity is enhanced nearly linearly with volumetric fraction increasing. Moreover, a modified model is established based on Maxwell thermal conductivity model and Brownian dynamics theory by considering boundary adsorption layer, aggregation and Brownian motion of nanoparticles in the fluid. The expected thermal conductivity values based on the modified model are in good agreement with our experimental data, suggesting that our modified model might be more accurately adapted to the nanofluids thermal conductivity.
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Keywords:
- hydrothermal method /
- electrical conductivity /
- thermal conductivity /
- thermal conductivity model
[1] Das S K, Choi S U S, Patel H 2006 Heat Transfer Eng. 27 3
[2] Li Y J, Zhou J E, Tung S, Schneider E, Xi S Q 2009 Powder Technol. 196 89
[3] Xie H Q, Chen L F 2009 Acta Phys. Sin. 58 2513 (in Chinese) [谢华清, 陈立飞 2009 58 2513]
[4] Choi S U S, Siginer D A, Wang H P 1995 Developments and Applications of non-Newtonian Flows (New York: The American Society of Mechanical Engineers) p99
[5] Saidura R, Leongb K Y, Mohammadc H A 2011 Renew. Sust. Energ. Rev. 15 1646
[6] Shen L P, Wang H, Dong M, Ma Z C, Wang H B 2012 Phys. Lett. A 376 1053
[7] Saleh R, Putra N, Prakoso S P, Septiadi W N 2013 Int. J. Therm. Sci. 63 125
[8] Lee G J, Kim C K, Lee M K, Rhee C K, Kim S, Kim C 2012 Thermochim. Acta 542 24
[9] Yu W, Xie H Q, Chen L F, Li Y 2009 Thermochim. Acta 491 92
[10] Suganthi K S, Rajan K S 2012 Asian J .Sci. Res. 5 207
[11] Hong J, Kim S H, Kim D 2007 J. Phys. 59 301
[12] Zhang L L, Ding Y L, Povey M 2008 Prog. Nat. Sci. 18 939
[13] Shen L P 2012 Ph. D. Dissertation (Wuhan: Huazhong University of Science and Technology) (in Chinese) [沈谅平 2012 博士学位论文 (武汉: 华中科技大学)]
[14] Jiang W T 2009 Ph. D. Dissertation (Shanghai: Shanghai Jiao Tong University) (in Chinese) [姜未汀 2009 博士学位论文(上海: 上海交通大学)]
[15] Maxwell J C 1981 A Treatise on Electricity and Magnetism (Oxford: Clarendon Press) p440
[16] Xie H Q, Xi T G, Wang J C 2003 Acta Phys. Sin. 52 1444 (in Chinese) [谢华清, 奚铜庚, 王锦昌 2003 52 1444]
[17] Yu W, Choi S 2003 J. Nanopart. Res. 5 167
[18] Xuan Y M, Li Q, Hu W F 2003 AICHE J. 49 1038
[19] Ding G L, Jiang W T, Peng H, Hu H T 2010 J. Eng. Thermophys. Rus. 31 1281 (in Chinese) [丁国良, 姜未汀, 彭 浩, 胡海涛 2010工程热 31 1281]
[20] Wang B X, Zhou L Z, Peng X F 2003 Int. J. Heat Mass Trans. 46 2665
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[1] Das S K, Choi S U S, Patel H 2006 Heat Transfer Eng. 27 3
[2] Li Y J, Zhou J E, Tung S, Schneider E, Xi S Q 2009 Powder Technol. 196 89
[3] Xie H Q, Chen L F 2009 Acta Phys. Sin. 58 2513 (in Chinese) [谢华清, 陈立飞 2009 58 2513]
[4] Choi S U S, Siginer D A, Wang H P 1995 Developments and Applications of non-Newtonian Flows (New York: The American Society of Mechanical Engineers) p99
[5] Saidura R, Leongb K Y, Mohammadc H A 2011 Renew. Sust. Energ. Rev. 15 1646
[6] Shen L P, Wang H, Dong M, Ma Z C, Wang H B 2012 Phys. Lett. A 376 1053
[7] Saleh R, Putra N, Prakoso S P, Septiadi W N 2013 Int. J. Therm. Sci. 63 125
[8] Lee G J, Kim C K, Lee M K, Rhee C K, Kim S, Kim C 2012 Thermochim. Acta 542 24
[9] Yu W, Xie H Q, Chen L F, Li Y 2009 Thermochim. Acta 491 92
[10] Suganthi K S, Rajan K S 2012 Asian J .Sci. Res. 5 207
[11] Hong J, Kim S H, Kim D 2007 J. Phys. 59 301
[12] Zhang L L, Ding Y L, Povey M 2008 Prog. Nat. Sci. 18 939
[13] Shen L P 2012 Ph. D. Dissertation (Wuhan: Huazhong University of Science and Technology) (in Chinese) [沈谅平 2012 博士学位论文 (武汉: 华中科技大学)]
[14] Jiang W T 2009 Ph. D. Dissertation (Shanghai: Shanghai Jiao Tong University) (in Chinese) [姜未汀 2009 博士学位论文(上海: 上海交通大学)]
[15] Maxwell J C 1981 A Treatise on Electricity and Magnetism (Oxford: Clarendon Press) p440
[16] Xie H Q, Xi T G, Wang J C 2003 Acta Phys. Sin. 52 1444 (in Chinese) [谢华清, 奚铜庚, 王锦昌 2003 52 1444]
[17] Yu W, Choi S 2003 J. Nanopart. Res. 5 167
[18] Xuan Y M, Li Q, Hu W F 2003 AICHE J. 49 1038
[19] Ding G L, Jiang W T, Peng H, Hu H T 2010 J. Eng. Thermophys. Rus. 31 1281 (in Chinese) [丁国良, 姜未汀, 彭 浩, 胡海涛 2010工程热 31 1281]
[20] Wang B X, Zhou L Z, Peng X F 2003 Int. J. Heat Mass Trans. 46 2665
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