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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.
The spherical ZnO nanoparticles with regular shape and uniform particle diameter were formed by hydrothermal method and dispersed in water ultrasonically to prepare a stable water-based ZnO nanofluid. The conductivity of water-based ZnO nanofluids was measured in volume fraction and temperature And the thermal conductivity of water-based ZnO nanofluids at different volume fractions at room temperature was tested.The experimental results show that the addition of ZnO nanoparticles greatly improves the thermal conductivity and conductivity of the water-based (pure water), water-based ZnO The conductivity of nanofluids increases nonlinearly with the increase of volume fraction of nanoparticles, while the conductivity shows a quasi-linear relationship with the temperature change. The thermal conductivity of nanofluids increases approximately linearly with the increase of nanoparticle volume fraction. Maxwell thermal conductivity model and Brown’s kinetic theory, and considering the influence of adsorption layer, agglomerate and Brownian motion on the thermal conductivity, a thermal conductivity correction model is proposed.Compared with the experimental data The results show that the modified model can calculate the thermal conductivity of nanofluids more accurately.