Abstract:

A 3ω method was developed for the simultaneous determination of thermal conductivity and thermal diffusivity of nanofluidsThe principle was presented in the frequency domainThe 3ω system was established by using a Pt wire as the heater and sensorThe system was calibrated by using water with known propertiesThe thermal oscillation signals satisfied the heat conduction equations well in frequency domainIt showed that the microconvection effect of the liquid could be reduced effectively by periodical heatingThe multispherical Brownian motion(MSBW) model was used to predict the thermal conductivities of nanofluidsThe thermal conductivity and thermal diffusivity of TiO2/water and Al₂O₃/water at different temperatures were proved to increase linearly with the temperature at a low volume fractionThe results showed that temperature dependence played an important role in the enhancement of thermal transport in nanofluidsAt 18—65℃，the enhancement of heat transfer for nanofluids was mainly due to the thermal conductivity increment of water and the microconvection effect.

Key words:

3ω法, 纳米流体, 热导率, 热扩散系数, 微对流模型

摘要：

提出了应用基于谐波探测技术的3ω法进行液体导热性能测量的方法。设计了3ω测试系统，测试了不同浓度和不同温度下纳米流体的热导率和热扩散系数，与文献中的测试结果进行了对比。实验中测试的热波信号较好地满足频域内的导热方程，说明采用交流电流加热可使流体的微对流作用得到有效减弱。采用基于多颗粒布朗运动的微对流（MSBW）模型预测了纳米流体的热导率。浓度比较低时TiO₂+蒸馏水、Al₂ O₃+蒸馏水纳米颗粒流体的热导率随温度增加呈线性增大，并且与液体的Prandtl数有关，在测试温度为18～65℃范围内，水的热导率随温度升高以及纳米颗粒的布朗运动所引起周围基液的微对流作用是纳米流体强化传热的两个重要机理。

关键词:

3ω法, 纳米流体, 热导率, 热扩散系数, 微对流模型