碳纳米管-导热油纳米流体导热与流变特性研究

Thermal and Rheological Properties of Carbon Nanotubes-Oil Nanofluid

纳米流体作为新型换热工质,是强化传热的有效途径。今用两步法制备碳纳米管-导热油纳米流体,实验研究流变及导热性能,分析碳纳米管长短、体积分数、温度、转速、SN比(活性剂与纳米颗粒质量比)等因素的影响。结果表明,导热率和黏度随体积分数提高而增大,但随温度升高而下降;碳纳米管长度短,黏度小;长度长,导热率高;体积分数为7%时,导热率提高50%。本研究制备流体都为假塑性流体,低转速下,黏度随SN比先减小后增大;导热率H-C模型中,形状因子n取7时与实验数据基本吻合,并据此提出适合本研究的导热率修正公式。

As a novel heat transfer medium, nanofluid is effective to strengthen heat transfer. We prepared carbon nanotubes-oil nanofluid with two-step method, and analyzed the influence of the nanotube length, volume fraction, temperature, rotate speed, SN ratio （the mass ratio of surfactant and nanoparticles） and other factors on the thermal and theological properties. The results show that, thermal conductivity and viscosity of nanofluid increase with the increasing of volume fraction of the nanotubes while decrease with the rising of temperature. The thermal conductivity of long carbon nanotubes-oil nanofluid is relatively high and the viscosity of short carbon nanotubes-oil nanofluid is relatively low. The nanofluids prepared are pseudoplastic fluid, and at low rotational speed, viscosity decreases with SN ratio increasing firstly but increases latterly, and there exists the optimum SN ratio of 0.4, which makes the viscosity least. In the experiment, the thermal conductivity was increased by 50% at maximum with 7%（vol） carbon nanotubes and the result fits well with model of H-C when the shape factor n is taken to be 7.