纳米流体导热系数研究

用热丝法测量了分别由氧化铝纳米粉体和碳纳米管加入到多种基体液体中制备成的系列纳米流体的导热系数，研究了纳米流体导热系数相对增加量（增加率）与固相体积含量、基体流体导热系数以及粉体种类的关系。结果表明，纳米流体导热系数增加率随固相体积含量的增加几乎呈线性增大，并随基体流体导热系数的增大而减小，在相同条件下，含碳纳米管纳米流体的导热系数增加率大于含氧化铝纳米粉体纳米流体的导热系数增加率；纳米流体导热系数增加率远比现有理论（如H＆C模型）预测值大，受各种因素的影响表现出特异性。

Study on the Thermal Conductivity of Nanofluids

Nanofluids containing alumina nanoparticles or multi-walled carbon nanotubes(MWNTs) have been prepared and their thermal conductivities have been measured using a transient hot-wire method.The relations between the thermal conductivity enhancement ratio and the volume fraction of solid phase,the thermal conductivity of base fluid,and powder species have been investigated.The results show that the prepared nanofluids,containing a small amount of alumina nanoparticles or MWNTs,have substantially higher thermal conductivities than the base fluids,with the enhancement increasing with the volume fraction of solid phase.For nanofluids containing same nanoparticles,the enhanced thermal conductivity ratio is reduced with an increase in the thermal conductivity of base fluid.No matter what kind of base fluid is used,the thermal conductivity enhancements of MWNT nanofluids are much larger than those of alumina nanofluids at same powder loading.Comparison between the experiments and the theoretical model shows that the measured thermal conductivity is much higher than the values calculated using theoretical correlation,indicating new heat transport mechanisms included in nanofluids.