Yu W, Choi S U S
Argonne National Laboratory, Energy Technology Division, 9700 S. Cass Avenue, Building 335, Argonne, Illinois 60439, USA.
J Nanosci Nanotechnol. 2005 Apr;5(4):580-6. doi: 10.1166/jnn.2005.065.
The theoretical investigation of the effective thermal conductivities of nanofluids, a new class of solid-liquid suspensions, is important in both predicting and designing nanofluids with effective thermal conductivities. We have developed a new thermal conductivity model for nanofluids that is based on the assumption that monosized spherical particles are uniformly dispersed in the liquid and are located at the vertexes of a simple cubic lattice, with each particle surrounded by a liquid layer having a thermal conductivity that differs from that of the bulk liquid. This model nanofluid with a cubical arrangement of nanoparticles gives a more practical upper limit of thermal conduction than a model nanofluid with a parallel arrangement of nanoparticles. The new model unexpectedly shows a nonlinear relationship of thermal conductivity with particle concentration, whereas the conductivity-concentration curve changes from convex upward to concave upward with increasing volume concentration. The effects of particle and layer parameters on the effective thermal conductivities are also analyzed. A comparison of predicted thermal conductivity values and experimental data shows that the predicted values are much higher than the experimental data, a finding that indicates that there is a potential to further improve the effective thermal conductivities of nanofluids with more uniformly dispersed particles.
纳米流体作为一类新型的固液悬浮液，对其有效热导率进行理论研究对于预测和设计具有有效热导率的纳米流体而言至关重要。我们基于单尺寸球形颗粒均匀分散在液体中且位于简单立方晶格顶点的假设，开发了一种新的纳米流体热导率模型，每个颗粒被一层热导率不同于本体液体的液层包围。这种具有纳米颗粒立方排列的模型纳米流体比具有纳米颗粒平行排列的模型纳米流体给出了更实际的热传导上限。新模型意外地显示出热导率与颗粒浓度之间的非线性关系，而电导率 - 浓度曲线随着体积浓度的增加从向上凸变为向上凹。还分析了颗粒和液层参数对有效热导率的影响。预测热导率值与实验数据的比较表明，预测值远高于实验数据，这一发现表明通过使颗粒更均匀地分散，有可能进一步提高纳米流体的有效热导率。
