Anomalous enhancement in thermal conductivity of nanofluid induced by solid walls in a nanochannel
Anomalous enhancement in thermal conductivity of nanofluid induced by solid walls in a nanochannel
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DOI：
10.1016/j.applthermaleng.2011.07.021
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发表时间：
2011-12
影响因子：
6.4
通讯作者：
Chengzhen Sun;Wen-qiang Lu;B. Bai;Jie Liu
中科院分区：
文献类型：
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作者：
Chengzhen Sun;Wen-qiang Lu;B. Bai;Jie Liu
采用平衡分子动力学（EMD）方法，通过Green-Kubo公式计算了Ar-Cu纳米流体在两平行壁面之间的热导率。结果表明，由于固体边界的存在，纳米颗粒在通道高度方向（z方向）的振动受到抑制，因此受限纳米流体的热导率具有明显的各向异性。垂直于z方向的热导率（λ ε）的异常增强是由于流体原子（尤其是纳米颗粒原子）与壁原子之间的强耦合作用的结果。当纳米颗粒直径为5.148 nm时，纳米流体的导热系数λ η随着纳米颗粒直径的增大而增大，从而增强了纳米流体与纳米颗粒之间的耦合。纳米颗粒体积分数对受限纳米流体导热系数的影响比宏观尺度下的影响更为明显。此外，纳米颗粒直径d = 1.370 nm的纳米流体的热导率λ max随着通道宽度的增加而减小，这是由于较长的相互作用距离导致的耦合减弱。
Thermal conductivity of Ar–Cu nanofluid confined between two parallel walls (in a nanochannel) is calculated by equilibrium-molecular-dynamics (EMD) simulation through Green-Kubo formula. The results show that the vibration of nanoparticle in the channel height direction (z-direction) is inhibited due to the presence of solid boundaries and accordingly the thermal conductivity of the confined nanofluid is obviously anisotropic. Anomalous enhancement in the thermal conductivity perpendicular to the z-direction (λ∗) appears as a result of the strong coupling interactions between the fluid atoms, especially the nanoparticle atoms, and the wall atoms. The thermal conductivity λ∗of the nanofluid confined in the channel of width h = 5.148 nm increases with the increase of the nanoparticle diameter for the strengthened couplings. The nanoparticle volume fraction effect on the thermal conductivity of the confined nanofluid is more obvious than that in macroscale. In addition, the thermal conductivity λ∗of the nanofluid with diameter of nanoparticle d = 1.370 nm decreases with the channel width increasing owing to the weakened couplings resulted by a longer interacting distance.