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中国物理学会期刊

非对称纳米通道内界面热阻的分子动力学研究

CSTR: 32037.14.aps.69.20200491

Molecular dynamics study of interface thermal resistance in asymmetric nanochannel

CSTR: 32037.14.aps.69.20200491
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  • 微尺度系统传热具有较小的热惯性和较快的热响应, 在控制传热方面具有独到的优势. 本文利用分子动力学方法研究了纳米通道中壁面温度及壁面润湿性不同时, 静态流体和动态流体下界面热阻的变化规律. 结果表明, 在静态流体中, 壁面润湿性的增强会显著降低界面热阻, 对于温度不同的壁面, 当润湿性较弱时, 可以观察到高温壁面处的界面热阻高于低温壁面处, 反之, 当润湿性较强时, 壁面温度对界面热阻的影响较小; 对流体区域施加外力使流体流动, 结果显示外力的增加能有效提高系统的热通量, 流体温度升高. 当润湿性较弱时, 外力的增大能显著减低界面热阻, 而随着壁面润湿性增强, 外力对界面热阻的影响逐渐减小. 此外, 本文将界面热阻与壁面吸附流体分子数量相联系, 发现在静态流体中, 界面热阻值与壁面吸附流体分子的数量呈负相关; 而在动态流体中, 外力的变化对吸附分子数量的影响较小, 壁面润湿性的强弱是影响壁面吸附流体分子的主要影响因素.

     

    Heat transfer in a micro-scale system has less thermal inertia and faster thermal response, which has unique advantages in controlling heat transfer. Interface thermal resistance is an important physical quantity that reflects the heat transfer performance of the interface on a micro-scale. In this paper, the interface thermal resistance os static fluid and flowing fluid in nanochannel, which are different in the wall temperature and wettability, are studied by the molecular dynamics method. In the static fluid, the results show that the wall wettability has a significant influence on the interface thermal resistance, and the stronger the wall wettability, the smaller the values of interface thermal resistance is. For the walls with different temperatures, it can be observed that the interface thermal resistance on high temperature wall is higher than that on low temperature, when the wall wettability is weaker. On the contrary, when the wall wettability is stronger, the effect of wall temperatures on the interface thermal resistance is negligible. An external force applied to the fluid domain makes the fluid flow. In the flowing fluid, the results show that the variation of wall wettability and external force can lead to the slip to different degrees at the interface, and the slip-induced frictional viscous heat is generated at the solid-liquid interface, and thus increasing the fluid temperature and the heat flux of the system. The effect of external force on the thermal resistance is limited by the wall wettability. When the wall wettability is weaker, the increase of the external force will make the interface slip more easily and the thermal resistance decrease. With the stronger wall wettability, it is difficult to make the interface slip obviously with the increase of external force, and the influence of external force on interface thermal resistance decreases. The heat transfer performance at the solid-liquid interface is related to the number of fluid molecules adsorbed on the wall surface. The results show that in the static fluid, the increase of wall wettability will make more fluid molecules adsorbed on the wall, and the arrangement becomes more and more regular, which causes the interface thermal resistance to decrease and is beneficial to the interface heat transfer. In the flowing fluid, the change of external force has less influence on the number of adsorbed molecules, and the wall wettability is the main factor affecting the adsorption of fluid molecules on the wall.

     

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