同心硅环从弹道到扩散的径向热整流
Radial thermal rectification in the concentric silicon ring from ballistic to diffusive regime
摘要：
从声子玻尔兹曼输运方程出发，研究了同心硅环从弹道到扩散的径向热整流。在弹道极限和扩散极限下，解析解证明不存在热整流。在弹道扩散区，热通量倾向于从内边界流向外边界。此外，随着特征长度（两个圆形边界之间的距离）从几十纳米增加到几十微米，热整流比增加，然后逐渐消失。这是因为随着温度梯度方向的改变，声子平均自由程也随之改变。声子平均自由程的不同最终导致热流密度或热导率的变化。随着温度的降低，最大热整流比减小。此外，对于给定的特征长度，随着内边界和外边界之间的半径比的增加，热整流比减小。
英文摘要：
The radial thermal rectification in the concentric silicon ring from ballistic to diffusive regime is investigated based on the phonon Boltzmann transport equation. In the ballistic and diffusive limits, the analytical solutions prove that there is no thermal rectification. In the ballistic-diffusive regime, the heat flux prefers to flow from the inner boundary to the outer boundary. Furthermore, as the characteristic length (the distance between two circular boundaries) increases from tens of nanometers to tens of microns, the thermal rectification ratio enhances first and then fades away gradually. It attributes to that as the direction of the temperature gradient changes, the average phonon mean free path changes. The difference of the average phonon mean free path finally leads to the change of the heat flux or thermal conductivity. As the temperature decreases, the maximum thermal rectification ratio decreases. In addition, as the radius ratio between the inner and outer boundary increases, the thermal rectification ratio decreases for a given characteristic length.
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