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滑移流区域梯形微通道内气体热流逸效应及流动特性

Thermal Transpiration Effect and Flow Characteristics of Gas in Trapezoidal Microchannel in Slip Flow Region

  • 摘要: 努森压缩机是一种有效的非机械式气体升压微泵,在输送气体、压缩气体等方面具有巨大的应用潜力。基于具有滑移和跳跃边界条件的纳维-斯托克斯方程,建立适应于滑移流区域梯形微通道内气体流动二维数值模型。分析了倾角和冷热腔室温差对微通道内部气体克努森数分布、压升以及流动特性的影响规律。结果表明:微通道倾角从0°升高到5.72°,压升从129.181 Pa降低到48.291 Pa,降低了62.618%。此外,倾角越大,气体克努森数越小,但气体流速逐渐增大,泊肃叶流和热流逸流最大流速分别为0.106 m/s和0.200 m/s。当冷热腔室温差从20 K升高到100 K,努森压缩机的压升从16.081 Pa升高到92.974 Pa,提高478.161%。,温差每增加20 K,克努森数增大0.001,泊肃叶流和热流逸流最大流速分别增加约0.020 m/s和0.039 m/s。研究结果为努森压缩机复杂微通道的构建及性能优化设计提供指导。

     

    Abstract: The Knudsen compressor is an effective non-mechanical gas-boosting micropump, which has great potential for applications in transporting and compressing gases. In this paper, a two-dimensional numerical model of the gas flow inside a trapezoidal microchannel adapted to the slip flow region is established based on the Navier-Stokes equations with slip and jump boundary conditions. The effects of the inclination angle and the temperature difference between the hot and cold chambers on the Knudsen number distribution, pressure rise and flow characteristics of the gas inside the microchannel are analyzed. The results show that when the inclination angle of the microchannel increases from 0° to 5.72°, the pressure rise decreases from 129.181 Pa to 48.291 Pa, which is 62.618% lower. In addition, the larger the inclination angle is, the smaller the gas Knudsen number is, but the gas flow rate gradually increases, and the maximum flow velocities of the Poiseuille flow and the thermal transpiration flow are 0.106 m/s and 0.200 m/s, respectively. The temperature difference between the hot and cold chambers increases from 20 K to 100 K, and the pressure rise of the Knudsen compressor increases from 16.081 Pa to 92.974 Pa, which is an increase of 478.161%. For every 20 K increase in temperature difference, the Knudsen number increases by 0.001, and the maximum flow velocity of the Poiseuille flow and the thermal transpiration flow increase by about 0.020 m/s and 0.039 m/s, respectively. The results of this study provide guidance for the construction of complex microchannels in the Knudsen compressor and the optimal design of its performance.

     

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