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热流逸效应可输送气体并产生压力差,可利用其抽真空。本文建立了描述热流逸效应及其抽真空泵送特性的数学模型,以空气为例探讨了气体流态(努森数)、微通道特征尺寸和径长比以及温差等参数对压力比、净质量流量、抽速和无量纲抽气时间的影响。结果表明,压力比、净质量流量、抽速和无量纲抽气时间均随温差的增大而增大,但过大的温差对提高流量不明显且使抽真空达到稳态过程变得相对缓慢,应根据实际条件确定适宜温差。净质量流量和抽速随努森数增大而减小,且在过渡流区域还受径长比的影响;压力比和无量纲抽气时间在过渡流区域随努森数增大而增大,但在自由分子流区域与努森数无关;故应根据实际需求权衡净质量流量与压力比以确定适宜的热流逸发生条件、并控制气体流态来调整抽气特性。
The thermal runaway effect can deliver gas and create a pressure differential that can be used to evacuate. In this paper, a mathematical model describing the thermal runaway effect and its pumping characteristics was established. Taking the air as an example, the effects of gas flow regimes (Knudsen number), microchannel feature size and radius-length ratio, and temperature difference on pressure ratio, net mass Flow, pumping speed and dimensionless pumping time. The results show that the pressure ratio, net mass flow rate, pumping speed and dimensionless pumping time increase with the increase of temperature difference, but too large temperature difference is not obvious to increase the flow rate and make the vacuum to reach the steady state process relatively slowly , Should be based on the actual conditions to determine the appropriate temperature. The net mass flow rate and pumping speed decrease with the increase of Knudsen number, and are also affected by the ratio of diameter to length in the transitional flow region. The pressure ratio and the dimensionless pumping time increase with the increase of Knudsen number in the transition flow region , But has nothing to do with the Knudsen number in the area of free molecular flow; therefore, the net mass flow to pressure ratio should be weighed against the actual demand to determine the appropriate conditions for heat flow to escape and to control the gas flow to adjust the pumping characteristics.