Karakitsiou S, Holst B, Hoffmann A C
Department of Physics and Technology, University of Bergen, Allegaten 55, 5007 Bergen, Norway.
Rev Sci Instrum. 2016 Dec;87(12):125104. doi: 10.1063/1.4963695.
The pressure-driven gas flow through micro- and nano-porous structures is particularly interesting for innovative technologies such as microelectromechanical and nano-mechanical-electrical systems. The classical continuum assumption breaks down for rarefied flow through channels with a characteristic dimension comparable to the mean free path of the gas. Theories based on molecular interactions have been formulated to predict the flow at high Knudsen numbers. Measuring rarefied gas flow experimentally is a challenge since only a few studies have been able to determine flowrates in the molecular flow regime. Here we present the design of an experimental apparatus, which can be used to measure the flow of gases through nano- and microscale channels in the flow regimes where molecular effects are critical. The equations used to design the apparatus are given, focusing on the slip and transition flow regimes (together sometimes called "Intermediate flow regime"). A channel with a diameter of 325 μm ± 5μm and a length of 2 mm was tested experimentally with the apparatus for a wide range of Knudsen numbers (10 < Kn < 1 × 10) demonstrating its suitability through the slip and transition regime (2.23 × 10 < Kn < 2.26).
对于微机电系统和纳米机电系统等创新技术而言，压力驱动的气体流经微孔和纳米孔结构的情况尤其引人关注。对于通过特征尺寸与气体平均自由程相当的通道的稀薄流动，经典的连续介质假设不再适用。基于分子相互作用的理论已被提出，用于预测高克努森数下的流动。通过实验测量稀薄气体流动是一项挑战，因为只有少数研究能够确定分子流态下的流量。在此，我们展示了一种实验装置的设计，该装置可用于在分子效应至关重要的流动状态下测量气体通过纳米级和微米级通道的流动。给出了用于设计该装置的方程，重点关注滑移流和过渡流态（有时一起称为“中间流态”）。使用该装置对一个直径为325μm±5μm、长度为2mm的通道进行了实验测试，该通道在很宽的克努森数范围（10＜Kn＜1×10）内进行测试，结果表明其适用于滑移和过渡流态（2.23×10＜Kn＜2.26）。
