Experimental study on flow characteristics of gas transport in micro- and nanoscale pores

Weijun Shen,Xiao Hu,Genmin Zhu,Fuquan Song,Weiyao Zhu

doi:10.1038/s41598-019-46430-2

Abstract

Gas flow behavior in porous media with micro- and nanoscale pores has always been attracted great attention. Gas transport mechanism in such pores is a complex problem, which includes continuous flow, slip flow and transition flow. In this study, the microtubes of quartz microcapillary and nanopores alumina membrane were used, and the gas flow measurements through the microtubes and nanopores with the diameters ranging from 6.42 μm to 12.5 nm were conducted. The experimental results show that the gas flow characteristics are in rough agreement with the Hagen-Poiseuille (H-P) equation in microscale. However, the flux of gas flow through the nanopores is larger than the H-P equation by more than an order of magnitude, and thus the H-P equation considerably underestimates gas flux. The Knudsen diffusion and slip flow coexist in the nanoscale pores and their contributions to the gas flux increase as the diameter decreases. The slip flow increases with the decrease in diameter, and the slip length decreases with the increase in driving pressure. Furthermore, the experimental gas flow resistance is less than the theoretical value in the nanopores and the flow resistance decreases along with the decrease in diameter, which explains the phenomenon of flux increase and the occurrence of a considerable slip length in nanoscale. These results can provide insights into a better understanding of gas flow in micro- and nanoscale pores and enable us to exactly predict and actively control gas slip.

Highlights

Fluid flow behavior in the micro- and nanoscale channels and pores is crucial for the development of microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS)[1] and for studies on cells and nanofilms[2], shale gas resources[3]
In the micro- and nanoscale channels and pores fluid flow is in a laminar flow state[38,39] and the Hagen-Poiseuille (H-P) equation can be used to describe the theoretical gas flux
Where Qhp is the theoretical gas flux; D is the diameter of the nanopores and microtubes; p is the pressure; M is the gas molar mass; μg is the gas viscosity; Z is the gas deviation factor; R is the universal gas constant; T is the temperature; dp/dl is the pressure gradient; and l is the length of the pore

Summary

Introduction

Fluid flow behavior in the micro- and nanoscale channels and pores is crucial for the development of microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS)[1] and for studies on cells and nanofilms[2], shale gas resources[3]. There is a good possibility to understand multiple gas transport mechanisms in the micro- and nanoscale channels and pores using the alumina membrane. The microtubes of quartz microcapillary and the nanopores of alumina membrane were used, and the gas flow measurements through the microtubes and nanopores with the diameters range of 6.42 μm to 12.5 nm were conducted to study gas flow characteristics. The flow resistance was calculated to explain the increase in flux and the occurrence of an enormous slip length in nanoscale These results can provide a better understanding of gas flow characteristics in the micro- and nanoscale channels and pores. The microtubes of quartz microcapillary and nanopores alumina membrane were used to study fluid flow behavior in the micro- and nanoscale channels and pores. The detailed measurement of the nanopores are shown in the Supplementary Material (Section S-I)

Methods

Results

Conclusion