A review of rarefied gas flow in irregular micro/nanochannels

Abstract

In today’s complex micro–electro–mechanical systems (MEMS), investigation of flow through irregular micro/nanochannels, such as bended channels, variable cross-sectional area channels, and those with rough surfaces, can contribute considerably to efficient designing of the microdevices and to gain a better understanding of the flow structure in these geometries. The present paper reviews the prominent studies published in literature on rarefied gas flow through these types of complex geometries. The main focus of the study is to explore the physical aspects of the findings and the analyses provided in support of the results. Finally, the areas in which a gap exists in literature and could be subjects of future studies are introduced.

A Review of the Complex Flow and Heat Transfer Characteristics in Microchannels

“…The degree of rarefaction is usually distinguished by the Knudsen number ( Kn ), which is defined as the ratio between the mean free path of molecules and the characteristic length scale [ 53 ]. …”

“…The above two formulas take into account the discontinuous effects caused by rarefaction, and most existing studies on microchannel heat transfer have successfully used these equations. The degree of rarefaction is usually distinguished by the Knudsen number (Kn), which is defined as the ratio between the mean free path of molecules and the characteristic length scale [53].…”