Pressure-driven gas flow

The last category is the pressure-driven gas flows, which are typical in micro gas fluidic and micro heat transfer systems. Because the channel diameter or width in micro gas fluidic systems is in the scale of sub-micrometer or less, ultra-thin gas lubrication theory plays an important role in... 

A pressure-driven gas flow is generated by applying a pressure difference between the inlet and the outlet of a fluidic system, for example, a channel. Due to very small hydraulic diameters, pressure-driven gas flows in microchannels are laminar. Gas microflows are distinct from gas macroflows by rarefaction effects which appear as soon as the mean free path of the molecules is no longer negligible compared with the hydraulic diameter of the microchannel. For such rarefied flows, the classic Poiseuille model is no longer valid, and other models should be used, according to the rarefaction level, which is quantified by the Knudsen number. 

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