Friction factor evaluation of compressible microflows using 1D Fanno flow-based numerical model

A numerical model based on the conventional Fanno flow theory for the friction factor evaluation of the gas flows inside microchannels has recently been developed by Cavazzuti et al. [1]. The current work aims to compare this numerical model with experimental results of microchannels. Pressure drop experiments are performed for a circular cross sectional microtube and a rectangular microchannel with Nitrogen gas as working fluid. The hydraulic diameters of microtube and microchannel are 100 μm and 69.4 μm respectively. Rectangular microchannel with an aspect ratio (height to width) of 0.036 is chosen for the comparison. This allows to treat the rectangular microchannel as parallel plate in the numerical Fanno model. During experiments stagnation pressure at the inlet is increased such that maximum Reynolds number is 3000 in the case of microchannel and 7600 for microtube. Results show that for the evaluation of average friction factor in both considered geometries, there exists a good match between Fanno-based 1D numerical model and experimental results in the laminar regime whereas comparison worsens as the flow approaches choking. Limitations as well as the potential reasons for the discrepancies between the developed model and experiments will be discussed.