The paper presents the design and analysis of differential pressure micro-flowmeter, for low flows of gases (0.1–120 mg/s) with different inlet pressure conditions (1–4 bars). The device consists of a planar micro orifice obstruction in a rectangular microchannel, with two pressure ports, upstream and downstream of the constriction. The particularities of this micro orifice is the small scale and the planar two-dimensional configuration, i.e. only in the width of the rectangular microchannel changes. A series of micro orifice sizes will be studied, with hydraulic diameters ranging from 200 to 465 μm and channel Reynolds numbers up to 7000. The geometric parameters of these micro orifices were determined to have a measurable pressure drop and to avoid choking. The calculation of the pressure drop through a micro orifice are represented using analytical equations, and modeled numerically using computational fluid dynamics to further investigate the flow patterns and 3D effects. The discharge coefficient is determined for each orifice micro-flowmeter by numerical analysis. This work aims to implement integrated mass flow measurements in micro chemical and fluidic devices that cannot use macroscopic mass flow meters, either due to their large volume, high cost, or inability to withstand harsh environments.

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