New concept to measure the Poiseuille coefficient of rarefied gas flow driven by a large pressure drop

The Poiseuille coefficient, which relates the mass flow rate through a long capillary to the local pressure gradient, is an important characteristic in designing various technological processes that include vacuum systems as part. This quantity is usually calculated by solving numerically the linearized Boltzmann equation assuming a small pressure gradient and, therefore, the mass flow rate is small too. As a result, to extract accurately this coefficient from experimental measurements, the mass flow rate must remain small. The present paper proposes a novel approach to extract the Poiseuille coefficient from a measurement of mass flow rate driven by a large pressure drop. Under these conditions, the flow rate increases significantly and, hence, the experimental error is reduced. The proposed method will help experimentalists in designing measurement devices to determine the Poiseuille coefficient with a higher accuracy.