A new dynamic methodology for stationary and transient mass flow rate measurements

This paper reports the experimental and numerical analysis oftime-dependent rarefied gas flows through a long metallic micro-tube. The experimental methodology was conceived on the basis of the constant volume technique and adapted to measure the evolution with time ofa transient mass flow rate through a micro-tube. Furthermore, the characteristic time ofeach experiment, extracted from the pressure measu- rements in each reservoir, offered a clear indication on the dynamics ofthe transient flow as a function of its rarefaction level. Moreover we present an original methodology to extract stationary mass flow rates by using the tube conductance, which can be associated to the characteristic time of the experiment, measured for different mean pressures between two tanks. The measured conductance of the tube and the stationary mass flow rate at the inlet and outlet ofthe micro-tube was compared to numerical results obtained with the BGK linearized kinetic equation model. The results were obtained in a wide range of rarefaction conditions for nitrogen (N2).