Experiments on rarefied gas flows through tubes

Experiments were carried out in order to evaluate the conductance of tubes of circular cross section as a function of the Knudsen number. The range of the rarefaction level spans from the free molecular flow to the continuum regime. A different experimental approach was followed with respect to previous researches in that the mass flow rate was assigned and the corresponding pressure drop was measured. Single tubes and a bundle of capillaries were adopted. The results are compared with the existing experimental data and analytical models. An analysis of the sensitivity of the conductance to the error in measurements, in free molecular flow, was also dealt with.