Transition Flow through Short Circular Tubes

The mass flow of nitrogen gas through short circular tubes was measured in the transition flow regime with the length-to-diameter ratios varied between 0.005 and 1 and with pressure ratios across the tubes varied between 1 and 20. The range of Knudsen numbers (ratio of upstream mean free path to the diameter of the tube) covered was between 0.1 to 1.7. Comparisons are made of the measurements with existing theories, and a semiempirical equation is developed to correlate the measured data at all of the pressure ratios, Knudsen numbers, and length-to-diameter ratios covered in the present study.