Experimental and theoretical analysis on characteristics of gas leakage through capillary tubes

Abstract

To analyze aerosol leakage in containment cracks after severe accidents, the experimental facility for the analysis of the characteristics of gas leakage in capillary tubes was built to investigate eight kinds of capillary tubes with different inner diameters under different pressure differences. Moreover, the applicability of the classical Hagen-Poiseuille formula was analyzed and evaluated based on the comparison between the experimental data and theoretical model results. Results show that the formula can accurately predict the gas leakage rate when the flow state in the capillaries is incompressible laminar flow. However, under the condition of a large pressure difference between the two ends of the capillaries, the flow pattern in the capillaries will change from laminar flow to turbulent flow, and the average Mach number will change from the growth region to the smooth region, showing choking characteristics. Even in the capillaries with small inner diameters, the transition of the Mach number can occur in the laminar region. As a result, the compressibility of fluid in the capillaries becomes significant, which influences the prediction accuracy of the theoretical formula.