Uncertainty Analysis of Leak Rate Calculation through Pipes and Slits

Abstract

Results of a numerical investigation of the two-phase critical flows of initially subcooled or saturated water through pipes and slits are reported. The study of such flows is relevant to the prediction of leak rates through cracks or breaks in high energy piping systems. Calculation results are compared to the reported experimental data. Effects of flow parameters such as the subcooling temperature, stagnation pressure, flashing inception and friction on the critical mass flow rate are stressed. Results showed that a reasonably good agreement between the predicted values and the measured data was found in pipe flows, but the model underpredicts the experimental data for the artificial slits for higher subcooling temperature in most cases. The agreement was improved when the location of the flashing inception was set at the actual location provided by the experiment. It was also found that the influence of the friction coefficients on the critical mass flux was significant and thus appropriate choice or estimation of the friction factor correlation and the surface roughness would be of great importance for the accurate prediction of two-phase critical flows.