Investigation of waterhammer in piping networks with voids containing non-condensable gas Original Research Article

A waterhammer code, PTRAN, has been developed for analyzing hydraulic pressure transients in complex piping systems and for prediction of waterhammer loads for use in design assessment of piping and associated supports. The calculation scheme uses the two-equation method of characteristics. PTRAN had been validated against a series of waterhammer experiments and theoretical calculations of sample problems. To further improve and extend the prediction capability, a void/non-condensable gas model was incorporated into PTRAN to account for the effects of air content in the voids. A set of void collapse experiments were carried out in a nominal 50 mm diameter test rig to investigate the waterhammer phenomena. The test conditions covered three sizes of initial void volumes and a selected range of air content between 0 and 100%. This paper presents the comparison of the PTRAN predictions and the experimental results for the waterhammer caused by void collapse when the void contains a known fraction of non-condensable gas. An application of the model to study the waterhammer transients for a typical high pressure emergency core cooling (ECC) system is also discussed. Considering non-condensable gas in initial voids is shown by a PTRAN simulation to be beneficial in the reduction of waterhammer loads for piping systems.