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

A waterhammer code, PTRAN, has been developed for analyzing hydraulic press ure transients in complex piping systems and for prediction of waterhammer loads for use in design assessment of piping and associated supports. The c alculation scheme uses the two-equation method of characteristics. PTRAN ha d been validated against a series of waterhammer experiments and theoretica l calculations of sample problems. To further improve and extend the predic tion capability, a void/non-condensable gas model was incorporated into PTR AN to account for the effects of air content in the voids. A set of void co llapse experiments were carried out in a nominal 50 mm diameter test rig to investigate the waterhammer phenomena. The test conditions covered three s izes 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 t he experimental results for the waterhammer caused by void collapse when th e void contains a known fraction of non-condensable gas. An application of the model to study the waterhammer transients for a typical high pressure e mergency core cooling (ECC) system is also discussed. Considering non-conde nsable gas in initial voids is shown by a PTRAN simulation to be beneficial in the reduction of waterhammer loads for piping systems. (C) 2000 Publish ed by Elsevier Science S.A. All rights reserved.