Experimental and theoretical investigation of waterhammer induced by steam-water countercurrent flow a long horizontal pipe

Abstract

The condensation-induced waterhammer in a horizontal pipe is the most damaging form of waterhammer and its diagnosis is extremely difficult because of the complex nature of the underlying phenomena that occur at the steam-water interface. The current modeling concepts do not predict well the lower and upper boundaries of the waterhammer accident occurred at San Onofre nuclear power station. In the present work, improved models that can predict the lower and upper boundaries of the initiation of waterhammer induced by steam-water countercurrent flow in a long horizontal pipe is derived. In the analysis the interfacial friction factor, the criterion of onset of waterhammer, and the interfacial heat transfer coefficient are the major constitutive relations, but there are several limited ranges in the application of current correlations being used. Several experiments have been conducted in adiabatic counter-current stratified flow with round pipe and rectangular duct test sections to develop the interfacial friction factor, the criterion of initiation of waterhammer, and the correlation of water depth. First, an adiabatic semi-empirical correlation for interfacial friction factor has been developed based on the surface roughness concept. A comparison of the measured data including others with the predictions of the present correlation shows that the agreement is within ±30%error and that the present correlation covers a broader range of water flow rate than the previous correlations. Second, a theory which can calculate the wave height and the criterion of onset of slug flow in a stratified wavy flow regime has been developed based on the total energy concept. This theoretical criterion agrees better with the measured data than the other criteria available in the literature, but predicts about 92~107%. An empirical formulus for the criterion has been also developed and compared with others. Third, correlations which can predict the slope of liquid surface and ...