Oscillation characteristics of periodic condensation induced water hammer with steam discharged through a horizontal pipe

•Condensation induced water hammer (CIWH) regime maps under different pipe lengths were obtained.•Transition criterion of periodic CIWH considering pipe length was developed.•Frequency correlation of periodic CIWH considering pipe length was developed.•Correlation of the occurrence position of periodic CIWH was developed. Condensation induced water hammer (hereafter, CIWH) phenomenon is widely observed in various industrial operations, causing severe damage to related equipment and personal safety. This study investigated the CIWH regime map and the oscillation characteristics of periodic CIWH under different pipe lengths when the steam was discharged into a water tank through a horizontal pipe. First, the CIWH regime maps were obtained under different pipe lengths, with distinct regimes of periodic CIWH and non-periodic CIWH. A criterion was proposed to predict the transitions from periodic to non-periodic CIWH. It was found that the occurrence frequency of periodic CIWH decreased with the increase in the pipe length. An empirical correlation of Strouhal number, non-dimensionalized occurrence frequency, was developed to predict the occurrence frequency. The correlation could reproduce more than 95 % of the experimental data with the error of -20.2 % to 23.7 %. The pressure oscillation intensity of periodic CIWH was analyzed. The oscillation intensity increased when the pipe length and steam mass flux increased, whereas it increased first and then decreased when pool temperature increased. Finally, the occurrence position of periodic CIWH was found to be nearly constant under the same test condition. The position moved downstream of the steam when the pipe length and Froude number increased, and Jakob number decreased. The average occurrence position was correlated with the error of -17.1 % to 18.4 %.