Numerical investigation of condensation-induced water hammer effects in horizontal and vertical cold reheat pipes

Condensation-induced water hammer (CIWH) is an unavoidable phenomenon in power generation facilities and must be properly adjusted for the thermal efficiency and safety of the system. This study simulated CIWH in a realistic steam pipe to analyze its characteristics in horizontal and vertical pipe sections. Additionally, CIWH intensities with respect to key parameter changes were explored for its mitigation. Numerical simulations for the CIWH were performed using an OpenFOAM solver, ICFMCondFOAM, which was validated for multiple phase change computational fluid dynamics (CFD) problems. The geometric and operating conditions of the cold reheat pipe of our partner company were used for CFD simulations. To assess the intensity of the water hammer effect, various inlet water flow rates and steam temperatures were employed and pressure over time was recorded at two measurement points: horizontal and vertical sections. Results of the CFD simulation show that the CIWH phenomenon behaves differently in horizontal and vertical pipes. CIWH strength was also evaluated using the Froude (Fr) and modified Jakob (Ja) numbers. Smaller Fr and larger Ja were found to be desirable for lowering the pressure increase ratios caused by the CIWH in both the horizontal and vertical pipe sections.