Numerical study on oscillation characteristics of large chugging of direct condensation of steam in a Tee junction with flowing sub-cooled water

Abstract

Direct contact condensation (DCC) of steam has the advantage of high efficiency of heat and mass transfer, and thus it is widely used in many industry fields, including steam ejectors, heat exchangers and safety systems of nuclear power plant. However, this process may cause damage to the relevant equipment because of temperature and pressure oscillations, particularly when condensation regime is large chugging. In this study, numerical simulation as well as verification experiment was performed for large chugging of direct contact condensation in a Tee junction with flowing sub-cooled water. Six stages of large chugging in a cycle were found based on the volume fractions of steam and water. In addition, sub-cooled water streamlines changed directions at each different stage. Temperature oscillation was found at the inner wall of the vertical branch pipe, and the range of influence of thermal cycling was from the middle to the exit for the vertical branch pipe. There existed pressure oscillation at the inner wall of the horizontal main pipe below the vertical branch pipe exit, furthermore, negative pressure and positive pressure regions were found in the process of steam bubble expanding and contracting, respectively.