Analysis of swarm flow and bubble residence time under pool scrubbing conditions

In severe accidents of nuclear power plants, large amounts of fission products existing as radioactive aerosols are released. Pool scrubbing plays an important role in the removal of radioactive aerosols. Bubble residence time is one of the key parameters to determine the efficiency of aerosol removal, especially in the swarm flow region which makes a very important contribution to the total aerosol removal. In this study, the Euler-Euler-Lagrangian approach is built to track the evolution of bubble motion and to determine the bubble residence time in the liquid pool. Specifically, the Euler-Euler two-fluid approach is utilized to resolve the flow field of gas and liquid phases, while the Lagrangian approach is employed to track the discrete bubbles and to obtain the bubble residence time. The results reveal that the present approach is feasible to predict the bubble dynamics and residence time in the liquid pool. Bubble residence time is dependent on the initial position, where bubbles deviating from the central region could remain inside the liquid pool for a longer physical time. The bubble diameter, volume flow rate and submergence height are key parameters affecting the bubble residence time. And comparison between the simulated bubble residence time and the model-predicted results is carried out, indicating the discrepancy of simulated residence time and limitations of the existing model at high volume flow rate and high submergence.