Numerical study on flow pattern of sonic steam jet condensed into subcooled water

For stable sonic steam jet, conical and ellipsoidal steam plumes were observed by many researchers. Restricted by experimental method, the difference in flow and heat transfer characteristic between conical and ellipsoidal steam plumes was still unclear. To reveal the difference between the two kinds of steam plumes, three-dimensional steady numerical simulations were carried out with Eulerian multiphase model, and a thermal equilibrium phase change model was inserted into Fluent as a user defined function (UDF) to investigate the condensation phenomenon. The CFD results were compared with experimental results to testify the correctness of simulation, and good agreement was observed. Then steam pressure was varied to study its effect on the process of condensation jet. Conical and ellipsoidal steam plumes were obtained under different operating conditions. For conical steam plume, it is compressed near nozzle exit along radial direction, and the pressure in steam plume is larger than ambient pressure. However, when it comes to ellipsoidal steam plume, it expands near the nozzle exit along radial direction, when steam plume expands to the maximum extend, the pressure in steam plume is reaching the bottom, almost the same as ambient pressure. Besides, the influence of flow characteristic of steam in plume on axial temperature and steam plume shape was analyzed. When steam in plume reaches supersonic, the shape of steam plume shows ellipsoidal shape, and there is a peak along axial temperature distribution. Otherwise, it presents conical shape and axial temperature decays to ambient water temperature monotonously.