Numerical Simulations on Dynamic Behavior of Multiphase Flow and Heat Transfer in a Round Mold with a Swirling Flow Tundish Design

Three-dimensional computational fluid dynamics simulations were carried out to investigate the multiphase flow and heat transfer in a round mold, when using swirling flow generator (SFG) designs in a tundish. The results show that an impinging flow in the mold is significantly suppressed by using a SFG design, compared to when using a conventional tundish. This is due to the rotational flow momentum, which forces the steel to move toward the mold wall. When using SFG designs, the whole flow field shows periodic characteristics in transient simulations. At a given casting speed, the velocity fluctuation period and fluctuation range in the submerged entry nozzle depend on the SFG inlet area as well as the inlet velocity. As the inlet velocity increases from 0.185 to 0.37 m/s (inlet area decreases from 0.0048 to 0.0024 m(2)), the velocity fluctuation period decreases from 3 to 2 seconds and the fluctuation range increases from +/- 10.5 to +/- 18.2 pct. However, a symmetrical distribution of the flow field is obtained in the time-averaged results of 9 and 6 seconds intervals for SFG inlet velocities of 0.185 and 0.37 m/s, respectively. In addition, within one velocity fluctuation period, the time-averaged temperature field generally has a uniform distribution. As the SFG inlet velocity increases from 0.185 to 0.37 m/s, the steel super-heat further decreases in the mold and the temperature is increased by around 2 K near the meniscus. Finally, in the current mold with a diameter of only 150 mm, the removal ratio of inclusions to the mold top surface is low by using both SFG designs. The removal ratio of 10 mu m spherical inclusions is 10 pct lower compared to when using a conventional tundish.