The flow control devices (FCD) play an important role to realize the best metallurgical performance of the tundish. An integrated workflow for designing a single-strand tundish equipped with FCD is presented in this paper. Mean age theory was applied to predict the spatial mean age distributions in the tundish. Melt change efficiency (MCE) was used as a key measure to characterize the tundish’s mixing performance. Taguchi method was employed to optimize the design factors, i.e. geometrical parameters of the FCD. The fluid flow and mixing of materials were analyzed based on the numerical simulations of a developed computational fluid dynamics (CFD) model. Compared to the residence time distribution (RTD) method, the mean age theory shows advantages in both numerical accuracy and efficiency. In addition, the size and location of undesired mixing zones can be easily identified which is essential for tundish design. The developed workflow that combined the CFD-Taguchi method and mean age theory can be used as an efficient tool for wide industrial applications.