Performance improvement of thermally stratified storage tank via applying radial perforated inlet structure and dynamic flow control

Geometric optimization and fluid property control are primary approaches for improving thermal stratification efficiency in thermally stratified storage tanks (TSSTs). However, most existing studies focus on static conditions optimization, neglecting actual dynamic operational conditions. This study proposes a radial perforated inlet structure and innovatively investigates the dynamic flow control to strengthen thermal stratification. The inlet structure disperses the concentrated inlet jets into low-velocity streams, reducing the local Reynolds number while increasing Richardson and Stratification numbers, thereby suppressing turbulent mixing. This achieved 22.4 % and 12.0 % reductions in maximum and stable thermocline thickness. A phase-matching strategy between flow fluctuations and thermocline development stages was established: aligning low-flow periods with critical development stages, including initial/late formation and early stabilization stages, promotes thinner thermocline formation. Under equivalent periodic-mean flow rates, sinusoidal flow achieves 16.7 % and 26.4 % reductions in stable and maximum thermocline thickness compared to cosine modulation, and lowering stable thickness by 13.8 % compared to steady-state conditions. Adjusting flow frequency also affects thermocline development. In sinusoidal flows, reducing the frequency makes the flow closer to steady-state conditions, favoring stable upward thermocline migration. Extending the interval from 300 s to 900 s reduces stable thickness from 1.94 m to 1.81 m. For cosine flows, decreasing the interval mitigates wrinkling in the lower thermocline and accelerates upward migration while moderating thickening effects. A stable thickness reduction from 2.45 m to 2.39 m by reducing the control interval from 900 s to 300 s is achieved. These findings establish a theoretical framework for dynamic design optimization and flexible control of TSST.