Research on Thermal Stratification Characteristic in Thermally Stratified Storage Tank: Optimization of Radial Perforated Inlet Structure and Dynamic Flow Control

Abstract

Geometric optimization and fluid property control are primary approaches for enhancing thermal stratification efficiency in thermally stratified storage tanks (TSST). However, existing studies mostly 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 designed inlet structure disperses the concentrated inlet jets into low-velocity streams, the local Reynolds number is reduced while increasing Richardson and Stratification numbers, 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, sine-modulated flow achieves 16.7% and 26.4% reductions in stable and maximum thermocline thickness compared to cosine modulation, while lowering stable thickness by 13.8% compared to steady-state conditions. Flow adjustment frequency analysis reveals that extended intervals approximate steady-state conditions, favoring stable upward thermocline migration in sine-modulated flows. Changing the adjustment interval from 300 s to 900 s can achieve a thickness reduction of 1.94 m to 1.81 m. Conversely, shortened intervals with reduced amplitudes mitigate lower thermocline wrinkling disturbances in cosine-modulated flows, accelerating upward movement while moderating thickening effects. Achieved stable thickness reduction from 2.45 m to 2.39 m by reducing the control interval from 900s to 300s. These findings establish a theoretical framework for dynamic design optimization and flexible control of TSST.

Keywords: Thermally stratified storage tank, Inlet structure optimization, Dynamic flow control, Thermocline thickness, Thermal stratification efficiency