Abstract The optimization of thermal performance in star-shaped thermal energy storage (TES) units filled with nano-enhanced phase change materials (NEPCMs) is investigated in this study. Several geometric configurations of the irregular enclosure are considered by varying the undulation number. An inner rotating cylinder is placed within the domain, and unlike previous studies, a wide range of clockwise angular velocities is examined. Four operating cases are analyzed based on the heating mode and cylinder motion: (i) internal heating with rotation, (ii) internal heating with a stationary cylinder, (iii) external heating with rotation, and (iv) external heating with a stationary cylinder. The flow region is filled with a dual-energy permeable medium, where the host fluid is modeled as a red blood cell (RBC)-based suspension. To solve the governing equations within the irregular geometry, the control volume method is supported by a point-in-polygon determination test. Expressions for the total heat transfer rate are derived, and the Nusselt numbers of both the fluid and solid phases are optimized using the Response Surface Methodology (RSM). The major results indicate that at higher Rayleigh numbers, buoyancy dominates over rotation-induced circulation. Additionally, stronger rotation promotes mixing and reduces thermal stratification. Furthermore, in the case of external heating, the presence of internal clockwise rotation enhances flow activity by 44.7 % compared to a stationary cylinder. The novelty of this work appears in presenting an innovative numerical investigation of micropolar NEPCM flow in an irregular star-shaped porous TESS under LTNE conditions, providing new quantitative insights for optimizing advanced thermal energy storage designs.
Ahmed et al. (Thu,) studied this question.