Magnetohydrodynamic mixed convection of micropolar nanoencapsulated phase change materials in a channel–cavity system for enhanced thermal energy storage

This study numerically investigates magnetohydrodynamic mixed convection of a micropolar nanoencapsulated phase change material (NEPCM) suspension in a channel–cavity system representative of compact latent heat thermal energy storage units. The configuration includes an embedded cylindrical obstruction to regulate flow structure and thermal transport characteristics. A steady-state finite element framework is employed to solve the coupled momentum, microrotation, energy, and concentration equations under the combined influence of buoyancy forces, magnetic field, and thermal radiation. The objective is to evaluate the interacting roles of internal particle rotation, latent heat storage, and Lorentz force on double-diffusive transport within a confined geometry. In contrast to conventional Newtonian nanofluid models, the present formulation simultaneously incorporates micropolar dynamics and phase change behavior, enabling a more realistic representation of advanced thermal storage suspensions. The results show that a balanced convection regime ( R i varied from 0 to 2) yields the most favorable thermo-hydrodynamic performance near R i ≈ 1 , where the average Nusselt number increases by 9.49% compared to R i = 0 due to constructive coupling between forced and natural convection, whereas further buoyancy enhancement to R i = 2 deteriorates transport efficiency. Thermal radiation, when increased from R d = 1 to R d = 5 , enhances the average Nusselt number by 76.52% while reducing the pressure difference by 6.86%, intensifying internal heat diffusion while moderating pressure penalties. Increasing the micropolar parameter from Γ = 0 . 1 to Γ = 2 enhances heat transfer by 14.33% but raises drag by 34.19%, indicating a heat transfer-hydrodynamic trade-off. Additionally, aiding solutal buoyancy strengthens mass transfer, particularly at higher Lewis numbers. The coordinated adjustment of micropolar coupling, buoyancy ratio, radiation parameter, and geometric configuration is shown to enhance the effectiveness of NEPCM-based thermal energy storage systems within the investigated parameter ranges. • Optimal thermal storage performance occurs at Richardson number Ri ≈ 1. • Radiation enhances heat transfer by 76.5% while reducing pressure drop by 6.9%. • Micropolar effects boost heat transfer 14.3% but increase drag by 34.2%. • Magnetic field suppresses convection by 30%, offering a flow control mechanism. • Aiding solutal buoyancy critically optimizes phase change in NEPCM suspensions.