Magnetic-regulated flow instability and heat transfer characteristics of composite phase change materials under centrifugal force in microgravity condition

This study establishes a three-dimensional numerical model to systematically investigate the heat transfer characteristics and flow instability mechanisms of nano-enhanced phase change material (NEPCM) driven by thermocapillary convection under the coupled effects of magnetic field and centrifugal field in microgravity. The thermocapillary effect, magnetic field, and centrifugal buoyancy are characterized by the shear stress boundary condition, Kelvin force source term, and centrifugal buoyancy source term, respectively. The influences of the Marangoni number (Ma), centrifugal buoyancy number (Ce), and magnetic number (Mn) are systematically examined. The results show that centrifugal force regulates melting kinetics through synergistic or competitive interactions with thermocapillary convection, and its effect exhibits significant directional dependence. Centrifugal buoyancy in the Y -direction (parallel to the heating direction) and Z -direction (perpendicular to the heating direction) significantly improves thermal storage efficiency. At Ma = 5 × 10³, Ce_Y = 5 × 10⁴ and Ce_Z = −5 × 10⁴ lead to 57% and 55% increases in thermal storage efficiency compared with the case without centrifugal force, respectively. The coupling of Kelvin force and centrifugal buoyancy induces vertical vortices and local oscillatory convection, which reconstructs the heat transfer path. The regulated flow is classified into three modes: stable, transitional, and local periodic oscillation. A convection pattern map in the Ma−Mn−Ce parameter space is constructed. It is found that the coupling of strong magnetic field and centrifugal force at high Mn tends to induce instability, and Y -direction centrifugal force is more likely to excite flow field disorder. This study provides a theoretical basis for the optimal design of space thermal control and energy storage systems in microgravity environments.