Evolution of vortex modes and heat transfer in metal foam/nanoparticles composite phase change materials under the combined action of centrifugal force and magnetic field

Abstract

This study systematically investigates the heat transfer, energy storage characteristics, and vortex mode transformation mechanism of non-Newtonian nano-enhanced phase change materials (NEPCM) in metal foam. A three-dimensional numerical model based on the enthalpy-porosity method, Darcy-Forchheimer model, and local thermal non-equilibrium model was established and verified by experiments. Key parameters including nanoparticle mass fraction (${\Phi }_{wt}$), Rayleigh number (Ra), centrifugal force ($F_C$), and Magnetic number (Mn) were focused on to examine their effects on the melting heat transfer process of NEPCM. The results indicate the following: At higher Ra (10⁵), natural convection dominates heat transfer, and the effect of adding nanoparticles on enhancing heat transfer and energy storage is relatively insignificant. At Ra = 10⁴, the direction of centrifugal force achieves intervention in the evolution of the melting front as well as heat transfer and energy storage by changing the magnitude and direction of buoyancy. The coupling effects of centrifugal force and magnetic field cause the original radial flow of the fluid to deflect, resulting in the evolution from transverse vortexes to vertical vortexes. The study focuses on two typical vortex modes corresponding to centrifugal forces of - 5 g (quasi-vertical vortex) and - 1 g (fully vertical vortex) at Ra = 10⁴ and Mn = 8 × 10⁶. Finally, a vortex mode distribution diagram regulated by Ra-Mn-$F_C$ is constructed, and four vortex modes are revealed. The study aims to provide theoretical basis for the thermal management design of phase change thermal energy storage systems in aerospace environments with varying centrifugal forces.