Magnetic regulating the phase change process of Fe3O4-paraffin wax nanocomposites in a square cavity

The addition of external force provides an alternative way to promote the application of phase change materials in thermal-energy storage, space heating, and cooling systems. However, the experimental investigation using external magnetic force to regulate the phase change process is still limited. Here, magnetic Fe3O4 nanoparticles were added to paraffin wax to form phase change nanocomposites with enhanced thermal properties and controllable magnetism. The thermal properties of nanocomposites were measured and the phase change processes under magnetic controlling were experimentally and numerically investigated. A two-dimensional enthalpy-based lattice Boltzmann model with considering the external magnetic force was proposed and the measured thermal properties were used in the simulation. Good agreement between the experiment and simulation was achieved. The effects of different mass fractions of Fe3O4 nanoparticles (0, 1, 2, 3 and 4 wt%), magnetic directions, magnetic field intensities (0, 20, 40, 60 mT) on the phase change characteristics are discussed. The heat transfer efficiency in a square cavity filled with the nanocomposites developed more quickly when the paraffin wax was doped with a higher Fe3O4 mass fraction. Moreover, the phase change characteristics were controlled by the intensity and direction of the magnetic field. This study presents a method to achieve magnetically regulating phase change heat transfer characteristics that have potential applications in the energy-storage industry.