Parametric study of magnetic-field-induced nanoparticle aggregation on PCM heat transfer performance

To unveil the heat transfer characteristics of composite PCM under uniform magnetic field regulation, this study investigates the actual properties of nanoparticle aggregation under various parameter conditions and numerically examines their impact on the melting process of PCM. The total enthalpy-based lattice Boltzmann method, validated through two aspects, is implemented. The deviation of melt-front location and equivalent thermal resistance of PCM region are assessed as evaluation criteria. Results show that, under uniform magnetic field, magnetic nanoparticles aggregate into bundle structures aligned with the direction of magnetic induction line. While the formed heat conduction network enables efficient heat diffusion, the distribution properties of nanoparticle aggregation are dominated by parameters such as mixing ratio and tilt angle. At a mixing ratio of 0.5, the average deviation of melt-front location can be maintained below 2 × 10 -5 m, indicating uniform melting process. At higher mixing ratios, nanoparticles tend to aggregate into larger size and sparsely distributed bundle structure. While this reduces the uniformity of the melting process, it is more conductive to reduce average thermal resistance. Adjusting the tilt angle between the direction of magnetic induction line and the boundary heat flux allows for regulation of the melting process by altering the arrangement of the aggregated structures. Ultimately, the average thermal resistance in the PCM region can regulated between 0.3 × 10 -3 and 2.1 × 10 -3 m 2 ·K/W. According to the orthogonal design, the mixing ratio and tilt angle yield the most substantial impacts on melting uniformity and average equivalent thermal resistance, respectively.