Experimental investigation of the effect of rotating magnetic field on the melting performance enhancement of paraffin/nano-Fe₃O₄ composite phase change material

The widespread application of latent heat thermal storage technology is significantly hindered by the slow heat transfer rate resulting from the low thermal conductivity of phase change materials (PCMs). In this study, a novel approach is proposed to enhance the charging performance. It involves incorporating magnetic nanoparticles (Fe3O4) with high thermal conductivity into PCMs (paraffin) and utilizing a rotating magnetic field to intensify convective heat transfer within the magnetic composite PCMs. Initially, paraffin/nano-Fe3O4 composite PCMs with different mass fractions were prepared using the two-step method. Subsequently, an experimental system was constructed to generate a stable rotating magnetic field for evaluating the effectiveness of the proposed method. In this system, the composite PCMs were filled into a beaker with constant power heating at the bottom. The temperature variations within the composite PCMs were compared with and without the application of the magnetic field. Additionally, the effects of the mass fraction of nanoparticles and the rotational speed of the magnetic field on the melting behavior of the composite PCMs was studied, considering parameters such as temperature response rate, liquid fraction, average temperature, complete melting time, thermal storage capacity, and thermal storage power. The results demonstrated that the complete melting time of the composite PCMs initially decreased and then increased with an increase in the mass fraction of nanoparticles, while it decreased with an increase in the rotational speed of the magnetic field. When the mass fraction was 0.5 wt% and the rotational speed was 200 rpm, the complete melting time was reduced by 9.19 %.