Enhanced Natural Convection for Accelerating Melting of Phase Change Material in Cellular Structure through Inserting Fin

The design of thermal conductivity enhancers (TCE) is quite critical to overcoming the disadvantage of the poor thermal conductivity of phase change materials (PCM). The main contribution of this study is firstly to discuss how to actively enhance natural convection of the melted PCM in cellular structure by the fin formed in the structure under the condition of the same metal mass, apart from simultaneously improving heat conduction, which can boost the heat transfer performance. Also, a tailored hybrid fin-lattice structure (HFS) as TCE is designed and fabricated by additive manufacturing (AM). A two-equation numerical method is applied to study the heat transfer of the PCM, and its feasibility is validated with the experimental data. The numerical results indicate that enhanced natural convection and improved heat conduction can be obtained simultaneously when a well-designed fin is embedded into a lattice structure. The enhanced natural convection results in the improved melting rate and the decreased wall temperature; e.g., the complete melting time and the wall temperature are reduced by 11.6% and 19.7%, respectively, because of the fin for metal aluminum. Moreover, the parameters of HFS including the porosity, pore density, and fin dimension have a great impact on the heat transfer. The enhancement effect of the fin for HFS on the melting rate of the PCM increases as the thermal conductivity of the base material decreases. For example, when the fin is introduced into the lattice structure, the complete melting time is reduced by 24.1% for metal titanium. In summary, this study enables us to obtain a good understanding of the mechanism of the heat transfer and provides necessary experimental data for the structural design of HFS fabricated by AM.