It is indicated that the solder joint of the metal fibrous materials is a critical factor impacting the heat conduction. To reveal the mechanism by which solder joint sizes, solder joint skips, solder flux materials, and filling media affect the thermal conductivity of fibres, pore-scale numerical simulation is employed to study the thermal transport in two-directional (2-D) random fibres. Satisfactory agreement with existing data validates the numerical model. The dimensionless effective thermal conductivity (ETC) of the porous fibres increases with the solder joint sizes. As the solder joint size (i.e., solder joint ratio) increases by 3.06%, the in-plane (k_e-in) and out-of-plane (k_e-out) dimensionless ETC increase by 9.0% and 437.2%, respectively. However, the solder joint skips will weaken the thermal conductivity of the fibres. For the same fibre, the ETC of the fibre increases as the thermal conductivity of solders increases. Further, when the dissimilarity in thermal conductivity between the filling medium and the fibre is reduced, the fibre is less affected by the solder joint skips. Finally, it should be supplemented that the in-plane and out-of-plane ETC (k_e-in and k_e-out) of the fibre without any solder joint are reduced by an average of 14.3% and 98.8%, respectively.

Solar energy, as a kind of renewable energy, offers a large reserve to be harvested at a reasonably low cost for engineering applications. To decouple the temporal and spatial relevance of the continuous energy supply of solar energy, latent heat thermal energy storage can deal with this problem at different temperatures. Aiming to improve energy efficiency, a novel hybrid metal foam-pin fin structure is designed and assessed. Upon conducting measurements on a well-designed experimental bench, the phase change processes of paraffin that is filled in fins, metal foam, and a combination of both (hybrid structure) are evaluated. During the experiments, the transient melting interface is snapshotted and temperature development is documented under five different heat source temperatures of 61 °C, 63 °C, 65 °C, 68 °C, and 70 °C. In the foreground of the novel hybrid structure, each segment of the hybrid is also justified and discussed. Results indicate that the hybrid structure augments marked heat transfer. Compared to pure PCM, complete melting time decreases by 63.4% and simultaneously the temperature response rate increases by 143.9% as implementing the hybrid. Attempts to design hybrid structure find a solution to assess and operate thermal storage applications for solar engineering.