Simulation and experimental investigation of phase change materials within porous metal structures with gradient porosity

As the global economy steadily develops and the rapid growth in industrialization increases, the world is gradually moving towards a serious energy crisis, and finding effective energy utilization methods becomes a consensus. Phase change materials (PCMs) have a wide range of applications in thermal energy storage due to their advantages of high thermal storage density, good cyclic performance, low cost, and environmental friendliness. In this work, the phase change process of the paraffin in uniform and gradient porous metal structures is investigated by simulation and experiments. Thermal storage units combined with paraffin and porous metal structures are designed and fabricated by metal 3D printing technology. A numerical model is established to explore the influence of the gradient porosity and heating source location on the melting process of the paraffin within different thermal storage units. To verify the correctness of the numerical model, visualization experiments are carried out to observe the phase change process of the paraffin. Both the simulated and experimental results demonstrate that the gradient porosity and heating source position greatly influence the paraffin's melting behavior in the porous metal structure. Compared to the uniform porous metal structure, the melting time of the paraffin in the gradient porous metal structure under the bottom and left heating mode can be shortened by 11.26% and 6.21%, respectively. The findings of this study are of considerable scientific and technological interest for developing and optimizing composite phase change thermal storage materials.