The role of porous metal foam on the unidirectional solidification of saturating fluid for cold storage

We conducted analytical, numerical and experimental investigations on solidification of fluid saturated in highly porous metal foams with open cells. Based on pore-scale thermal equilibrium assumption, an analytical extension of the classical Neumann's solution was made to predict phase change heat transfer in PCM-foam composites. To explore the heat transfer mechanisms underlying the phase change process and clarify the role of foam insertion, three-dimensional direct numerical simulations on periodically distributed tetrakaidecahedron cells were carried out. Experimental measurements were performed to validate the analytical model and the numerical method, with good agreement achieved. The phase interface was macroscopically flat via experimental visualization but microscopically irregular via pore-scale simulations. Temperature difference between the saturating PCM and metallic ligaments was negligible, so that local thermal equilibrium and one-equation model were applicable especially at low Ste numbers (e.g., 0.22). The present findings provide new insights to cold energy storage design, utilization and economic analysis in HVAC systems.