Experimental investigation of the effect of copper foam pore structure on the thermal performance of phase change material in different centrifugal force fields

In this paper, composite phase change material (PCM) was fabricated by incorporating copper foam into paraffin wax. The effects of porosity (ε = 0.93, 0.95 and 0.97) and pore density (ω =10, 20 and 40 PPI) on the thermal performance of composite PCM were experimentally investigated in positive centrifugal force field (5 g), normal gravity field (0 g) and negative centrifugal force field (-5 g), respectively. The end-state isobar and buoyancy vector are introduced for the description of the heat transfer process. The results show that there are differences in the effects of metal foam pore structure on the heat transfer process of composite PCM under different force field conditions. At 0 g and 5 g, the isotherms of all experimental conditions gradually converge to the end-state isobars, but decreasing the porosity or increasing the pore density can slow down this evolution rate. At -5 g, the evolution of isotherms is mainly influenced by the buoyancy vector, and isotherms with lower porosity or higher pore density are less influenced by buoyancy. It was also found that reducing the porosity effectively shortens the melting time lags along the heat flow flux direction for all force field conditions. However, reducing the pore density at -5 g shortens the melting time lags in both the upper and lower regions in the heat flux direction, while it only shortens that in the upper region at 0 g, and it has no significant effect on that either in upper region or lower region at 5 g. In addition, in the positive centrifugal force field, lowering the porosity can more significantly improve the heat transfer efficiency, while lowering the pore density can more effectively improve the heat transfer efficiency in the negative centrifugal force field.