Numerical study on the thermal performance of foam-metal composite phase change material in different force fields

•The end-state isobar depending on the force field is introduced.•The evolution of PCM temperature field is predicted using the end-state isobar.•The negative force field can significantly improve the thermal performance of PCM. To make a better application of phase change material (PCM) in the thermal management of aerospace systems, this paper investigates effects of the variation of foam-metal pore structure on the thermal performance of composite PCM (CPCM) subjected to different force fields. A two-dimensional numerical model based on the enthalpy-porosity method and the two-temperature energy equation is developed and verified with the experimental data. The thermal behavior of CPCM with different porosities (ω = 20 PPI, ε = 0.91, 0.93, 0.95 and 0.97) and different pore densities (ε = 0.95, ω = 10, 20, 40 and 80 PPI) are investigated under centrifugal acceleration conditions of 0, 5 and -5 g, respectively. A novel index of "end-state isobars" is introduced to describe the melting process of CPCM. The results show that the isotherms of CPCM liquid phase evolve gradually towards the interface parallel to end-state isobars in all conditions. At 0 g, decreasing the porosity effectively improves the thermal conduction of CPCM and slows down the approaching of the isotherms to the end-state isobars. Similarly, increasing the pore density significantly weakens the natural convection of liquid PCM and can also slows down the approaching isotherms to the end-state isobars. At 5 g, the isotherms can match exactly with the end-state isobars, after which the heat transfer process mainly depends on conductive. And decreasing the porosity can significantly improve the thermal performance of CPCM, while adjusting the pore density has almost no effect. At -5 g, the natural convection strength of CPCM is enhanced, changing porosity has limited effect on the heat transfer performance of CPCM, while decreasing pore density can significantly enhance the heat transfer performance. The results may provide some valuable reference for the evaluation and design of latent heat thermal energy storage (LHTES) system suitable to the aerospace field.