Numerical simulation of heat transfer performance in an enclosure filled with a metal foam and nano-enhanced phase change material

Nowadays phase change materials are widely used in different engineering systems to perform effective cooling techniques for heat-generating elements or to accumulate the thermal energy effectively. The disadvantage of the phase change material is a low thermal conductivity, but it can be improved using porous media or metal nanoadditives of high thermal conductivity. The present research is devoted to the mathematical simulation of conjugate thermal convection in a closed chamber partially filled with metal foam saturated with nano-enhanced phase change material. The governing equations have been formulated using the Oberbeck-Boussinesq equations with the Stefan problem approach for the liquid phase and the heat conduction equation for the solid phase. The finite difference technique in combination with non-primitive variables has been used for numerical analysis. The developed in-house numerical program has been verified using the grid independence test as well as the experimental and theoretical outcomes of other authors. The effects of the metal foam properties and nanoadditives characteristics on melt behavior and thermal energy transport parameters have been studied. The main attention is paid to the influence of a filling height ratio of the metal foam on the heat transport process. It has been revealed that the impact of the metal foam on thermal dissipation is essentially higher compared to the nanoadditives influence. Therefore, in the case of full height foam, the effect of nanoparticles is weak, but in the cavity with a partial height of the porous medium, NePCM can be melted faster than pure PCM and has a negative effect on the heater temperature. It has been also found that changing the filling height ratio from 0.167 to 0.5 does not lead to a significant change in the temperature of the heater.