Macroscale Modeling of Solid–Liquid Phase Change in Metal Foam/Paraffin Composite: Effects of Paraffin Density Treatment, Thermal Dispersion, and Interstitial Heat Transfer

This work focuses on macroscale modeling of solid–liquid phase change in metal foam/paraffin composite (MFPC), addressing the treatment of paraffin density (under distinct paraffin filling conditions in metal foam), thermal dispersion effect, and influence of thermal diffusion-dominated interstitial heat transfer. To this end, a macroscale thermal non-equilibrium model for melting in MFPC with fluid convection is developed by employing the enthalpy-porosity technique and volume-averaging approach. Meanwhile, visualized experiments on the melting of the MFPC sample are carried out to validate the modeling results. Comparing the numerical modeling and experimental visualization results, it is found that for MFPC with an initially saturated filling condition in metal foam using solid paraffin, the varied paraffin density is preferred to be employed for developing accurate phase change model. However, for MFPC that can be just filled with liquid paraffin after melting (i.e., non-saturated filling condition using solid paraffin), the Boussinesq approximation is preferred to achieve satisfying phase change simulation. Thermal dispersion effect in MFPC is proved to be negligible, which should not be overvalued to avoid inducing physical distortions of heat transfer and fluid flow. Consideration of diffusion-dominated interstitial heat transfer in the thermal non-equilibrium model is vital to accurately capture phase interface evolutions as well as to reasonably simulate the mushy zone of paraffin, and the model only incorporating the convection-induced interstitial heat transfer will predict quite inaccurate phase change process. This study can provide useful guidance in macroscale modeling of phase change in MFPC associated with the thermal energy storage applications.