A solid–liquid model based on lattice Boltzmann method for phase change material melting with porous media in cylindrical heat exchangers

Abstract

Phase change materials (PCMs) are widely used in thermal energy storage systems as they can absorb and release a large amount of heat during the phase change process. The numerical study of PCM heat exchangers is an efficient method to analyze PCM behaviors. In this paper, a solid–liquid phase change model is developed based on the lattice Boltzmann method (LBM) to simulate transient phase change in the porous media. This model combines the axisymmetric porous LBM with an enthalpy-updating scheme, which enables it to simulate the axisymmetric porous PCM phase change efficiently. The enthalpy-based LBM at the scale of representative elementary volume is adopted for the modeling of the PCM phase change and the porous media. Moreover, double distribution functions coupled with a multi-relaxation-time scheme are utilized in LBM for the simulation of the fluid flow and temperature field. This improved model is validated using experimental results for a copper-foam enhanced PCM heat exchanger. Validation results indicate that the new model can successfully simulate the temperature glide of the PCM and the effect of natural convection on the PCM temperature field with an error of 10%. A parametric study is then conducted to evaluate the effect of natural convection on PCM melting and results indicate that the average acceleration of PCM melting due to the natural convection can be up to 10%. Based on the validation and parametric study, the new model can predict the performance of the cylindrical PCM heat exchanger. The new model is expected to be applied in a wider field of PCM phase change, which can benefit the design and improvement of PCM heat exchangers in thermal energy storage systems.