Title : Lattice Boltzmann simulation of metal foam porosity effects on phase transition phenomenon in a latent heat storage device
Abstract:
This paper performs a numerical evaluation of the geometric structure of metal foam such as pore density (PPI; number of pores per inch) and porosity effect on melting and solidifying phenomena heat transfer in an open-ended rectangular porous channel (metal foam) contained a phase change material (PCM: paraffin) under forced convection. The local thermal non-equilibrium condition (LTNE) is manifested between phases (thermal field) and the Darcy-Brinkman-Forchheimer model (DBF) for dynamic field. Governing equations are simulated using the thermal single relaxation time (T-SRT) lattice Boltzmann method (LBM) at the representative elementary volume (REV) scale. In this work, the lattice Boltzmann equations (LBE) are based on the D2Q9 model. Fluid flow and the fluid and solid temperatures were simulated via three distribution functions.
The effects of metal foam PPI (10 £ PPI £ 30), porosity ( 0.7 £ e £ 0.9 ) and Reynolds number ( 200 £ Re £ 400) on melting (charging) and solidifying (discharging) phenomena were investigated. Outcomes are presented for the local thermal non-equilibrium parameter and the entropy generation rate for the selected parameters range. Previously, to validate our in-house code, a comparison with other available cases in literature was done. Results show that among the different features of metal foam such as thermal conductivity and porosity, the decrease of the latter and the increase in Re speeds up the melting phenomenon under the unsteady, forced and laminar convection. However, a decrease of PPI for high porosity (=0.9) gives a minimal LTNE value during charging case (melting), but during discharging process (solidification), an increase of PPI for lower porosity (=0.7) decreases the LTNE parameter whatever Re number.
