Numerical Investigation of Metal Foam Pore Density Effect on Sensible and Latent Heats Storage through an Enthalpy-Based REV-Scale Lattice Boltzmann Method

Abstract

In this work, an unsteady forced convection heat transfer in an open-ended channel incorporating a porous medium filled either with a phase change material (PCM; case 1) or with water (case 2) has been studied using a thermal lattice Boltzmann method (TLBM) at the representative elementary volume (REV) scale. The set of governing equations includes the dimensionless generalized Navier–Stokes equations and the two energy model transport equations based on local thermal non-equilibrium (LTNE). The enthalpy-based method is employed to cope with the phase change process. The pores per inch density (10≤PPI≤60) effects of the metal foam on the storage of sensible and latent heat were studied during charging/discharging processes at two Reynolds numbers (Re) of 200 and 400. The significant outcomes are discussed for the dynamic and thermal fields, the entropy generation rate (Ns), the LTNE intensity, and the energy and exergy efficiencies under the influence of Re. It can be stated that increasing the PPI improves the energy and exergy efficiencies of the latent heat model, reduces energy losses, and improves the stored energy quality. Likewise, at a moderate Re (=200), a low PPI (=10) would be suitable to reduce the system irreversibility during the charging period, while a high value (PPI = 60) might be advised for the discharging process. As becomes clear from the obtained findings, PPI and porosity are relevant factors. In conclusion, this paper further provides a first analysis of entropy generation during forced convection to improve the energy efficiency of various renewable energy systems.

A State of the Art Review on Sensible and Latent Heat Thermal Energy Storage Processes in Porous Media: Mesoscopic Simulation

“…More details can be found in Refs. [48,114,118,119]. Generally speaking, natural convection is considered in certain circumstances and is sometimes negligible to simplify the mathematical model.…”

“…Among the different characteristics of a sensible storage medium, the porosity effect, which turned out to be a crucial characteristic, is sketched herein. To address this topic, Mabrouk et al [48] developed a numerical model to study the effect of pore density parameter (PPI) on an SHS unit. The system deemed was subjected to forced convection and compared to an LHS unit.…”

The Application of REV-LBM Double Mesh Local Refinement Algorithm in Porous Media Flow Simulation

“…Therefore, GLBE-based REV-scale LBM provides an effective simulation method for the unified simulation of transscale seepage in porous media with micro-nano pore-throat structure. However, even so, shown by numerical simulation results, when simulating the seepage problem related to tight porous media with low permeability, the large velocity gradient generated by the wall boundary (near the fixed structure) or the fracture boundary (junction of the matrix-fracture system) will cause nonphysical oscillation in the boundary region when the calculation nodes are insufficient, thus leading to false perceptions of flow field and restricting the simulation size shown as chapter 4.1 in the reference [21]. Usually, the nonphysical oscillations caused by a lack of nodes can be solved by refining blocks or locally refining nodes to increase the nodes in rapidly varied boundary areas, in which the local refinement approach has more practical benefits.…”