Numerical investigation on a latent thermal energy storage with aluminum foam

In this paper, a numerical investigation on Latent Heat Thermal Energy Storage System (LHTESS) based on a phase change material (PCM) in a metal foam is accomplished. A vertical shell and tube LHTESS made with two concentric aluminum tubes is investigated. The internal surface of the hollow cylinder is at a constant temperature above the PCM melting temperature to simulate the heat transfer from a hot fluid. The other external surfaces are assumed adiabatic. The phase change of the PCM is modeled with the enthalpy porosity theory while the metal foam is considered as a porous media that obeys to the Darcy-Forchheimer law. Local thermal nonequilibrium (LTNE) model is assumed to analyze the metal foam and some comparison are accomplished with the local thermal equilibrium model assumption. The governing equations are solved employing the Ansys-Fluent 15 code. Numerical simulations for PCM, PCM in the porous medium in LTE and in LTNE assumptions are obtained. Results as a function of time for the charging phase are carried out for different porosities and assigned pore per inch (PPI). The results show that at high porosity the LTE and LTNE models have the same melting time while at low porosity the LTNE has a larger melting time. Moreover, the presence of metal foam improves significantly the heat transfer in the LHTESS giving a very faster phase change process with respect to pure PCM, reducing the melting time more than one order of magnitude.