Instantaneous melting of ice is accelerated inside a horizontal rectangular cavity with two vertically arranged cylinders using metallic porous matrix made of Ni-Steel alloys. The enthalpy-based lattice Boltzmann method (LBM) with a double distribution function (DDF) is employed at the representative elementary volume (REV) scale. Single-phase model is used and there is a local thermal equilibrium between porous structure and ice. Inserting metallic porous material into the base PCM results in the enhancement of the heat conduction and weakening of the natural convection flow. Concentric pattern of the solid–liquid interface persists in porous samples comparing to the pure PCM melting. Reducing porosity causes decrease of the full melting time and thermal storage capacity of the system. Thermal conductivity ratio has to be enlarged in porous samples with higher porosity from energy saving viewpoint
