The aim of this work is to present results obtained through a multi-physics solver used to numerically determine the thermal behaviour of an open-cells metal foam in the case of natural convection. Particular attention is addressed to the right geometry definition in order to capture the intrinsic foam characteristics, thus, the elementary cell used for describing the unitary metal foam one is the tetrakaidecahedron. In addition, in order to improve its isotropy, a random deformation on the basic structure has been introduced. This feature allows to locally deviate flow paths with obvious benefits in terms of heat exchange, with reducing preferential paths arising while packing the elementary cell over the volume. This mesh generation approach is coupled with a hybrid solver based on the lattice Boltzmann framework for the fluid-dynamics field reconstruction and on finite volume method for solving the energy equation so to retrieve temperature evolution. For the first time, high order differencing scheme are used in temperature discretization with obvious benefits in computational accuracy. Numerical results are compared with a set of experimental data available for a range of Rayleigh numbers and for different foam geometries. The agreement between numerical and experimental data is satisfactory with positive outcomes for future model developments. (C) 2017 Elsevier Ltd. All rights reserved.