An investigation has been conducted to study Lorentz effect on nanomaterial behavior within a permeable space including innovative numerical technique namely CVFEM. Iron oxide has been mixed with H2O and porous domain was filled with this nanomaterial. The impacts of the flow and geometric variables on entropy generation along with the heat transfer have been examined. The simulations have been carried out with wide ranges of the magnetic force, permeability and Rayleigh numbers. The outcomes indicate that the Darcy term has inverse relationship with temperature of hot surface. Stronger convection mode and lower exergy loss appear when buoyancy forces augment. Entropy generation goes up with growth of Hartmann number. (C) 2019 Elsevier Ltd. All rights reserved.