A clear understanding of flow and heat transfer at pore-scale level in microporous media is a topic of concern in microcooling/heating systems. In this work, a multiple-relaxation-time lattice Boltzmann method (LBM) is employed to study flow and heat transfer of gas in microporous media. Curved boundaries are treated using an effective boundary condition, which is formed by combining nonequilibrium extrapolation with counterextrapolation methods. The method also incorporates velocity slip and temperature jump on gas–solid interface. A two-dimensional (2D) porous domain composed of microcylinders, is considered from a representative element volume (REV) for the simulation. Porosity of the domain is variated by altering diameter of microcylinders. Nusselt number is calculated by varying Knudsen number (0.0–0.1), Reynolds number (5–50) and porosity (0.4–0.8). Based on the obtained numerical predictions, a new Nusselt number correlation is proposed for the first time in this work which can accurately predict the heat transfer for slip gas flow in confined porous media.