In this study, we investigated the use of unit-cells comprised of nano-scale spherical particles to model the microporous layer (MPL) of polymer electrolyte membrane (PEM) fuel cells. We determined the effective thermal conductivity of various unit-cells based on body-centred cubic (BCC) and face-centred cubic (FCC) orientations, developed for commercially available MPL materials SGL-10BB and SGL-10BC. Informed by previous work done by the authors, unit-cells are constructed with constant particle size and filling radius, while varying the particle separation distance. Here it was found that the effective thermal conductivity of the MPL is heavily dependent on particle spacing due to the high thermal conductivity of the carbon particles. Also, it was found that SGL-10BB unit-cells are slightly more conductive than SGL-10BC. The results of this study can be used in the stochastic representation of the MPL, and can be extended to measurements of oxygen diffusion and electrical conductivity. (C) 2015 Elsevier Ltd. All rights reserved.