An extension of a simplified model for the effective thermal conductivity (ETC) of open-cell porous foams, that originally contained only one adjustable parameter, is proposed in this article. The present improved model consists of two adjustable parameters those can be calculated directly from detailed numerical predictions of the ETC under vacuum condition and in presence of a reference fluid with known thermal conductivity ratio (of fluid and solid phases). The performance of present simplified model is evaluated by comparing its estimations with results obtained from detailed numerical simulations, those take into account the true morphology of porous media, as well as predictions obtained from the original simplified model, for the complete range of thermal conductivity ratios, lower than unity (0 <= k(f)/k(s) <= 1). Geometries of porous media are either synthetically generated for idealized regular structures or obtained from high resolution three-dimensional computed tomography-scan images for real foams. The present study clearly demonstrates that the proposed simplified model yields extremely accurate estimation of the ETC for all the investigated structures, as long as the reference thermal conductivity ratio of fluid and solid phases is judiciously chosen. (C) 2014 Elsevier Ltd. All rights reserved.