Empirical correlation equations for the average Nusselt number have been determined that accurately represent an extensive body of new experimental data for the geometry under consideration for fully developed thermal conditions. The equations cover the Darcy, Forchheimer and turbulent regimes of flow. The correlation equations are based upon a hypothesis that regards the flow in a porous medium to be the superposition of a ’fine’ component upon a ’coarse’ component and takes into account the wall effect and dispersion. The results show that packed tubes provide heat transfer rates from two to seven times those of unpacked tubes for laminar Row and two to two and a half times for turbulent flow for equal pumping power.