From a two-phase model for an adiabatic packed bed through which a gas is flowing, a one-phase model is derived without assuming that the solid and gas temperatures are equal. By means of the derivation, a relationship between the axial effective thermal conductivity in the one-phase model and the heat transfer coefficient in the two-phase model is obtained. The validity of this relationship is confirmed using the experimental results of other authors. These results can also be applied to fixed bed chemical reactors if the reaction takes place in or on the surface of the catalyst. Essential to the derivation is the assumption that the thermal capacity of the gas phase can be neglected. For a fluid where this assumption is not valid, a separate derivation, whose assumptions are more restrictive, is presented in the appendix.