The present work aims to analyze the thermal and the energetic performances of an aftertreatment system with unidirectional and periodic reversal flow within the device. To this purpose a single-channel one-dimensional model was developed in order to assess the heat exchange between the aftertreatment system and the exhaust gas. Furthermore, the temperature profiles of the gas and solid phase were computed and the calculated temperatures were adopted to characterize the energy effectiveness of the aftertreatment system. The comparison between different control modes showed an increase in the heat retention efficiency of the system with reverse flow at low engine load conditions. Conversely, the system with passive thermal management presented higher temperatures of the monolith during the warm-up operations. Furthermore, the influence of unburned hydrocarbons oxidation on the effectiveness of the aftertreatment system was evaluated and the significant influence of the cycle time and the monolith length on the system performance was shown. Finally, the gas residence time was evaluated for different operating conditions. Copyright (C) 2008 John Wiley & Sons, Ltd.