Exergy or entropy generation analysis as a tool of applied thermodynamics is becoming standard practice for optimizing energy conversion systems and in identifying the deficiency of a component in a system, Porous media is used to enhance heat transfer in heat exchangers (HE). Also, porous layer adjusted to the inner surface simulates the fouling effect in heat exchangers. Optimizing the heat exchanger inserted with porous media and understanding the fouling effect on the rate of heat transfer and fluid flow is crucial for HE design and operations, which motivate the present work. The present work mainly investigates entropy generation due to flow in a pipe fully or partially filled with porous medium. The pipe is assumed to be isothermal. The porous layer is inserted at the core of the pipe or attached on the inner surface of the pipe. Forced, laminar flow is assumed. The effects of porous layer thickness and permeability of layer on the rate of entropy generation were investigated. Developing and fully developed flow conditions are considered in the analysis. (c) 2005 Elsevier Ltd. All rights reserved.