The effect of porous inserts on forced convection in a circular pipe is investigated numerically. Two configurations are considered: A porous material is inserted at the core of the pipe, and an annulus porous material is attached to the inner wall. The flow inside the porous material is modeled using the Darcy–Brinkman–Forchheimer model. Effects of porous thickness, Darcy number, and thermal conductivity on the Nusselt number are investigated. In the first configuration, increasing porous thickness increases Nusselt number, and the value of porous thickness that maximizes Nusselt number varies from 0.8 to 0.95 as the value of Darcy number decreases from 10⁻³ to 10⁻⁶. In the second configuration, for low values of thermal conductivity, increasing the porous thickness decreases Nusselt number, and the porous thickness that achieves the lowest Nusselt number varies from 0.6 to 0.85 as the value of Darcy number decreases from 10⁻³ to 10⁻⁶. However, for high values of thermal conductivity, increasing porous thickness increases Nusselt number. At the expense of reasonable pressure drop, optimum thickness of porous material is found to be 0.6, which maximizes Nusselt number in the first configuration and minimizes it in the second configuration.