The aim of this paper is to determine the shape of a xed-bed reactor which maximizes the conversion rate under the constraints of process model equations (i.e. continuity, Navier-Stokes, and mass balance equations), energy dissipation, iso-volume, and manufacturing. Incompressible uid, laminar ow regime and steady-state conditions in the reactor are the main assumptions taken into account. The optimization method developed is based on the adjoint system method and OpenFOAM framework is used as CFD solver to compute the state vector and its adjoint variables introduced by the optimization approach. The algorithm developed is then tested on two dierent cases, a reactor where a rst order homogeneous reaction takes place and another one involving a surface reaction. The optimization results show a signicant improvement of the conversion rate by 2.7% in the rst case, and by 16% in the second one. Finally, initial and optimal shapes are manufactured using a 3D printing technique.