A 3D numerical code, based on the finite volume method, able to model the cooling stage of an extrusion line is presented and validated. For this purpose, an analytical solution of a simple heat transfer multi domain problem was developed, the result obtained being compared with the predictions given by the numerical code. A prior study performed with the above mentioned code showed that in general when a reduction of the profile average temperature is imparted, lower temperature homogeneity is also obtained, being the only exceptions the reduction of the extrusion velocity and splitting the calibrator into several units, separated by annealing zones. Therefore, the only way to improve the cooling efficiency without compromising the production rate is to divide the total cooling length into several independent units. In this work that investigation is further extended to study the influence of the individual cooling units and annealing zones lengths distributions on the global cooling efficiency.