The cooling of the generator’s stators and rotors is accomplished by circulating water, hydrogen or both through stator coils/core and rotor field windings. The gas coolant is circulated by means of a blower which is an integral part of the rotor assembly.  This paper discusses how the heat exchanger/cooler is modelled using CFD (computational Fluid Dynamics) as a porous medium and the associated boundary conditions. The results are validated from the benchmark pressure drops observed in similar generators.