A hollow rotor core assembly for a wind turbine with at least one set of cylindrical stacks having a plurality of guiding vanes on the internal surface of the cylindrical stacks, having at least one set of air openings to accept airflow into the hollow rotor core for creating when in rotation a vortex inside the hollow rotor core, having at one end a partial blocking device as such to allow the exhaust of only a fraction of the peripheral portion of the vortex and to redirect the remaining central portion of the vortex towards the other end of the hollow rotor core where the bulk of the airflow will be exhausted from the hollow rotor core.