A pressure regulator also acts as a bypass in case of a blockage in the cooler. A centrifugal pump sends coolant around the external rotor jacketing but via an intricate path in an attempt to even out the massive thermal stresses.
The pressure regulator acts as a bypass for the cooler and is used to manage the thermal stresses on the external rotor casing. The centrifugal pump circulates coolant through an intricate route to distribute it evenly across the system.