Submersible canned motor pump

A method for producing fluids from a subterranean well, the method comprising:

• providing an electrical submersible pump assembly with a motor-pump unit and a seal section, where the motor-pump unit has:
• a motor housing, the motor housing being an elongated member;
• a stator located within the motor housing, the stator having a stator body with an interior cavity extending along a central axis of the stator;
• a rotor assembly located within the interior cavity of the stator, the rotor assembly comprising a rotor shaft, a rotor member, and an intermediate rotor bearing assembly, where the rotor member and the intermediate rotor bearing assembly circumscribe the rotor shaft, and where the rotor shaft is an elongated member that extends along the central axis of the stator;
• an impeller mounted on the rotor shaft and located within the interior cavity of the stator where the impeller circumscribes the rotor shaft and
• a liner located along an interior surface of the interior cavity, the liner being a thin walled member that is secured to the motor housing and hermetically seals the stator body from a wellbore fluid, where the liner has a polygonal cross section;
• lowering the electrical submersible pump assembly into the subterranean well with a deployment string;
• operating the electrical submersible pump assembly to lift production fluids in a direction out of the subterranean well.