Pump unit, pump system, and pump system operation method

A pump unit comprising:

• a rotation shaft;
• a motor configured to cause the rotation shaft to rotate;
• an impeller mounted on the rotation shaft;
• a housing including a motor chamber housing that defines a motor chamber in which the motor is accommodated and a motor pump chamber housing that defines a pump chamber in which the impeller is accommodated;
• and
• a mechanical seal mounted on the rotation shaft and the housing in an arrangement for sealing the motor chamber with respect to the pump chamber,
• wherein
• the rotation shaft extends into the motor chamber and into the pump chamber;
• the motor includes:
• a rotor mounted on the rotation shaft, and
• a stator that directly faces the rotor in a radial direction of the rotation shaft and is configured to cause the rotor to rotate;
• the motor chamber housing includes:
• a motor chamber outer wall that separates the motor chamber from an environment outside the housing, and
• a gas introduction port, disposed in the motor chamber outer wall, and configured to allow introduction into the motor chamber of hydrogen gas;
• the pump chamber housing includes a pump chamber outer wall that separates the pump chamber from the environment outside the housing;
• the housing includes:
• a suction port, disposed on a side of the pump chamber outer wall, and configured to allow, during rotation of the impeller, liquid hydrogen to be suctioned into the pump chamber,
• a discharge port, disposed on a side of the motor chamber outer wall, and configured to allow the liquid hydrogen to be discharged, and
• a guiding flow line configured to guide a discharge flow of the liquid hydrogen from
• the pump chamber to the discharge port;
• the guiding flow line includes:
• a pump chamber guiding flow line that is disposed in the pump chamber outer wall and extends from the pump chamber to a pump chamber guiding flow line termination, and
• a motor chamber guiding flow line that is disposed in the motor chamber outer wall and extends from the pump chamber guiding line termination to the discharge port;
• the gas introduction port is configured to be connectable to an external gas line capable of extending to hydrogen gas in a reservoir tank;
• and
• the suction port is configured to be connectable to an external suction flow line capable of extending to liquid hydrogen in the reservoir tank.