A boundary layer turbomachine, comprising: a housing defining an interior space and having an inlet opening and an outlet opening to facilitate movement of a fluid through the housing; and a rotor assembly disposed in a rotor chamber and configured to rotate about an axis of rotation, the rotor assembly having a plurality of disks spaced apart along an axis of rotation to provide gaps between the disks, the plurality of disks defining an interior opening along the axis of rotation, and a disk carrier disposed at least partially in the interior opening in support of the plurality of disks, the disk carrier having a fluid passageway exposed to two or more of the gaps between the disks, wherein the fluid passes through gaps between the disks and the interior opening as the fluid moves through the housing and characerised in that the boundary layer turbomachine further comprises a partition circumferentially dividing the interior space into an outer chamber and a rotor chamber located radially inward of the outer chamber, the partition having partition openings such that fluid is movable through the partition between the outer chamber and the rotor chamber. a housing defining an interior space and having an inlet opening and an outlet opening to facilitate movement of a fluid through the housing; and a rotor assembly disposed in a rotor chamber and configured to rotate about an axis of rotation, the rotor assembly having a plurality of disks spaced apart along an axis of rotation to provide gaps between the disks, the plurality of disks defining an interior opening along the axis of rotation, and a disk carrier disposed at least partially in the interior opening in support of the plurality of disks, the disk carrier having a fluid passageway exposed to two or more of the gaps between the disks, wherein the fluid passes through gaps between the disks and the interior opening as the fluid moves through the housing and characerised in that the boundary layer turbomachine further comprises a partition circumferentially dividing the interior space into an outer chamber and a rotor chamber located radially inward of the outer chamber, the partition having partition openings such that fluid is movable through the partition between the outer chamber and the rotor chamber. axis of rotation, the rotor assembly having a plurality of disks spaced apart along an axis of rotation to provide gaps between the disks, the plurality of disks defining an interior opening along the axis of rotation, and a disk carrier disposed at least partially in the interior opening in support of the plurality of disks, the disk carrier having a fluid passageway exposed to two or more of the gaps between the disks, wherein the fluid passes through gaps between the disks and the interior opening as the fluid moves through the housing and characerised in that the boundary layer turbomachine further comprises a partition circumferentially dividing the interior space into an outer chamber and a rotor chamber located radially inward of the outer chamber, the partition having partition openings such that fluid is movable through the partition between the outer chamber and the rotor chamber.