Internal cooling for a flow machine

The steam turbine comprises an outer housing (2) and an inner housing (3). A rotor (5) is provided, which comprises a thrust balance piston (4) and multiple rotor blades rotatably arranged inside the inner housing. The inner housing comprises an inner housing end area formed around the thrust balance piston. A seal (27) is provided, which forms a pressure chamber (29) arranged between the inner housing end area and the outer housing.