At the free end 4a of the shaft 4, the separation element 5 has an end portion 64, which protrudes into the free end 4a. The fluid-guiding portion 11 leads into the end portion 64, so that the cooling fluid can pass through a cylindrical feed element 65 into the first shaft portion 8. The end portion 64 is sealed off similarly to the termination element 42 by a sealing means 66 in the form of an O-ring, which is arranged in a radial groove 67 running in the circumferential direction, and is sealed off by means of a sealing means 68 in the form of an adhesive layer arranged on a roughened surface 69 of the end portion 64.

In this exemplary embodiment, the termination element 42 is not formed as a blind stopper, but instead has a passage for a further feed element 70, in order to guide the cooling fluid out from the second shaft portion 9 after said cooling fluid has been introduced into the fluid-guiding portion 11 and has passed through the cooling channel arrangement 13. Similarly to the first exemplary embodiment, the direction of the cooling fluid flow can be reversed in this exemplary embodiment as well.