Cooling or heating of bearings in a centrifugal separator

A centrifugal separator comprising:

• a frame;
• a centrifuge rotor enclosing a separation space, said centrifuge rotor being adjoined to a hollow spindle supported by the frame by at least one bearing device, an interior of the hollow spindle in thermal contact with said at least one bearing device;
• a stack of separation discs within the separation space;
• and
• the spindle configured to rotate the centrifuge rotor in relation to the frame around an axis of rotation, wherein the interior of the hollow spindle comprises:
• an inner wall and an outer wall spaced radially from the inner wall;
• a thermal transfer medium inlet for supplying a thermal transfer medium to said interior and a thermal transfer medium outlet for withdrawing said thermal transfer medium from said interior;
• a divider between the inner wall and outer wall of the spindle to create a first flow channel and a second flow channel, the divider directing thermal transfer medium from said thermal transfer medium inlet to said thermal transfer medium outlet in a first direction along a length of the spindle and in a second direction along the length of the spindle, wherein said second direction is opposite said first direction;
• and
• a wall extending between the inner wall and an outer wall of the spindle, the wall extending between the inner wall and an outer wall of the spindle being spaced above the divider to create a transition zone between the first flow channel and the second flow channel,
• wherein said first or second direction is along an inner wall of said interior of the spindle, said inner wall being arranged to rotate during operation of the centrifugal separator.