Hollow fiber dialysers of a common design have a cylindrical fiber bundle that is arranged, in a cylindrical filter housing. Blood flows through the inside of the fibers, and the dialysate flows in the area between the fibers and the filter housing in a counter flow to the blood. The task of a dialyser is the exchange of matter through the wall of the hollow fibers. The blood usually flows at an even velocity within all fibers. For an optimum of exchange effect, the dialysate should be constantly exchanged externally of the hollow fibers. This way a permanently high concentration difference between the interior and exterior of the fibers is ensured as the driving force for a diffuse exchange of matter.
In a common design dialyser, both the inflow and outflow of the dialysate is connected with the externally positioned fibers of the fiber bundle. That is why it cannot be ensured initially that all fibers in the fiber bundle are flushed with the same amount of dialysate. If a laminar flow of the dialysate in the dialysate area is assumed, the entire dialysate can theoretically flow through between the fiber bundle and the housing without the dialysate entering into the bundle interior. The exchange surface provided by the hollow fiber bundle would not be utilized in this way. In this case, the dialysate flows on a route of the least resistance from the entrance along the fibers in-relating to the dialyser-axial direction toward the output.
From DE 2851687 C2 it is known that the hollow fibers are designed curled, or crimped for an improved penetration of the hollow fiber bundle by the fluid flowing externally of the hollow fibers.
From U.S. Pat. No. 3,616,928 a matter exchange apparatus with crimped hollow fiber bundles is also known.
An oxygenator is described in EP 314581 B1 that has a hollow fiber membrane bundle in the cylindrical housing that is also crimped.
Crimped or curled fibers of a wavelength of about 28 mm are used in known dialysers. The hollow fibers according to prior art with their crimping or curling are used independently of the geometric conditions of the dialyser.
In order to increase the performance of the dialyser, solution approaches already exist in which other fibers have been added to the dialysis fibers in the bundle.
Other solutions intend to wind or knot small bundles of dialysis fibers with a thread, and to combine these small bundles to large bundles. This should enable an improved through flow of the hollow fiber bundle through the fluid flushing the hollow fibers, i.e., the dialysate in the case of a dialyser.