Simulation and experimental study on the effect of channeling flows on the transport of toxins in hemodialyzers

Channeling flows are common phenomena that exist on the dialysate side in hemodialyzers, and they significantly affect the performance of hemodialyzers. Today, the effect of channeling flows on the clearance of uremic toxins has been studied only experimentally and not theoretically because of its complexity. In this paper, we for the first time introduced a method to mimic channeling flows and, thus, quantitatively investigated the impact of channeling flows on the transport of toxins. The experimental results show that the effect of channeling flows is more significant when the dialysate flow rate is low. The theoretical results show that the flow velocity and toxin concentration fields under channeling flows are qualitatively consistent with the ones published in the literature. Channeling flows induced by the non-uniformity in the hollow fiber packing density can significantly affect the toxin concentration profiles on both dialysate and blood sides and, thus, decrease the clearance of toxins. The effect of channeling flows on the toxin transport is more significant when the fiber packing density is low. The method developed here can be embedded into various theoretical models to match more closely the calculated toxin clearance to reality or to optimize the dialysate flow profiles in hemodialyzers.