CFD Analysis of Blood Flow Through a Dialyzer Hollow-Fibre Bundle

Abstract

Hemodialysis is a vital medical treatment for patients with renal failure, in which metabolic waste products and excess fluids are removed from the blood using a dialyzer containing thousands of semi-permeable hollow fibres. The hydrodynamic behaviour of blood flow within these fibres plays a crucial role in determining dialysis efficiency and patient safety, as non-uniform velocity distribution, excessive pressure drop, and elevated shear stress may lead to hemolysis and platelet activation. Experimental investigation of flow behaviour inside hollow-fibre dialyzers is challenging due to the small fibre dimensions and dense packing arrangement, making computational fluid dynamics (CFD) a suitable analysis tool. In this study, CFD simulations were performed to investigate steady-state blood flow through a single hollow fibre representing a dialyzer fibre bundle. Blood was modelled as an incompressible, laminar, Newtonian fluid using ANSYS Fluent, with an inlet velocity of 0.01 m/s and physiological material properties. The results show a fully developed laminar velocity profile with a maximum axial velocity of approximately 0.037 m/s at the fibre centreline. A smooth pressure gradient was observed along the fibre length, with an overall pressure drop on the order of 0.4-1.7 Pa depending on inlet and outlet locations. The absence of flow separation, recirculation, or abrupt pressure fluctuations indicates stable hydrodynamic conditions and low shear stress levels within the fibre. Overall, the numerical findings demonstrate that the selected operating conditions produce favourable flow characteristics with minimal risk of blood damage. This study confirms the applicability of CFD as a reliable tool for analysing blood flow behaviour in hemodialysis devices and provides quantitative insight that can support safer and more efficient dialyzer design.