Numerical and experimental studies of mass transfer in artificial kidney and hemodialysis

Artificial kidney is a hollow-fiber membrane system, used to remove uremic toxins and excess water from the blood of end-stage-renal-failure patients. Accurate membrane transport data are needed to optimize the design of artificial kidney. A new experimental system was developed to measure the transport properties of hollow fiber membrane, such as hydraulic permeability, solute diffusive permeability and reflection coefficient. A mini-module dialyzer was constructed with a length of 15cm, a diameter of 1.2cm, and 10 hollow fibers inside. A syringe pump was used to ensure steady flow in blood side. This experimental system was used to measure the hydraulic permeability, solute diffusive permeability and reflection coefficient of four uremic-solute markers for four different hollow-fiber membranes typically used in artificial kidneys.; Computer simulation of an artificial kidney offers a time- and cost-saving alternative to study mass transfer in the artificial kidney. This study presented two modified numerical models: equivalent annulus model and porous media model. In the equivalent annulus model, the flow in the artificial kidney is treated as the flow in a fictitious duct with symmetrical boundary. Navier-Stokes (N-S) equations were employed to simulate the blood flow and dialysate flow, Kedem-Katchalsky (K-K) equations were used to simulate the permeating flux across the membrane, and N-S and K-K equations were coupled together in the process of computing. The non-uniformity of the flow distribution of the dialysate was considered in a porous media model, where the dialysate flow was treated as the filtrate in the heterogeneous porous media. Darcy equations were employed to simulate dialysate flow, N-S equations were employed to simulate blood flow, and K-K equations are used to compute the permeating flux across the membrane. Numerical results were consistent with experimental results. The distribution of velocity, pressure and solute concentration is discussed and analyzed, which can provide deep insight into the flow distribution in artificial kidney and help design optimal artificial kidney. All simulations and experiments are performed in aqueous solution. Finally, kinetic modeling and computer software were developed and investigated to prescribe adequate dose for clinically treating patients with acute and chronic kidney diseases.