Abstract
There is an enormous need in the health welfare sector to manufacture inexpensive dialyzer membranes with minimum dialysis duration. In order to optimize the dialysis cost and time, an in-depth analysis of the effect of dialyzer design and process parameters on toxins (ranging from tiny to large size molecules) clearance rate is required. Mathematical analysis and enhanced computational power of computers can translate the transport phenomena occurring inside the dialyzer while minimizing the development cost. In this paper, the steady-state mass transport in blood and dialysate compartment and across the membrane is investigated with convection-diffusion equations and tortuous pore diffusion model (TPDM), respectively. The two-dimensional, axisymmetric CFD model was simulated by using a solver based on the finite element method (COMSOL Multiphysics 5.4). The effect of design and process parameters is analyzed by solving model equations for varying values of design and process parameters. It is found that by introducing tortuosity in the pore diffusion model, the clearance rate of small size molecules increases, but the clearance rate of large size molecules is reduced. When the fiber aspect ratio (db/L) varies from 900 to 2300, the clearance rate increases 37.71% of its initial value. The results also show that when the pore diameter increases from 10 nm to 20 nm, the clearance rate of urea and glucose also increases by 2.09% and 7.93%, respectively, with tolerated transport of albumin molecules.
Highlights
During the development of end-stage renal disease (ESRD), a considerable amount of toxins, naturally filtered by human kidneys, begins to accumulate in ESRD patient’s blood
When the patient is suffering from ESRD, hemodialysis is the most inexpensive and effective therapy to remove these solutes from the blood
Low molecular weight solute transport is governed by diffusion
Summary
During the development of end-stage renal disease (ESRD), a considerable amount of toxins (ranging from small to large size molecules), naturally filtered by human kidneys, begins to accumulate in ESRD patient’s blood. When the patient is suffering from ESRD, hemodialysis is the most inexpensive and effective therapy to remove these solutes (toxins) from the blood In this therapy, the blood flows from the patient’s body to an extracorporeal circuit that mimics the function of the human kidney with the help of a hollow fiber dialyzer. The hollow fibers are made of semi-permeable porous membranes with an active surface area of 0.8−2.5 m2 and a diameter of nearly 200 nm [1] These fibers allow convective and diffusive transport of uremic solutes, but resist the transport of albumin and blood cells towards the dialysate compartment. The transfer of middle molecular weight solutes (i.e., endothelin, β2-Microglobulin, β2-microglobulin, complement factor D, albumin) requires convection (ultrafiltration) This transport phenomenon’s efficiency depends on hollow fiber geometry, membrane characteristics, and operating variables [2,3,4]
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