Computational Fluid And Mass Transport On
Macro And Micro Scales In An Artificial Kidney
Author(s)
S. Eloot & P. Verdonck
Abstract
The evaluation of dialyzer geometry was obtained by investigating transport
processes and fluid properties inside the dialyzer. With computational fluid
dynamics (CFD), a macroscopic as well as a microscopic model of the dialyzer
was developed.
Blood and dialysate flow distributions were calculated in a macroscopic
numerical model of a low flux hollow fiber dialyzer. Computer simulations were
compared to flow field SPECT visualizations (Single Photon Emission
Computerized Tomography). The derived local fluid velocities were further
implemented in a three-dimensional microscopic computer model of a single
hollow fiber with its surrounding membrane and dialysate compartment.
Different equations govern blood and dialysate flow (Navier-Stokes), radial
filtration flow (Darcy), and solute transport (convection-diffusion). Blood was
modeled as a non-Newtonian fluid with a viscosity varying both in radial and
axial direction. Dialysate flow was assumed as a laminar Newtonian flow with
constant viscosity. The permeability characteristics of the asymmetrical
polysulphone membrane were calculated from laboratory tests for forward and
backfiltration.
The model was calibrated and validated in order to accurately calculate water
removal as well as mass transport of small (urea) and middle molecules (vitamin
B12 and inulin). Furthermore, the present microscopic CFD model was used to
investigate the impact on the mass removal of dialyzer geometry and flow
distributions.
Keywords: dialyzer, ultrafiltration, backfiltration, mass transport, convection
diffusion, viscosity model, hemoconcentration, CFD.
Keywords
dialyzer, ultrafiltration, backfiltration, mass transport, convection
diffusion, viscosity model, hemoconcentration, CFD.
Related Book
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