Flow visualization in a dialyzer
Flow patterns of blood through a dialyzer are crucial factor to achieve efficient hemodialysis. For a better insight in dialyzer efficiency with respect to low blood flow hemodialysis, fluid flow patterns in a dialyzer were visualized. Flow in hollow fibers at various flow rates was observed with ultrasound echo from microbubles generated in water or 30% glycerin solution which simulated blood, and evaluated with the images at different times, Although fluid in hollow fibers in both central and peripheral portions of a dialyzer flowed uniformly at a high flow rate, flow in the peripheral portion became slower compared to that in the central portion at lower flow rates. Flow distribution in both headers in a dialyzer was also visualized with laser scattering from skim-milk particles in 30%glycerin solution. In the inflow header space, the jet flow from the inlet collided against the center of the surface consisted of the ends of hollow fibers, went outward and caused large eddies around the two-thirds from the radial terminal of the inflow header. Besides, small eddies were occurred right outside of the large eddies. These flow disturbances might cause the pressure difference between the central and peripheral portions in the header space, and lead to the inhomogeneous flow in hollow fibers, which was observed in slower flow rates. On the other hand, in the outflow header space, solution from the end of hollow fibers flowed to the outlet of the dialyzer at increasing rates as the outflow header became narrower toward to the outlet, and eddies or other disturbed flow were not observed.
Departmental Bulletin Paper