UBC Theses and Dissertations

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UBC Theses and Dissertations

Design of a capillary artificial kidney Davis, Harold Robert


An engineering study was made of an artificial kidney— one of the major components used in the treatment of patients suffering from chronic uremia. As the capillary artificial kidney offered the most advantages over other systems, an analysis of the mass transfer and blood flow characteristics of this configuration was attempted with the view towards optimization. It was determined theoretically and verified experimentally that a Newtonian fluid mass transfer analysis is a good approximation even though blood, the fluid dialyzed in the artificial kidney, is non-Newtonian. Measurements taken from a patient undergoing hemodialysis indicated that steady-state conditions for mass transfer can also be assumed. From the mass transfer analysis for a single capillary, the characteristics of a composite dialyzer were determined in terms of certain physiological parameters. The system was optimized by maximizing the mass transfer efficiency with respect to the membrane area. The analysis predicted the best capillary diameter in terms of the operating parameters. It was found that the optimized system had a constant mass transfer efficiency of approximately 70 percent for most operating conditions. A manifold system which would distribute blood to the capillaries uniformly and which would have no regions of stagnation or turbulence was devised. The manifold had a capillary outflow region of rectangular dimensions which was normal to the inlet direction. It was determined that the best manifold shape was circular in cross-section and had a linear decrease in cross-sectional area with manifold length. Utilizing the predicted system configuration for optimum mass transfer and blood distribution, a small version of the artificial kidney was designed and tested.

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