Conditions for Determining Small Radial Dialysate Pressure Gradient in a Cylindrical Hollow Fiber Dialyzer

Abstract

By regarding the dialysate flow in a hollow fiber bundle as a flow in a porous medium, the average dialysate pressure of several hollow fibers is numerically determined using the transverse conductivity perpendicular to the hollow fibers and longitudinal conductivity parallel to the hollow fibers. Determination of the dialysate pressure isobars becomes possible if the transverse-to-longitudinal hydraulic conductivity ratio can be obtained experimentally. Since the dialysate fluid flows in the transverse direction at the inlet and outlet, the radial dialysate pressure gradient is enhanced at the inlet and outlet if the transverse conductivity is low. However, even if the transverse conductivity is low, the use of a slender dialyzer suppresses the radial dialysate pressure gradient. If the transverse-to-longitudinal hydraulic conductivity ratio is lower than one-tenth the radius-to-total-length ratio of the cylindrical dialyzer, the radial dialysate pressure gradient is negligible compared to the central axial dialysate pressure gradient.