Mass Transfer in Hemodialyzers cf. Section

In the situation where the effect of filtration - that is, water movement across the membrane due to the difference in hydrostatic pressure and/or osmolarity - can be neglected, the overall resistance for mass transfer in hemodialyzers with flat 

Many membrane materials have been developed and are used for hemodialyzers. Today, these include regenerated cellulose, cellulose acetate, polyacrylonitrile, poly(methylmethacrylate), vinyl alcohol-ethylene copolymer, polysulfone, 

The relative magnitudes of the three terms on the right-hand side of Equation 14.25 vary with the diffusing substance, the flow conditions of both fluids, and especially with the membrane material and thickness. With the hollow-fiber-type hemodialyzers that are widely used today, the membrane resistance usually takes a substantial fraction of the total resistance, and the fraction increases with the increasing molecular weight of the diffusing component. 

One widely used performance index of hemodialyzers is that of clearance, defined similarly to that of the human kidney. The clearance of a hemodialyzer is the conceptual volume of blood (ml min-1) from which a uremic substance is completely removed by hemodialysis. Let Qg (ml min-1) be the blood flow rate through the dialyzer, Qp (ml min-1) the dialysate flow rate, and CB and CD (mg cm-3) the concentrations of a uremic substance in blood and dialysate, respectively, with the subscripts i and o indicating values at the inlet and outlet, respectively. The rate of 

Another index of hemodialyzer performance is the dialysance (ml min-1), defined as  

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