MASS-TRANSFER IN HOLLOW-FIBER MODULES WITH NONUNIFORM HOLLOW FIBERS

This theoretical paper shows how the average mass-transfer coefficient in a hollow-fiber module can be estimated from the average properties of the hollow fibers. The analysis assumes that each solute diffuses independently, and that solute transport is unaffected by mass-transfe r resistances on the permeate side of the membrane. For polydisperse f iber diameters, the average coefficient is reduced by the polydispersi ty; for polydisperse fiber-wall thicknesses, the average coefficient c an be increased or decreased. The change in this average coefficient d epends on the fraction of solute transferred, i.e. on the 'clearance'. It will have different values for different solutes. The results have bearing on the design of artificial kidneys.