Analysis of a tubular haemodialyser-effect of ultrafiltration and dialysate concentration

A theoretical analysis has been made of mass transfer in a hollow-fibre artificial kidney with ultrafiltration for: (i) a constant dialysate concentration and (ii) a variable dialysate concentration along the tube length. The latter is a conjugated boundary-value problem. The solution is obtained by the method of separation of variables using an infinite series expansion considering the fluid to be dilute and Newtonian. Results indicate that the ultrafiltration rate, permeability of the membrane and the nonzero dialysate concentration all have a significant effect on the clearance of the solute. The tubular diameter and length have very little effect on the clearance of the solute for a constant membrane surface area, ultrafiltration rate and a low membrane permeability. At high ultrafiltration rates, the effect of the solute concentration in the dialysate phase on the clearance become negligible. This analysis is compared with those of Popovich et al. (1971), Ross (1974) and Cooney et al. (1974). © 1977 International Federation for Medical & Biological Engineering.