Vol.2, No 1, 1999 pp. 9 - 19
UDC 543.645+542.816+676.014.8
THE EFFECT OF CONCENTRATION DEPENDENT
VISCOSITY ON PERMEATE FLUX LIMITATION IN ULTRAFILTRATION
G. T. Vladisavljević, M. B. Rajković
Institute of Food Technology and Biochemistry, Faculty of Agriculture,
Belgrade University, Nemanjina 6, P.O. Box 127, 11081 Belgrade-Zemun, Serbia,
Yugoslavia
Abstract. Ultrafiltration of macromolecular solutions was analyzed
by using the osmotic-pressure model in which the influence of the solute
concentration on the mass-transfer coefficient is taken into account. A
mathematical analysis of the model clearly shows that an increase of the
solution viscosity with the solute concentration plays the main role in
the existance of a limiting permeate flux at a finite pressure difference.
The membrane resistance has no effect on the limiting permeate flux except
on the value of the pressure difference necessary to reach the limiting
flux. In order to define the Js vs. delta p plots, a system of equations
was derived, the parameters of which are to be experimentally determined.
A simulation results are presented for the ultrafiltration of whey protein
solutions in recirculating UF units under turbulent flow.
Key words: ultrafiltration, flux limitation, osmotic-pressure
model, whey proteins, mass-transfer coefficient
UTICAJ KONCENTRACIONE ZAVISNOSTI VISKOZITETA
NA LIMITACIJU FLUKSA PERMEATA PRI ULTRAFILTRACIJI
Ultrafiltracija rastvora makromolekula je proučavana primenom modela osmotskog
pritiska u kome je uzet u obzir uticaj koncentracije rastvorka na koeficijent
prenosa mase. Matematičkom analizom modela pokazano je da porast viskoziteta
rastvora sa povećanjem koncentracije rastvorka igra glavnu ulogu u javljanju
graničnog fluksa pri konačnoj razlici pritisaka. Otpor membrane ne utiče
na granični fluks permeata, već samo na vrednost razlike pritisaka pri
kojoj se uspostavlja granični fluks. Radi definisanja zavisnosti Js od
?p, izveden je sistem jednačina čiji se parametri moraju odrediti eksperimentalno.
Prikazani su rezultati numeričke simulacije procesa ultrafiltracije rastvora
proteina surutke u protočnim aparatima sa recirkulacijom napojnog toka
pri turbulentnom režimu strujanja.
Ključne reči: ultrafiltracija, limitacija fluksa, model osmotskog
pritiska, proteini surutke, koeficijent prenosa mase
