Ultrafiltration thin-channel

Figure 6.9 Ultrafiltration flux with a latex solution at an applied pressure of 60 psi (in the limiting flux region) as a function of feed solution latex concentration. These results were obtained in a high-turbulence, thin-channel cell. The solution recirculation rate is shown in the figure [13]...

The present contribution describes a novel low pressure, high flux system which utilizes an "in situ" dynamically formed silica membrane particularly suited for the ultrafiltration of emulsions. The support for this selective layer of silica was a pleated, thin channel crossflow module il (tradename "Acro-flux", Gelman Sciences, Inc.) containing 0.1 m of 0.2 urn pore size acrylonitrile copolymer membrane. 

Goldsmith (1971) pointed out that developed osmotic pressures for macromolecular solutions were not necessarily negligible. The ultrafiltration of Carbowax 20M (polyethylene oxide) and various Dextrans was studied in thin channel and tube flow as well as stirred batch cell. Both turbulent and laminar flow regimes were considered. Data were analyzed with the use of Eq. (2) and the phenomenological relationship of Eq. (1) with Rg = 0. From Eq. (1) it was possible to calculate an average... 

With the ultrafiltration of macromolecular solutions in cross flow systems such as thin channel or tubular systems it is usually the procedure to measure average flux rates at steady state. Therefore, Eq. (81) may be integrated to give... 

When the assumption of constant wall concentration is justified, data for the unstirred batch cell and thin channel systems may be interpreted using models presented in Trettln and Doshi (1980a, 1980b). Such an analysis is performed where agreement is shown to be very good between theory and osmotic pressure limited ultrafiltration experiments. 

It can be argued that any turbulent flow correlation should not be applied for Re <10,000. However, in current thin-channel ultrafiltration devices, the entrance geometry is such that fully developed turbulent flow occurs at much lower Reynold s numbers. Measurements of fluid velocity versus pressure drop show a definite transition from laminar to fully developed turbulent flow at Re = 2000. 

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