High-performance tangential flow

Zydney, A.L. and van Reis, R., High performance tangential flow filtration, in Membrane Separations in Biotechnology, 2nd edn., W.K. Wang, (Ed.), Marcel Dekker, New York, 2001, pp. 277-298. 

R. van Reis, J.M. Brake, J. Charkoudian, D.B. Bums, A.L. Zydney, High performance tangential flow filtration using charged membranes, J. Membr. Sci. 159(1999) 133-142. 

HPTFF high-performance tangential-flow filtration... 

Van Reis et al. (1999) found that high separation factors for solute species with size differences less than an order of magnitude were obtainable using high-performance tangential-flow filtration. Their results indicate that maintaining a constant transmembrane pressure drop across the entire length of the membrane leads to a much finer fractionation of proteins. 

Comparing Figures 20.5a and 20.5b it can be seen that the sharpness of the virus particle fractionation is better with the 0.1-pm pore size membrane. Since membranes have a pore size distribution, development of a practical membrane-based fractionation step will depend on careful selection of an appropriate membrane pore size and pore size distribution. Further it is likely that operating methods such as high-performance tangential-flow filtration may improve the sharpness of the fractionation. 

Asymmetric membranes have a tight, low-permeability, retentive zone that performs the desired separation and a more open, high-permeability zone that provides mechanical strength to the overall membrane. This structure is particularly critical to the economic viability of reverse-osmosis membranes. Asymmetric membranes operated in TFF mode must have the tight side facing the feed channel so that particles are retained on its surface and can be acted upon by the tangential flow. Asymmetric membranes operated in NFF mode can... 

Valve-Less Rectification Pumps, Figure 6 A simple version of the vortex diode. At left is the closed state with rotation in the vortex chamber at right is the easy flow, open state with radial forward flow. High-performance diodes have several tangential inlets info the chamber, resulting in symmetric character of the flow - but lead to an even more difficult spatial layout of the rectifier circuit... 

Alternatively, in transient flows the slip parameter can also be determined using the time position of the maximum of the experimental fimctions (tT for tangential stress and tN for normal stress). However, this can only be performed accurately if the stress overshoot is large enough to avoid uncertainties in these values and this can only be achieved at high shear rates. In this case, according to equations (50c) and (50d) ... 

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