Flux, tangential flow

Antifoam concentration, effect on flux, tangential flow filtration, 6l,63f... 

Antifoam type, effect on flux, tangential flow filtration, 6l,62f Assays, largomycin F-II, 135,137 Axial dispersion, estimation of transfer units, 116... 

A common problem of this technique is the gradual decrease in permeate flux associated with membrane clogging or fouling, caused by adsorption or physical deposition of particles and/or macromolecules on membrane pores. Fouling can be minimized by prior clarification (particulate removal) of the feed solution, by the selection of operational conditions that minimize interactions between membranes and macromolecules, by the use of tangential flow, or by performing intermittent back-flushing operations. 

Choi H, Zhang K, Dionysiou DD, Oerther DB, and Sorial GA. Effect of permeate flux and tangential flow on membrane fouling for wastewater treatment. Sep. Pur. Techn. 2005 45(1) 68-78. 

Figure 2. Tetrahymena concentration by tangential flow filtration. Batch size 100 1. Area 15 ft (1.39 m ). Circulation rate 6.0 1/min. Pin/ out 8/6. Final volume 4.5 1. Concentration factor 22. Flux 0.79 l/m min. Recovery initial...

Figure 2.14 Montage of DVO images collected during tangential flow filtration of 5 tm, 10 tm and 20 tm latex particles on an Anopore membrane with 0.02 tm pores. The two rows of images on the top and bottom were collected with a permeate flux (flowing into the page) of 200Lm h and...

Today most vims filtration is conducted in normal flow mode (Bohonak and Zydney, 2005). The main advantage of tangential-flow filtration is the ability to suppress cake formation and the consequent decrease in permeate flux. This results in much larger feed volumes being filtered (capacity) before the module needs to be cleaned. 

Imposition of no-slip velocity conditions at solid walls is based on the assumption that the shear stress at these surfaces always remains below a critical value to allow a complete welting of the wall by the fluid. This iraplie.s that the fluid is constantly sticking to the wall and is moving with a velocity exactly equal to the wall velocity. It is well known that in polymer flow processes the shear stress at the domain walls frequently surpasses the critical threshold and fluid slippage at the solid surfaces occurs. Wall-slip phenomenon is described by Navier s slip condition, which is a relationship between the tangential component of the momentum flux at the wall and the local slip velocity (Sillrman and Scriven, 1980). In a two-dimensional domain this relationship is expressed as... 

Typical flux data with two interpromoter spacings (AL) are shown in Figure 28 as a function of the cross-flow rate. The flux Increased by a factor of 3 for the best case. Though Probstein did not plot his data in this way, it is Interesting to note that the empty channel flux has a predictable 0.33 power dependence on tangential velocity. With the turbulence promoters, the slope shifts closer to the 0.7-0.8 power dependence normally observed in turbulent flow. Unfortunately, data are not available in Probstein s paper on the increased pressure drop associated with the turbulence promoters, but it would appear that the flux to power ratio is greatly improved with turbulence promoters. 

Figure 17.8 shows the probe, which consists of a 1-millimeter diameter t3rpe K thermocouple centered between two 1-millimeter diameter pressure taps. Each of the pressure tubes was bent 90° and sheared at the bend. To obtain a measurement, the tube is rotated until the pressure difference between the two taps is maximized. This is the position at which one tube is directed into the oncoming flow and the other is parallel to it. The approach flow thus observes an approximately 1-millimeter thick planar obstruction. The pressure difference and temperature are then recorded. The pressure difference is related to the approach velocity, and the angle determines the tangential and axial velocity components in this case. The local mass flux is then determined from the axial velocity component and the temperature (necessary to compute the flow density), and... 

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