In 1917 PA Kober published a paper in which he described his observation that 'a liquid in a collodion bag, which was suspended in the air, evaporated, although the bag was tightly closed'. Kober was not the first researcher to observe this phenomenon, but the first to realize its potential for the separation of liquid mixtures which otherwise are difficult to separate, and to separate them under moderate conditions. He introduced the terms 'Pervaporation', and 'Perstil-lation', and the first term is now in use to describe in

Figure 12 Microfiltration flux when filtering a particle suspension, with and without backflush.

(about 0.5 bar) for several seconds every few minutes (Figure 12).

Fouling is reduced by high cross-flow velocities and low transmembrane pressures. High cross-flow velocities cause high-pressure drops along the membrane, which cause the AP to be undesirably high at the entrance of the membrane module. Therefore microfiltration processes have been developed which facilitate a cross-flow both on the feed side and on the permeate side. The pressure drops on both sides are similar in magnitude, guaranteeing a uniform transmembrane pressure. This method of operation has been shown to be effective in many dairy applications.

Other process techniques to reduce fouling are the use of pulsed flow, gas sparging, and electric or acoustic fields, and the use of flow geometries that create secondary flows or vortices resulting in high shear rates (e.g. the use of 'turbulence promoters' or curved channels).

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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