Shear generated

Another well-known phenomenon is the Weissenberg effect, which occurs when a long vertical rod is rotated in a viscoelastic liquid. Again, the shearing generates a tension along the streamlines, which are circles centred on the axis of the rod. The only way in which the liquid can respond is to flow inwards and it therefore climbs up the rod until the hydrostatic head balances the force due to the normal stresses. 

A less gentle, but widely used, solubilization device is the common electric blender. This method may be used for plant or animal tissue, but it is not effective for disruption of bacterial cell walls. A blender that is more scientifically designed is the rotor stator homogenizer. The stator is a hollow tube and the rotor, attached to the stator, is a rapidly turning knife blade. Cells are torn apart by the turbulence and shear generated by the rotor. 

Operating feature Shear generation Pressure generation... 

These observations make it highly probable that similar reactions occur when carbon black is exposed to thermally or shear-generated polymer free radicals during processing of rubber compounds or to polymeric radicals formed during vulcanization, particularly in such typically free radical cross-linking systems as peroxide or radiation. 

The emulsion must be formulated to withstand the shear generated by mixing during the extraction but must be broken to remove the internal phase and reformulate the emulsion. This requires an additional process step and additional energy Inputs. Consequently, this process has limited potential applications to recovery of products with high added value or to pollution control, where process efficiency and degree of separation may be more Important than the cost of the process. 

Another recent application uses thermal FFF in the radial direction of a circular channel and fluid shear generated by rotating one wall relative to the other. Polymer mixtures were continuously fed into the channel near the centre, and different molecular weight fractions were removed from the channel at points around the outer circular edge. 

The shear generated by the impeller itself is not responsible for cell death. However, the smaller bubbles produced by the shearing action of the impeller can contribute significantly to ceU death. Experiments in unsparged baffled reactors in which oxygen was suppUed from headspace did not show any ceU damage. 

Melt rheology is illustrated with Aclryn . The combination of applied heat and shear-generated heat brings the melt to 320 to... 

In addition to identification of twin-screw extruders based on the direction of screw rotation, the distance between the two screws varies from fully intermeshing at one end of the spectrum to nonin-tenneshing with distance between the screws at the other extreme. Material flow and the shear generated depend on the degree of intermeshing [53,54]. Screw designs (Table 12.2) are defined as either open... 

C2 was injected at a greater injeetion velocity, which generates a diminution of fiber length with respect to Cl, (Fig. 4, Table 3). This is due to the shear generated during... 

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