Counterrotating

Roll Crushers. Traditional roU emshers effect size reduction by cmshing single particles between two counterrotating roUs hence they are emshed between the two surfaces. The roUs can either be smooth or profiled to aid feeding of coarser materials. Figure 6 shows a particle of diameter x being reduced between two roUs of diameter D. For smooth roUs D/x > 17 is usually selected, whereas for profiled roUs this can be varied to D/x < 10. The feed size-to-gap width ratio is essentially limited to approximately 4. 

Counterrotating intermesning screws provide a dispersive milling action between the screws and behave like a positive displacement device with the ability to generate pressure more efficiently than any other extruder. 

FIG. 19-46 Magnetic-field distribution charts, a) Concurrent and counter-current wet drum magnetic separator, 1.2-m diameter, (h) Counterrotation wet drum magnetic separator, 1.2-m diameter. (Coutiesy of Sala International, Inc.)... 

The typical rotary screw compressor stage is made up of two rotating shafts, or screws. One is a female rotor and the other a male rotor. These two rotating components turn counter to one another (counterrotating). The two rotating elements are designed so that as they rotate opposite to one another their respective helix forms intermesh (see Figure 3-78). As with all rotary compressors, there are no valves. The gas is sucked into the inlet post and is squeezed between the male and female... 

Corotational flows distribute material better than counterrotational flows. 

Screw compressors use two counterrotating screw-like shafts (Figure 13.11a). Lubricating oil is required in some designs to lubricate the rotors, seal the gaps... 

Rotary piston or rotary lobe or roots compressors use two counterrotating matching lobe-shaped rotors (Figure 13.11b). Each revolution of the lobes delivers four pulses of gas. Maximum discharge pressures in a single stage are up to 2.5 bar. Suction flowrates of up to 3 m3s 1 are possible. 

Fig. 1. Process flow sheet for the continuous conversion of latex in a counterrotating, tangential twin-screw extruder as it might be arranged for the production of acrylonitrile-butadiene-styrene polymer (Nichols and Kheradi, 1982). Polystyrene (or styrene-acrylonitrile) melt is fed upstream of the reactor zone where the coagulation reaction takes place. Washing (countercurrent liquid-liquid extraction) and solids separation are conducted in zones immediately downstream of the reactor zone. The remainii zones are reserved for devolatilization and pumping.

Fig. 10. Schematic representation of nonintermeshing counterrotating twin-screw extruder.

Films and sheets are made from precipitation and/or regeneration of a polymer solution or melt. Calendering is also used where the polymer is passed between a series of counterrotating rollers. 

Figure 7.62 Schematic diagram of (a) corotating and (b) counterrotating twin screws. Reprinted, by permission, from A. B. Strong, Plastics Materials and Processing, 2nd ed., p. 365. Copyright 2000 by Prentice-Hall, Inc.

Type Single Screw Corotating Screw Low-Speed High-Speed Type Type Counterrotating Twin Screw... 

More recent experiments [62] concerning the viscous sublayer have shown a three-dimensional structure for turbulence near the wall. In a plane normal to the mean flow, counterrotating eddy pairs are involved (Fig. 6c), whereas in the direction of the mean flow, the motion is quasi-periodic (as described earlier). Since the wavelength along the mean flow is much larger than along the perimeter of the tube, a simplified bidimensional model may account only... 

It is still possible to have the Sagnac effect. If we consider the counterrotating portion of the non-Abelian contribution to... 

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