Cylindrical rotating cylinder

Centrifugal extrusion encapsulation, or coaxial extrusion processing, is a liquid coextrusion process that uses an assembly of cylindrical nozzles consisting of concentric orifices located at the outer circumference of a rotating cylinder (Figure 24.3). 

Fig. 13. Succession of two-dimensional VEXSY images for cylindrical Couette flow where corresponds to (a) 0.15, (b) 0.50, (c) LOO, and (d) 2.00 rotation cycles for the central rotating cylinder. The theoretical image is shown on the left with the corresponding experimental data on the right. The full width of the image corresponds to 33 cm s . [Reproduced by permission from Callaghan and Manz, 1993.]...

Figure 11.12 Schematic representation of a rotating cylinder electrode a) entire cylinder used as working electrode. This geometry provides a uniform current and potential distribution at and below the mass-transfer-limited current, b) band-shape cylindrical coupon used as a working electrode. This geometry is useful for studies conducted at the open-circuit condition.

Cubers and pelletizers consist of a cylindrical die from hard steel, perforated with holes. Inside the die there are two rollers mounted on the periphery of the die. There are two designs of the machine as regards the rotating part. In one design, the die rotates while the rollers do not, and vice versa in the second. In another design of the machine, rollers have been replaced by an eccentrically rotating cylinder. 

Flow at a rotating cylinder in a large cylindrical cell with baffles v) = rotation d = rotor diameter d0 = cell diameter h = (djdyi Re = vjdh/2v Sh = kdJD Sh = 1.83Re° 58Sc 3... 

The most comprehensive fatigue wear model (2) proposed In the literature was used to predict wear rates to within 30 percent or less of the experimentally measured values (J). The exponent t was determined from notched cylindrical specimens In reverse bending. The number of contacts and the areas were determined from surface profiles of the polymer and the counterface after steady-state wear was attained. The wear data was obtained from a polymer pin sliding on a rotating cylinder. 

The Landolt cell (Figure 5.27) provides controlled convection conditions by the rotating cylinder electrode. A cylindrical shield surrounds a rotating cylinder, preventing direct current flux between rotating cylinder and counter electrode. The enforced longer way of the current lines simulates the variation of current density in a conventional Hull cell. 

Similar cells based on cylindrical geometry have been proposed. In the stationary version, the electrolyte is pumped through a thin gap between two electrodes formed by the inside of a pipe and a concentric central cylinder. When the central electrode is rotated the cell is again self-pumping and the rotating cylinder cell has many of the attractions of the pump cell. It has been manufactured commercially for the removal of metal ions from dilute solutions. The cylinder cells have a poor space time yield compared with their disc counterparts but have the advantage that they may be modified to include a separator. 

By the abovementioned way of measuring the viscosity, that is, sliding plate, the absolute or otherwise known as dynamic viscosity (q or q) is measured. At this point, it should be mentioned that the relative movement of the two solid surfaces could also be rotary such as in a system of cylindrical container and rotating cylinder, or of a flat surface (plate) with a rotating cone, or of a flat surface (plate) with a rotationally oscillating circular plate. All these systems are basically the different types of viscosity measuring devices that measure dynamic or absolute viscosity (dynamic viscometers). 

Continuous filtration is discussed by Coulson and Richardson.. It commonly employs rotary vacuum filters. These are usually cylindrical in shape, rotating about a horizontal axis with a filter medium on the curved surface and a vacuum applied from inside. Rotating disc filters are less frequently employed (see Fig. 2.4). These have a number of discs on the same shaft with vacuum applied from inside but the flat surfaces of the discs hold the filter medium. The methods of continuous discharge of the filter cake during operation, and of replacement of the filter medium at intervals, are less elegant than those applicable to rotating cylinders. 

A rotating cylinder electrode (RCE) with a cylindrical or pseudo-cylindrical counterelectrode around it essentially has the geometry of a parallel plate cell. The RCE was developed as a specialty tool for uniform fast electrodeposition in turbulent flow, and for the removal of metal ions from effluents with recovery of the metal in the form of a foil, flake, or powder [61-63]. In the first application, RCE cathodes became the major tool for silver removal from photographic fixer solutions in compact, high-rate units [64], and enabled the recycling of fixer and resale of more than 98 wt% of the silver. Typically, such cells had a stainless steel RCE cathodes of 10-20 cm diameter rotating at speeds up to 1400 rpm, stationary graphite anodes, and were operated at 50 A. 

Considerable published work is available on the subject of superlaminar flow between rotating cylinders but little frictional loss data is available, and then not at Reynolds numbers greater than 10 5. Furthermore the published work is limited to either plain circular cylinders or to discs, and there is no data available for more complex shapes incorporating both cylindrical surface and radial disc elements such as make up the majority of turbomachinery components. 

Other hydrodynamic cases for corrosion studies can be found elsewhere [10]. On the other hand, for a continuous metal removal from solution in electrowinning, rotating cylinders and disks are used as cathodes (Figme 7.6). The classical rotating-disk cathode is known as Weber s disk [25-26] having a diameter of 2a. The corresponding differential equation in cylindrical coordinates is free of the diffusivity and it is given by... 

The viscosity can be obtained from formula (12-12) by measuring Tas a function of Q. The measurement by the rotating cylinder viscometer provides the flow curve, cr s.y. The shear stress, a, acting on the cylindrical layer located at a distance r from the central axis is expressed by the formula ... 

One production line of a paper mill consists according the size and the quality of the produced paper sometimes from more than 50 steam drums to dry and flatten the produced paper. These drums (cylinders with flat bottoms, see figure 1) will be used with a steam pressure up to 500 kPa (5 bar) and additionally with a rotation speed up 1200 m.min the material is mainly grey cast iron (with lamellar graphite). The diameters can reach up to 2.2 m and the cylindrical lengths up to 10 m. For the specific flattening drums the cyhndrical diameters can be up to 5 m and more. 

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