Cylindrical collectors

Fig. 2. Downs cell A, the steel shell, contains the fused bath B is the fire-brick lining C, four cylindrical graphite anodes project upward from the base of the cell, each surrounded by D, a diaphragm of iron gau2e, and E, a steel cathode. The four cathode cylinders are joined to form a single unit supported on cathode arms projecting through the cell walls and connected to F, the cathode bus bar. The diaphragms are suspended from G, the collector assembly, which is supported from steel beams spanning the cell top. For descriptions of H—M, see text.

On approaching a collecting body (fiber or liquid droplet), 0 porticle corried along by the gas stream tends to follow the stream but may strike the obstruction because of its inertia. Solid lines represent the fluid streamlines oround a body of diameter Dt, and the dotted lines represent the paths of particles that initially followed the fluid streamlines. X is the distance between the limiting streamlines A and B The fraction of particles initially present in a volume swept by the body that is removed by inertiol interception is represented by the quantity X/Dt, for a cylindrical collector and (X/Dt,) for a sphericol collector... 

The TID design proposed Patterson consists of an alkali metal doped cerwlc cylinder, containing an embedded heater surrounded by a cylindrical collector electrode [100]. The ceramic thermionic emitter is biased at a negative potential with respect to the collector electrode, and it is heated to a surface temperature of 400-800 C, depending on the mode of detection. The response of the detector to different elements depends on the electronic work function of the thermionic surface (i.e., the... 

Figure 3. Total ionization source of Tate and Lozier70 where F is the filament L the electron lens K a cylindrical gauze defining an equipotential electron path G discs E ion collection cylinder D electrometer guard cylinder C shield T electron collection cylinder and P electron collector.

Figure 29.4, illustrates a schematic diagram of a flame-ionization detector. It comprises of a positively charged ring (also referred to as cylindrical collector electrode), whereas the flame jet serves as the negative electrode. The flame jet has two inlets from the bottom of the column effluent is introduced and from the side H2 to form the fuel, whereas air is let in uniformly around the base of the jet. 

There are several types of wet collectors including spray towers, packed towers, and wet centrifugal collectors. The spray tower is a cylindrical or rectangular tower into which the incoming air is passed. Highspeed water sprays in the tower impact and remove the dust that is subsequently separated from the droplets by various types of eliminators. Spray towers are effective for all kinds of dust and even moisture-laden gases. 

It comprises an axially mounted W filament and three cylindrical collectors Ci,Ci, and Ci. All collectors are maintained at the same positive potential with respect to the W filament, but only the emission current collected from Ci is recorded. In the region of C2 the temperature and the surface concentration of adsorbate on the emitter are assumed to be uniform. 

Fig. 8. Cross section of the cylindrical condenser for measurements of the kinetic energies of the photoelectrons from gas molecules. 1—fluorescent layer for intensity measurements of the incident light 2—thick metallic cylinder with wrought semi-annular slits 3—Teflon insulator 4—cylindrical grid 5—electron collector 6—LiF window 7—diaphragm 8—shutter 9—exit slit of the vacuum monochromator.

The apparatus and procedures for studying the ionization related to catalytic combustion have been described (20). A potential of 300 volts d.c. was maintained between the cylindrical collector and the heated filament, with the collector being negative. After the filaments had been conditioned at 1000°C. for a few minutes, the background current was less than 0.01 X 10"9 amp., even at the highest filament temperatures used (900°C.). 

Impaction When an air stream containing particles flows around a cylindrical collector, the particle will follow the streamlines until they diverge around the collector. The particles because of their mass will have sufficient momentum to continue to move toward the cylinder and break through the streamlines, as shown in Figure 8.3. The collection efficiency by this inertial impaction mechanism is the function of the Stokes and the Reynolds number as ... 

Interception The inertial impaction model assumed particles had mass, and hence inertia, but no size. An interception mechanism is considered where the particle has size, but no mass, and so they can follow the streamlines of the air around the collector. If a streamline which they are following passes close enough to the surface of the fiber, the particles will contact the fiber and be removed (Figure 8.4). The interception efficiency depends on the ratio of the particle diameter to the cylindrical collector diameter (k= dp/Dc) ... 

Effect of Multiple Layers and Packing All correlations for the collection efficiency discussed so far are based on the ideal case of a single cylindrical collector. Now, let s examine a filter unit consisting of randomly oriented multiple layers. Consider an area (A) of filter at a right angle to the gas flow and with a depth dh. If the packing density a is defined as the volume of fiber per unit volume of filter bed, the velocity within the filter void space is equal to... 

Based on the combined mechanisms of impaction, interception, and diffusion, a minimum efficiency should result for spheres depositing on cylindrical collectors. 

Due to the radial symmetry of the three configurations, a 2D model is employed. Figure 4.20 depicts the geometry considered for case 1, i.e. current collectors at the tube ends (not in scale). In cases 2, an additional 16 pieces of conductive material (nickel), with a square section of 1.5 x 1.5 mm, are considered on the cathode (external surface of the tube). In case 3 the conductive materials are present both inside and outside the tube. It should be noted that in case 2 and 3, cylindrical symmetry is not obvious anymore. However, it is reasonable to assume that voltage losses are mainly proportional to ohmic in-plane losses, i.e. to the length of the current path along the tube. In case 2 and 3, this distance is constant in each longitudinal tube cross-section, therefore a cylindrical symmetry is assumed. 

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