Annular orifice

Venturi scmbbers can be operated at 2.5 kPa (19 mm Hg) to coUect many particles coarser than 1 p.m efficiently. Smaller particles often require a pressure drop of 7.5—10 kPa (56—75 mm Hg). When most of the particulates are smaller than 0.5 p.m and are hydrophobic, venturis have been operated at pressure drops from 25 to 32.5 kPa (187—244 mm Hg). Water injection rate is typicaUy 0.67—1.4 m of Hquid per 1000 m of gas, although rates as high as 2.7 are used. Increasing water rates improves coUection efficiency. Many venturis contain louvers to vary throat cross section and pressure drop with changes in system gas flow. Venturi scmbbers can be made in various shapes with reasonably similar characteristics. Any device that causes contact of Hquid and gas at high velocity and pressure drop across an accelerating orifice wiU act much like a venturi scmbber. A flooded-disk scmbber in which the annular orifice created by the disc is equivalent to a venturi throat has been described (296). An irrigated packed fiber bed with performance similar to a... 

Labyrinth Seals The labyrinth is one of the simplest of the many sealing devices. It consists of a series of circumferential strips of met extending from the shaft or from the bore of the shaft housing to form a cascade of annular orifices. Labyrinth seal leakage is greater than that of clearance bushings, contact seals, or filmriding se s. 

Figure 10-19. Baffles with annular orifices. (Used by permission B.G.A. Skrotzki, B.G.A. Power, June 1954, by McGraw-Hill, Inc. All rights reserved.)...

Externally pressurized gas journal bearings have the same principle of operation as hydrostatic liquid-lubricated bearings. Any clear gas can be used, but many of the design charts are based on air. There are three forms of external flow restrictors in use with these bearings pocketed (simple) orifice, unpocketed (annular) orifice, and slot. 

Diffraction of detonation from a tube (0=52 mm) to half-space through an annular orifice with central conical obstacle ( = 15°) in a C2H2 + 2.5O2 mixture at 33 mbar initial pressure. Comparison of experimental soot patterns with numerical simulations. (Courtesy of B. A. Khasainov.)... 

Some of the hydrothermal emissions occur as focused and very hot discharges emitted through the annular orifices of rock chimneys that are tens of meters in height. The... 

Annular orifices can also be used to advantage for gas metering when there is a possibility of entrained liquids or solids and for liquid metering with entrained gas present in small concentrations. Coefficient K was found by Bell and Bergelin [Trans. Am. Soc. Mech. Eng., 79, 593-601 (1957)] to range from about 0.63 to 0.67 for annulus Reynolds numbers in the range of 100 to 20,000 respectively for values of 2L/(D — d) less than 1 where L = thickness of orifice at outer edge, D = inside pipe diameter, and d = diameter of orifice disk. The annulus Reynolds number is defined as... 

Figure 2.7 shows a typical pneumatic nebulization system for a premixed flame. The sample is sucked up a plastic capillary tube. In the type of concentric nebulizer illustrated here, the sample liquid is surrounded by the oxidant gas as it emerges from the capillary. The high velocity of this gas, as it issues from the tiny annular orifice, creates a pressure drop which sucks up, draws out and shatters the liquid into very tiny droplets. This phenomenon is known as the venturi effect and is illustrated in Fig. 2.8. 

The orifice-type flow measurement has been modified, and new, special-purpose devices have been introduced to meet particular process requirements. One such unique design is the annular orifice used to measure the hot and dirty gases in the steel industry. Here, the process flow passes through an annular opening between the pipe and a disk-shaped, concentrically located plate the pressure difference is detected between the upstream and downstream faces of that disk. (Refer to Table 3.81 for recommendations on selecting the right orifice plate design for various applications.)... 

The third method is also a continuous machine method, and, except that the molten glass flows vertically through an annular orifice instead of on to a rotating mandrel, it is similar to the second method. (Fig. 1.3.)... 

The B-type series of reactors were of similar construction except that a central wire electrode of stainless steel was used and the absorbent liquid was fed into the incoming gas as a spray. Dispersion of the liquid was achieved ultrasonically using a vibratory generator. The spray was fed into the gas stream through an annular orifice placed at a sufficient distance upstream from the discharge to ensure proper dispersal of spray in the electrode gap. The C-type reactor employed a pair of rectangular... 

The spinning of asymmetric hollow fibers with the skin on the inside closely resembles the procedure used in casting flat-sheet membranes. Figure 3.1510 is a schematic diagram of a spinneret used to spin these fibers. The degassed and filtered polymer solution is forced under pressure into a coaxial tube spinneret. The liquid is extruded through an annular orifice and the hollow fiber (still liquid) is stabilized and precipitated by an internal coagulating fluid (usually water) which flows out the center tube. 

The velocity of the spinning solution through the annular orifice of the spinneret. 

Pipes and hoses require an annular orifice. After leaving the die, while still hot and malleable, the pipe/hose is fed into a calibrator (which is a cylinder with an inner diameter identical to the required pipe/hose outside diameter) in which, either by internal pressure or by vacuum suction, the pipe/hose is pressed against the highly polished inside surface of the calibrator. 

Veilo Process. A method for the production of glass tubing molten glass flows vertically through an annular orifice the central refractory pipe within the orifice is hollow and rotates. The process will produce up to 1 tonne/h of tubing, 1.5-75mm dia. cf. danner... 

Write the criterion which makes it possible to ensure that the large particles come out through the annular orifice at the bottom of the apparatus. 

---