Rotating vane

Fig. 5. Operating sequence for a rotating-vane positive-displacement meter.

Rotating vanes are provided in the rooms to ensure diffuse sound fields. Sound is introduced into the source room, the average sound pressure level is measured in one-third octave bands in both rooms, and the sound-transmission loss is calculated as follows, where and die average sound... 

Gas velocihes can also be measured with anemometers (rotating vane, hot wire, etc.), from visual observations such as the velocity of smoke puffs, or from mass balance data (knowing the fuel consumption rate, air/ fuel ratio, and stack diameter). 

Vacuum pump (either liquid ring or rotating vanes type)... 

The central transport chamber is an 80-cm-diameter stainless steel vessel, and is pumped by a 1000-1/s turbomolecular pump, which is backed by a small (501/s) turbomolecular pump to increase the compression ratio for hydrogen, and by a 16-m /h rotating-vane pump. UHV is obtained after a bake-out at temperatures above 100°C (measured with thermocouples at the outside surface) of the whole system for about a week. A pressure in the low 10 " -mbar range is then obtained. With a residual gas analyzer (quadrupole mass spectrometer, QMS) the partial pressures of various gases can be measured. During use of the system, the pressure in the central chamber is in the low 10 -mbar range due to loading of samples. Water vapor then is the most abundant species in the chamber. 

A mechanical air separator is shown in Figures 1.35 and 1.36. The material is introduced at the top through the hollow shaft and falls on to the rotating disc which throws it outwards. Very large particles fall into the inner cone and the remainder are lifted by the air current produced by the rotating vanes above the disc. Because a rotary motion has been imparted to the air stream, the coarser particles are thrown to the walls of the inner cone and, together with the very large particles, are withdrawn from the bottom. The fine... 

The use of a rotating vane has become very popular as a simple to use technique that allows slip to be overcome (33,34). Alderman et al (35) used the vane method to determine the yield stress, yield strain and shear modulus of bentonite gels. In the latter work it is interesting to note that a typical toique/time plot exhibits a maximum torque (related to yield stress of the sample) after which the torque is observed to decrease with time. The fall in torque beyond the maximum point was described loosely as being a transition from a gel-like to a fluid-like behavior. However, it may also be caused by the development of a slip surface within the bulk material. Indeed, by the use of the marker line technique, Plucinski et al (15) found that in parallel plate fixtures and in slow steady shear motion, the onset of slip in mayonnaises coincided with the onset of decrease in torque (Fig. 8). These authors found slip to be present for... 

Solids Metering The control valves described earlier are primarily used for the control of fluid (liquid or gas) flow. Sometimes these valves, particularly the ball, butterfly, or sliding gate valves, are used to throttle dry or slurry solids. More often, special throttling mechanisms such as venturi ejectors, conveyers, knife-type gate valves, or rotating vane valves are used. The particular solids-metering valve hardware depends on the volume, density, particle shape, and coarseness of the solids to be handled. 

SPRAYS FROM ROTATING VANED ATOMIZER WHEELS ... 

Low pressures can be achieved in a mechanical or "roughing" pump, by using a fluid (water, mercury, oil) in a rotating-vane technique to adsorb molecules within the fluid when exposed to the container to be evacuated, then expelling these molecules to the laboratory when the vane has brought the fluid into contact with laboratory air. 

There are three main purposes of the oil. Lubrication and sealing are obvious, but the oil also is necessary to help provide the very high compression ratios required at low inlet pressures. At low inlet pressures the exhaust valve may not open because there is dead volume between the valve and the rotating vane. However, if there is oil in the compression/exhaust chamber the dead volume is reduced, sometimes eliminated, just before the gas reaches exhaust pressure. Continued movement of the piston then forces the oil and the small volume of gas through the exhaust valve. Too little oil and the compression ratio is not obtained, too much oil and the oil takes up space that would otherwise be gas. 

Figure 6-4. Cross section of a rotating vane vacuum pump and how it operates.

There are several direct methods of measurement of yield stress. The constant stress rheometer is most frequently used to determine value in shear. Dzuy and Boger [1983, 1985] used a rotational vane viscometer. Yield stresses in compression can be calculated from the unrelaxed stress values in parallel plate geometry. Its value in elongation has been directly measured as the critical stress value below which no sample deformation was observed during 30 minutes of straining in an extensional rheometer. 

FIGURE 5-7 Mechanical choppers lor modulating a light beam (a) rotating disk chopper, (b) rotating vane chopper. 

PUMP, ROTARY - A pump that moves fluid by positive displacement, using a system of rotating vanes, gears, or lobes. 

Vacuum systems with rotary vane vacuum pumps may be used where the process requires vacuums < 50 mbar or if liquid ring vacuum pumps cannot be used in the installation. These vacuum systems are designed to separate out as much of the process vapours and particles as possible on the intake side or to condense the process vapours into the atmosphere as moist air. Rotary vane vacuum pumps may be operated as recirculahng lubrication or blow-by vacuum pumps. The vacuum pump is built with a rotor turning eccentrically in a cylinder. The rotor has axial slots and rotating vanes are pressed against the cylinder by centrifugal force in these slots (Fig. 3). 

Current meters are hydrodynamic instruments with rotating vanes or buckets. The speed of their rotation is proportional to the flow velocity. The forerunners of current meters were the paddle wheels developed in the early 18 century. These were applied by Francesco Domenico Michelotti (1710-1777) in 1767, or by Pierre-Louis Du Buat (1734-1809) in 1786. There are two principal types of current meters, namely the screw and the cup types. The first was conceived by the famous British engineer Robert Hooke in 1783 to measure wind velocity with four vanes similar to a windmill. This type was developed by Reinhard Woltman (1757-1837) in 1790, Andre Baumgarten (1808-1859), Albert Ott (1847-1895), Alphonse Fteley (1837-1903) and Haskell, among many others. The other type meter has several cups on spokes rotating around an axis oriented transverse to the current. These anemometers were first applied around 1850 to measure wind velocities, and then were developed by Theodore Gunville Ellis (1829-1883), or William G. Price (1853-1928) to record flow velocity in rivers. 

Fig. 10.5 High-pressure attachment for the rheometer, consisting of a magnetic coupiing, a pressure head, a rotating vane geometry, and a cup. (Reprinted with permission from industriai and Engineering Chemistry Research, Voi. 42(25), N.M.B. Fiichy,...

Revolving extractor, countercurrent gravity percolation extractor, solvent-proof body with slowly rotating vanes (rotating individual extraction sections). The rotary-vane passes the continuously fed conditioned solids from the feed shaft over a fixed sieve tray in one rotation to the solids discharge shaft. Sieve tray slots are concentric and expanded at the bottom. At the same time solvent is trickled over the solids. Solvent percolates through the solids and the sieve tray and collected in underneath extract chambers. Countercurrent flow of solids and solvent. 

Rotating-vane sealed drum, lobed impeller meters... 

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