Manometer effect

The second term is the manometer effect and accounts for the difference in solids densities in the bed outside the flapper valve and that inside the valve. If there is no difference in these densities, or if the dipleg is not submerged, this term vanishes. In lightly-loaded (that is, second or third-stage) cyclones for which Eq. (11.B.8) mainly applies, the dipleg solids density is normally less than that of the bed. This results in a positive contribution to the solids backup, h. We may note that the backup increases as the submergence increases and with a decrease in dipleg solids density. 

There are a number of relatively simple experiments with soap films that illustrate beautifully some of the implications of the Young-Laplace equation. Two of these have already been mentioned. Neglecting gravitational effects, a film stretched across a frame as in Fig. II-1 will be planar because the pressure is the same as both sides of the film. The experiment depicted in Fig. II-2 illustrates the relation between the pressure inside a spherical soap bubble and its radius of curvature by attaching a manometer, AP could be measured directly. 

Instruments for measuring the velocity as a pressure effectively convert this energy into pressure. The transducer used is the Pitot tuhe (Figure 27.3), which faces into the airstream and is connected to a manometer. The outer tuhe of a standard pitot tuhe has side... 

Tube Size for Manometers To avoid capillary error, tube diameter should be sufficiently large and the manometric fluids of such densities that the effect of capillarity is negligible in comparison with the gauge reading. The effect of capillarity is practically neghgible for tubes with inside diameters 12.7 mm (% in) or larger (see ASME PTC, op. cit., p. 15). Small diameters are generally permissible for U tubes because the capillary displacement in one leg tends to cancel that in the other. 

The float is effectively a two-dimensional manometer, and, like its open-ended counterpart, it measures the film pressure difference between the two sides of the float. This is another reason why it is imperative that no leakage occur past the float assembly Leakage would increase the pressure on the reference side of the float. For the same reason, the side of the float opposite the monolayer must be carefully checked for any possible source of contamination, not just misplaced surfactant. One way of doing this is to slide a barrier toward the float from that side to verify that no displacement of the float occurs. In all aspects of film pressure measurement, the torque must be measured with sufficient sensitivity to yield meaningful results. 

Early studies of pressure effects on gases were carried out in apparatus with glass components, which could not withstand pressures exceeding about 0.4 kbar. In order to extend T. Andrews studies of critical point behavior, French physicist E. H. Amagat (1841-1915) developed a glass-free hydraulic manometer that was able to achieve static pressures up to 3 kbar, the practical limit until about 1905. 

Valencia oil. see Citrus Orange Valine, hydrolysis, effect on, 134 Vapor pressure, 4. see Water activity Vapor pressure manometer (VPM), 61 -66 Vegetable oils characteristics of, 525 refined, tocopherol/tocotrienol... 

It s easy to demonstrate with manometers that a solution of a nonvolatile solute has a lower vapor pressure than the pure solvent (Figure 11.9). Alternatively, you can show the same effect by comparing the evaporation rate of pure solvent with the evaporation rate of a solution. A solution always evaporates more slowly than a pure solvent does, because its vapor pressure is lower and its molecules therefore escape less readily. 

An alternative is an arrangement of manometer and porous pot which effectively compares the rate of diffusion of a gas with that of air (Figure 16.1). This can be used to show that carbon dioxide diffuses slower than air and hydrogen diffuses faster. 

Cold traps must be used if mercury is used in your system (such as manometers, diffusion pumps, bubblers, or McLeod gauges) and if your mechanical pump has cast aluminum parts. Mercury will amalgamate with aluminum and destroy a pump. Even if your mechanical pump does not have aluminum parts, the mercury may form a reservoir in the bottom of the mechanical pump, which may cause a noticeable decrease in pumping speed and effectiveness. Aside from a cold trap between the McLeod gauge and the system, place a film of low vapor pressure oil in the McLeod gauge storage bulb. This oil will limit the amount of mercury vapor entering the system that makes its way to the mechanical pump. In addition, an oil layer should be placed on the mercury surface in bubblers and other mercury-filled components. 

The mechanics of a U-tube manometer are simple The difference between the levels of two interconnected columns of liquid is directly proportional to the difference between the pressures exerted upon them, assuming equal capillary effects on both tubes. 46 In practice, one end of a manometer is attached to an unknown pressure, and the other end is attached to a reference pressure that is known. For all practical purposes, the known value needs only to be a much smaller order of magnitude than the unknown value. 

Mercury Manometer. An open-end U-tube mercury manometer, known historically as the Torricelli barometer, can typically be read to 0.05 mmHg, but should be corrected for the capillary depression of mercury in glass and for residual gases in the "vacuum" above the column these two small effects are usually corrected for by the manufacturer s scale next to the column. The isoteniscope is just a fancy term for a U-tube of the Torricelli type, containing a liquid, which measures pressure differences by different heights of the liquid in the two arms, one open to the system under study, the other open to air. 

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