Pressure height difference

The standpipe s height provides the driving force for transferring the catalyst from the regenerator to the reactor. The elevation difference between the standpipe entrance and the slide valve is the source of this pressure buildup. For example, if the height difference is 30 feet (9.2 meters) and the catalyst density is 40 Ib/ft (641 kg/m ), the pressure buildup is ... 

Self-Test 4.2B What is the pressure in millimeters of mercury inside a system when a closed mercury manometer shows a height difference of 10. cm at 15°C ... 

A student attaches a glass bulb containing neon gas to an open-tube manometer (refer to Fig. 4.5) and calculates the pressure of the gas to be 0.890 atm. (a) If the atmospheric pressure is 762 Torr, what height difference between the two sides of the mercury in the manometer did the student find ... 

The washing of capillaries with dilute alkaline solution is advisable before analysis. The alkaline solution can be followed by deionized water and buffer. Capillaries can be washed between runs too. Samples can be introduced into the capillary by hydrodynamic and electro-kinetic methods. The hydrodynamic method applies a pressure difference (5-10 sec) between the two ends of the capillary. The pressure difference can be achieved by overpressure, vacuum or by creating a height difference between the levels of the buffer and sample reservoirs. In the case of electrokinetic injection, the injection end of the capillary is dipped into the sample for a few seconds and a voltage of some thousand volts is applied. 

From an instrument perspective, the simplest hydraulic approach to transport focused zones to the detector is by gravity mobilization.79 In this technique, focused proteins are transported toward the detection point using a difference in the levels of anolyte and catholyte contained in the reservoirs. The force generated by the liquid-height difference can be manipulated to be extremely small compared with pressure or vacuum. Flow velocity can also be modulated by changing the capillary dimensions or, in the case of large-bore capillaries, with internal diameters greater than 50 pm, by the addition of viscous polymers. 

Equation (5) is sometimes called a barometric height relation. For an isothermal atmosphere, a measurement of the temperature T and the static pressure (as with a barometer) at two different levels will provide data for (he calculation of the height difference. 

Notice that one end of the U-tube is connected to the smaller diameter section of the Venturi tube, whereas the other end is connected to one of the larger diameter sections. If the fluid is flowing from left to right, according to the Bernoulli equation, v2 > vl and P2 < Pr The fact that the pressure is lower in the narrow part of the tube is the primary scientific basis for the operation of an aspirator. The fluid levels in the manometer will reflect the pressure difference between Pt and Pr A measure of the height difference Ah and a knowledge of the density of the fluid in the manometer will yield the pressure difference between Pj and P2 using ... 

This hydraulic jack lifitng process is done at constant speed. If the two pistons are at different levels, as they usually are in real jacks used for lifting, there s a pressure difference between the two pistons due to height difference (rho)gh. In textbook examples this is generally considered small enough to neglect and may not even be mentioned. 

FIGURE 9.3 (a) Boyle s J-tube. When the heights of mercury on the two sides of the tube are the same, the pressure of the confined gas must equal that of the atmosphere, 1 atm or 760 mm Hg. (b) After mercury has been added, the pressure of the gas Is Increased by the number of millimeters of mercury In the height difference h. The compression of the gas causes It to occupy a smaller volume. 

Osmotic pressure is particularly useful for measuring molar masses of large molecules such as proteins, whose solubilities may be low. In the case given in Example 11.16, the height difference h is 22 cm, an easily measured quantity. By... 

U-shaped tube filled with liquid connected to an experimental system -> open-tube pressure (system) = atmospheric pressure when levels are equal closed-tube pressure (system) = difference in level heights... 

As an acoustic wave propagates it is attenuated by absorption in the medium. This process results in a radiation pressure which is proportional to the absorbed energy and acoustic streaming (vide supra). The pressure can be measured from the height difference of liquids in two connected tubes, one being sonicated and the other not, at different values of z where z is the distance from the emitter surface. If we let I2 be the sound intensity at z and Io the sound intensity at the surface of the emitter then,... 

When the solid phase is fixed (e.g., as a capillary, membrane, or porous plug), an electric field induces a flow of liquid termed electro-osmosis. The character of the flow depends on the construction of the apparatus. For example, in an electrophoretic cell, the liquid flows in one direction near the walls and in the opposite direction in the center of the cell, and the net flow across the cell cross-section is zero (Figure 2.2). Electro-osmosis can also be demonstrated as a difference in pressure (height of a water column) generated as a result of an electric field applied to a capillary, membrane, or porous plug. 

A U-tube manometer, shown in Figure 6-8, is quite easy to operate. The pressure is measured in the open tube type by measuring the differences in height between the two columns of Hg. In this case, the height difference increases as the pressure decreases. The closed end type requires that the Hg be boiled under reduced pressure until the dissolved gases are removed before you fill the tube. If this is not done, then an air bubble eventually forms at the top of the sealed end and ruins the measurements. In this type, the differences in mercury height decreases with a decrease in pressure. This type of manometer can be used to measure pressures from atmospheric down to about 1 to 2 torr (0.13 - 0.26 kPa), but the accuracy decreases below 5 to 10 torr (0.67-1.3 kPa). 

We will assume that the network is carrying liquid at constant temperature, so that the specific volume is the same all along the pipe. To retain p, zi, V and P2,zi as the boundary conditions, the pressures and heights downstream of each conductance have been labelled Pm.i,Zmj ( m for midway). We may expand the pressure and height differences between pipe inlet and outlet as follows ... 

Similarly, applying the model of Chapter 4, Section 4.11, with height differences neglected, the line pressure drop is related to flow by ... 

Constant-mass reactor. The constant-massreactoTTanbe achieved if a differential pressure measurement is used to control the. flow-rate out of the reactor and the reactor has constant cross-sectional area. The difference in pressure between the top and bottom of the reactor is determined by ph in which h is the height difference. If the cross-sectional area is independent of height, then the pressure difference is also proportional to pVn, the total mass in the reactor. So if the flow controller maintains constant pressure difference, it also maintains constant mass. In this situation pVr is specified as the additional equation. 

The pressure head includes the pressure difference between the supply and storage points, the pressure due to height difference, as well as the pressure drop due to friction ... 

As shown in Figure Q4.13, a U-tube manometer measures the pressure drop of water in a pipe. If the height difference in the two legs of the manometer filled with mercury is 15.2 cm, what is the pressure difference between points A and B1... 

Partial or complete permeation of the solute can frequently be recognized when measurements are made from below (capillary height difference A/ o at / = 0 smaller than II) since the observable pressure A/ goes through a maximum before reaching the equilibrium value (Figure 9-3). The effect is the... 

Plan We will use the difference in height between the two arms (h in Figure 10.3) to obtain the amount by which the pressure of the gas exceeds atmospheric pressure. Because an open-end mercury manometer is used, the height difference directly measures the pressure difference in mm Hg or torr between the gas and the atmosphere. 

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