Liquid column measurements

A mass-based tank-gauging system quantify assessment based on hydrostatic pressure of the liquid column measurement. 

Since capillary tubing is involved in osmotic experiments, there are several points pertaining to this feature that should be noted. First, tubes that are carefully matched in diameter should be used so that no correction for surface tension effects need be considered. Next it should be appreciated that an equilibrium osmotic pressure can develop in a capillary tube with a minimum flow of solvent, and therefore the measured value of II applies to the solution as prepared. The pressure, of course, is independent of the cross-sectional area of the liquid column, but if too much solvent transfer were involved, then the effects of dilution would also have to be considered. Now let us examine the practical units that are used to express the concentration of solutions in these experiments. 

Pressure defined as force per unit area is usually expressed in terms of familiar units of weight-force and area or the height of a column of hq-uid that produces a like pressure at its base. Process pressuremeasuring devices may be divided into three groups (1) those that are based on the measurement of the height of a liquid column, (2) those that are based on the measurement of the distortion of an elastic pressure chamber, and (3) electrical sensing devices. 

Liquid Column Density may be determined by measuring the gauge pressure at the base of a fixed-height hquid column open to the atmosphere. If the process system is closed, then a differential pressure measurement is made between the bottom of the fixed height liquid column and the vapor over the column. If vapor space is not always present, the differential-pressure measurement is made between the bottom and top of a fixed-height column with the top measurement being made at a point below the liquid surface. 

Several micromanometers, based on the liquid-column principle and possessing extreme precision and sensitivity, have been developed for measuring minute gas-pressure differences and for cahbrating low-range gauges. Some of these micromanometers are available commercially. These micromanometers are free from errors due to capillarity and, aside from checking the micrometer scale, require no cahbration. See Doolittle, op. cit., p. 21. 

If the mobile phase is a liquid, and can be considered incompressible, then the volume of the mobile phase eluted from the column, between the injection and the peak maximum, can be easily obtained from the product of the flow rate and the retention time. For more precise measurements, the volume of eluent can be directly measured volumetrically by means of a burette or other suitable volume measuring vessel that is placed at the end of the column. If the mobile phase is compressible, however, the volume of mobile phase that passes through the column, measured at the exit, will no longer represent the true retention volume, as the volume flow will increase continuously along the column as the pressure falls. This problem was solved by James and Martin [3], who derived a correction factor that allowed the actual retention volume to be calculated from the retention volume measured at the column outlet at atmospheric pressure, and a function of the inlet/outlet pressure ratio. This correction factor can be derived as follows. 

The moving-drop method [2] employs a column of one liquid phase through which drops of a second liquid either rise or fall. The drops are produced at a nozzle situated at one end of the column and collected at the other end. The contact time and size of the drop are measurable. Three regimes of mass transport need to be considered drop formation, free rise (or fall) and drop coalescence. The solution in the liquid column phase or drop phase (after contact) may be analyzed to determine the total mass transferred, which may be related to the interfacial reaction only after mass transfer rates have been determined. 

The temperature difference between inlet and outlet temperature at the coil(s) of the refrigerant should be smaller than 1 °C (AT < 1 °C), to ensure a uniform condensation on the total coil. On warmer areas no ice will condense until the temperature at the ice surface has increased to the warmer temperature on the coil. For large surfaces it is necessary to use several coils or plates in parallel, each of which must be separately temperature controlled. If the condenser is operated in an overflow mode, the weight of the liquid column should not change the boiling temperature of the liquid at the bottom of the column measurably. 

The effect of nanoporous Ti02 thin-film electrodes on the removal and degradation of the reactive textile dye Reactive orange 16 (R3R) was investigated by physicochemical analytical procedures including RP-HPLC. The chemical structure of the dye is shown in Fig. 3.67. Liquid chromatographic measurements were employed for the separation and detection of the decomposition products of the dye. They were realized in an ODS column... 

In any study on bubble formation, the measurement of bubble volume is of primary importance. The bubbles formed at a nozzle ascend through the liquid column and rupture at the surface of the liquid. During their ascent,... 

It can be used for measuring bubble sizes not only at the nozzle tip but also at any position in the liquid column. Thus, even coalesced and ruptured bubbles can be examined by this method. 

Now, from its essential notion, we have the feedback interconnection implies that a portion of the information from a given system returns back into the system. In this chapter, two processes are discussed in context of the feedback interconnection. The former is a typical feedback control systems, and consists in a bioreactor for waste water treatment. The bioreactor is controlled by robust asymptotic approach [33], [34]. The first study case in this chapter is focused in the bioreactor temperature. A heat exchanger is interconnected with the bioreactor in order to lead temperature into the digester around a constant value for avoiding stress in bacteria. The latter process is a fluid mechanics one, and has feedforward control structure. The process was constructed to study kinetics and dynamics of the gas-liquid flow in vertical column. In this second system, the interconnection is related to recycling liquid flow. The experiment comprises several superficial gas velocity. Thus, the control acting on the gas-liquid column can be seen as an open-loop system where the control variable is the velocity of the gas entering into the column. There is no measurements of the gas velocity to compute a fluid dynamics... 

A set of experiments on gas-liquid motion in a vertical column has been carried out to study its d3mamical behavior. Fluctuations volume fraction of the fluid were indirectly measured as time series. Similar techniques that previous section were used to study the system. Time-delay coordinates were used to reconstruct the underl3ung attractor. The characterization of such attractor was carried out via Lyapunov exponents, Poincare map and spectral analysis. The d3mamical behavior of gas-liquid bubbling flow was interpreted in terms of the interactions between bubbles. An important difference between this study case and former is that gas-liquid column is controlled in open-loop by manipulating the superficial velocity. The gas-liquid has been traditionally studied in the chaos (turbulence) context [24]. 

Multiplying Gauges To attain the requisite precision in measurement of small pressure differences by liquid-column manometers,... 

On working flowsheets the detectors, transmitters, and controllers are identified individually by appropriate letters and serial numbers in circles. Control valves are identified by the letters CV- followed by a serial number. When the intent is to show only in general the kind of control system, no special symbol is used for detectors, but simply a point of contact of the signal line with the equipment or process line. Transmitters are devices that convert the measured variable into air pressure for pneumatic controllers or units appropriate for electrical controllers. Temperature, for instance, may be detected with thermocouples or electrical resistance or height of a liquid column or radiant flux, etc., but the controller can accept only pneumatic or electrical signals depending on its type. When the nature of the transmitter is clear, it may be represented by an encircled cross or left out entirely. For clarity, the flowsheet can include only the most essential information. In an actual design... 

MCLEOD GAGE. A liquid-level vacuum gage in which a known volume of gas. at the pressure to he measured, is compressed by the movement of a liquid column to a much smaller known volume. a> which the resulting higher pressure is measured,... 

The Coulter Counter contains a capillary through which a suspension is pumped. The electrical resistance of the liquid column is measured and depends on the resistance of the liquid medium, the resistance of the solid phase and the proportion of solid material in the suspension. From the size of the change in electrical resistance, certain conclusion can be drawn about the dimension of the particles in a certain fraction. 

Here, rc is the inner radius of the capillary, h is the height of the liquid column, and p is the density of the liquid. We assume that the liquid wets the inner surface of the capillary. The pressure inside the liquid can be varied by changing Pg with a pump. To measure the thickness of the film (or the distance between the two liquid-gas interfaces) white light is focussed from a normal direction onto the film. The light is reflected from both sides of the film and it interferes. The intensity of the reflected light is measured. From the interference the thickness can be calculated. 

Both the liquid and gas products were analyzed by gas chromatography. The column for the liquid analysis was 20% Apiezon L on 60-80 mesh Chromosorb P. The column measured 1/4 inch by 7 feet. The gas analysis utilized a 1/4 inch by 10 foot column of 60-80 mesh Chromosorb 102. Temperature programming was required in both analyses. Identification of the GC peaks was based on retention time of pure compounds when these were available. In addition, two of the samples were analyzed by combined gas chromatography-mass spectrometry. By comparing the observed mass spectrometer fragmentation patterns with tabulated patterns it was possible to identify virtually every component in the product. Further details are available in the theses by Wu (23) and Early (J+). 

Liquid-Column Methods Liquid-column pressure-measuring devices are those in which the pressure being measured is balanced against the pressure exerted by a column of liquid. If the density of the liquid is known, the height of the liquid column is a measure of the pressure. Most forms of liquid-column pressure-measuring devices are commonly called manometers. When the height of the liquid is... 

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