Differential pressure technique

Several techniques are available for measuring values of interaction second virial coefficients. The primary methods are reduction of mixture virial coefficients determined from PpT data reduction of vapor-liquid equilibrium data the differential pressure technique of Knobler et al.(1959) the Bumett-isochoric method of Hall and Eubank (1973) and reduction of gas chromatography data as originally proposed by Desty et al.(1962). The latter procedure is by far the most rapid, although it is probably the least accurate. 

Upon shutting in the well, the pressure builds up both on the drillpipe and casing sides. The rate of pressure buildup and time required for stabilization depend upon formation fluid type, formation properties, initial differential pressure and drilling fluid properties. In Ref. [143] technique is provided for determining the shut-in pressures if the drillpipe pressure is recorded as a function of time. Here we assume that after a relatively short time the conditions are stabilized. At this time we record the shut-in drillpipe pressure (SIDPP) and the shut-in casing pressure (SICP). A small difference between their pressures indicates liquid kick (oil, saltwater) while a large difference is evidence of gas influx. This is true for the same kick size (pit gain). 

A differential vapour-pressure technique has been used to determine the molecular weights of phosphonic and phosphinic acids in 95% ethanol. Cryoscopic and n.m.r. studies have been made on solutions of phosphinic acids in sulphuric acid and oleum. Mass spectrometry has indicated the ready formation of phosphinylium ions after electron bombardment of phosphonic and phosphinic acids and their derivatives. However, the cryoscopic results in sulphuric acid indicated that reaction did not proceed beyond protonation, and the n.m.r. study on oleum solutions suggested that sulphonation occurred. 

Results from constant differential pressure filtration tests have been analyzed according to traditional filtration science techniques with some modifications to account for the cross-flow filter arrangement.11 Resistivity of the filter medium may vary over time due to the infiltration of the ultrafine catalyst particles within the media matrix. Flow resistance through the filter cake can be measured and correlated to changes in the activation procedure and to the chemical and physical properties of the catalyst particles. The clean medium permeability must be determined before the slurries are filtered. The general filtration equation or the Darcy equation for the clean medium is defined as... 

The state of aggregation of RLi in various solvents has been investigated by a variety of methods. In 1967, West and Waack used a differential vapor pressure technique to study solution colligative properties of RLi . Deviations from ideality indicated that in THF at 25 °C, MeLi and BuLi are tetrameric, PhLi dimeric and benzyllithium monomeric. MeLi was also suggested to be tetrameric in diethyl ether. 

The value for [BMIM][PF6] corresponds to about 5700 bar, which is consistent with our measurements. However, it should be noted that Berger et al. [16] used a constant volume stoichiometric technique with a 50 cm vessel, pressurized to 50 atm. and containing 10 cm of IL. The resulting pressure drop when the gas is absorbed into the liquid would only be on the order of 0.005 atm. The authors do not report the uncertainty of their Henry s constants, nor the accuracy of their pressure gauge. Unless a highly accurate differential pressure transducer was employed, it is Hkely that these values are good order of magnitude estimates only. 

Concentric-orifice devices can be easily installed in high-pressure lenses. The high-end- and the low-end connection of such devices could be coupled with differential pressure transmitters, for example, with the before-mentioned devices of [54]. The devices are mounted in different ways. Mostly, the open pipe technique is used. Furthermore, both connected sides of the transmitter are fed with an inert gas, for example, nitrogen. For cases where the systems must separated, membrane devices can be arranged between them. All the mentioned orifice devices are technically proved and are applied in the high-pressure area. 

A further very simple method for level-measurement is a technique of feeding an inert gas or fluid into the upper and lower pipes of the measuring system which is connected with an apparatus. The differential pressure is a measure of the height of a fluid in an apparatus, for example a settler, or the level in a reactor of a chemical plant. 

Two other types of mechanical flow meters which can be used are the area flow and displacement meters. In addition, there exists much more sophisticated techniques for measurement offlow rate than use of differential pressure devices, such as anemometry, magnetic, and ultrasonic. 

Measurements of liquid density are closely related to quantity and liquid-level measurements since both are often required simultaneously to establish the mass contents of a tank, and the same physical principle may often be used for either measurement, since liquid-level detectors sense the steep density gradient at the liquid-vapor interface. Thus, the methods of density determination include the following techniques direct weighing, differential pressure, capacitance, optical, acoustic, and nuclear radiation attenuation. In general, the various liquid level principles apply to density measurement techniques as well. 

Head-type flowmeters include orifice plates, venturi tubes, weirs, flumes, and many others. They change the velocity or direction of the flow, creating a measurable differential pressure, or "pressure head," in the fluid. Head metering is one of the most ancient of flow detection techniques. There is evidence that the Egyptians used weirs for measurement of irrigation water flows in the days of the Pharaohs and that the Romans used orifices to meter water to households in Caesar s time. In the 18th century, Bernoulli established the basic relationship between the pressure head and velocity head, and Venturi published on the flow tube bearing his name. 

Each term on the right hand-side of Eq. (2.9) is measured independently providing a direct determination of n, also under low pressures [30]. It is necessary as well to eliminate the fluctuations in the atmospheric pressure and to measure more precisely the differential pressure pg - p, (Fig. 2.12). This is done with a sensitive draft-range differential pressure transducer from Omega (Model PX750-06DI) with an accuracy of 0.5 Pa. The capillary radius r is determined by a Kondon micrometer calliper while the surface tension of the surfactant solution - by the Wilhelmy-plate technique, and the height hc in the capillary tube - with a Wild cathetometer (Model KM-274). 

The weight of catalyst in a vessel is determined by measuring the pressure differential between taps installed at the top and bottom. Density of the fluidized catalyst is determined in a similar manner from the differential pressure between taps located a measured distance apart in the dense phase. Location of the catalyst level can be determined from the combination of the density and the total weight of catalyst, or by the use of a series of pressure taps placed at intervals along the height of the vessel. A hot-wire probe has been used to locate the level in laboratory fluidized beds (250), but this technique has not been adopted for fluid cracking units. The method depends upon the fact that heat-transfer rate from the heated wire is much higher when immersed in the dense phase of fluidized solids than when in the dilute phase. 

Differential reactor technique runs. Two series of r s have been carried out at 643 K and atmospheric pressure, by feeding 2 cmvh of a 10 wt 54 aq. 

Column differential pressure is usually measured by one of the following techniques ... 

Figure 5.8 Techniques for measuring column differential pressure, (a) Transmitter located at top (6) transmitter located at bottom (c) two transmitters (d) gas-purged system.

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