Critical capillary pressure data

Figure 10. Comparison of the critical-capillary-pressure data of Khatib, Hirasaki and Falls (5) (darkened circles) to the proposed dynamic foam stability theory (solid line). Best fitting parameters for the constant-charge electrostatic model are listed.

Comparison of the proposed dynamic stability theory for the critical capillary pressure shows acceptable agreement to experimental data on 100-/im permeability sandpacks at reservoir rates and with a commercial a-olefin sulfonate surfactant. The importance of the conjoining/disjoining pressure isotherm and its implications on surfactant formulation (i.e., chemical structure, concentration, and physical properties) is discussed in terms of the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory of classic colloid science. 

The determination of the capillary pressure of a diffusion layer is critical, not only to have a better understanding of the mass transport mechanisms inside DLs but also to improve their design. In addition, the accuracy of mafhemafical models can be increased with the use of experimental data obtained through reliable techniques. Both Gostick et al. [196] and Kumbur et al. [199] described and used the MSP method in detail to determine the capillary pressures of differenf carbon fiber paper and carbon cloth DLs as a function of the nonwetting phase saturation. Please refer to the previous subsection and these publications for more information regarding how the capillary pressures were determined. 

Figure 16. Constructing MRF data using the critical pressure gradient and capillary pressure models.

Consequently, this quantity was subtracted from the observed total pressure drop to obtain an estimate of the pressure drop associated with developed flow in the capillary. This correction is one of the most critical in the data analysis procedure and as a precaution, the high-shear experiments were designed so that this excess pressure drop was less than 10 of the total pressure drop in the system. The validity of this correction is supported by the consistency check procedure discussed below. 

Fundamental to a successful fault seal analysis is quantification of the petrophysical properties of the different fault rocks present in the hydrocarbon field under investigation. The critical properties which require quantification are permeabilities, capillary entry pressures, transmissibility, fault-rock thickness and the strength of the fault rocks. One of the reasons why fault seal analysis and reservoir modelling has proved difficult has been the absence of data on these properties. Analysis of the petrophysical properties of... 

With packed HPLC columns, conventional HPLC injectors can be used. With open capillary columns, split or splitless injection is needed in order not to overload the columns. Special injection techniques have been developed for these purposes, since standard GC techniques cannot be used at high pressures. With knowledge about the critical data of the sample solvent, a retention gap can be used to separate solvent from solutes and remove the solvent prior to solute focusing on the analytical column (Figure 5.8). 

Historically, the first experimental determinations of the vapor densities and pressures approaching the critical region of a metal were made for mercury. Bender (1915, 1918) carried out pioneering measurements of vapor densities up to about 1400 °C. The samples in these studies were enclosed in strong fused quartz capillaries. In 1932, Birch made the first measurements of the vapor pressure of mercury and obtained realistic values for the critical temperature and pressure. Birch found values = 1460 °C and = 1610 bar, results that are remarkably close to the most accurate values available today (Table 1.1). A number of groups in various countries have contributed subsequently to the pool of pVT data currently available (Hensel and Franck, 1966, 1968 Kikoin and Senchenkov, 1967 Postill et al., 1968 Schonherr et al., 1979 Yao and Endo, 1982 Hubbard and Ross, 1983 Gotzlaff, 1988). The result is that the density data for mercury are now the most extensive and detailed available for any liquid metal. Data have been obtained by means of isothermal, isobaric, or isochoric measurements, but as we have noted in Sec. 3.5, those obtained under constant volume (isochoric conditions) tend to be preferable. In Fig. 4.10 we present a selection of equation-of-state data that we believe to be the most reliable now available for fluid... 

The most critical aspect in the design of the apparatus is determining the dimensions of the capillary so that the desirable high-shear rates can be attained at moderate pressure drops to minimize the influence of viscous dissipation while maintaining the excess pressure drops associated with the entrance and exits of the capillary to below 10J of the overall pressure drop. This constraint was dictated by the data analysis procedure which is presented in the next section. 

It is obvious from Table 20 that the method of a rolling ball had been used for a long time to investigate the viscosity of Freon-21 at low pressures in the gas phase and on the saturation line. This method was criticized more than once in [1.5, 1.6]. At the same time, a sizable part of the measured values of % in Refs. [2.30, 2.38, 3.35] agree sufficiently well with each other and with the measurements made using the capillary method [2.13]. Only the data of Makita [2.32] are an exception, since they differ by 8-10%. The data on other substances obtained by the same author were also found to be as inaccurate [2.3]. 

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