Slug length

A large number of studies have been conducted to predict slug length, but none of these studies have covered the full range of operations. One study was conducted in the Prudhoe Bay field in Alaska [8]. During this study. 

The value of X( depends on the pipe diameter and superficial gas velocity it is expressed by the following equation  

Estimate the slug volume for a 400 NB (ID = 406 mm), 3000 m long horizontal pipeline. The superficial gas velocity is 10 m/sec. 

Process engineering and design using Visual Basic 

Density is normally obtained from simulation, and it is used directly. Sometimes a two-liquid phase is separated as a single phase, and the density of the mixed liquid is calculated as 

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Note that the average void fraction of a slug unit depends only on the liquid and gas flow rates, the dispersed velocity ub, the translational velocity w, and the void fraction within the liquid slug, a, and it is independent of the bubble shape or bubble length, the liquid slug length, as well as the film thickness in the film zone (Barnea, 1990). 

The main slug body—The length of this zone is (ls — /m), where /s represents the slug length. The slug moves as a fully developed, homogeneous mixture. 

At low liquid rates, the onset of instability occurs at a constant value of the total superficial velocity, and is predictable from holdup and flooding data for wetted wall columns. As liquid flow rates increase, Nicklin and Davidson predict that unstable flow begins at lower values of the gas flow rate. For high liquid flow rates, however, the slug length becomes important, and the unstable flow will begin at higher values of gas flow rate. Therefore, a definite liquid flow rate exists at which an unstable flow pattern appears with a minimum gas flow rate. 

The resistance to mass transfer within a slug in a liquid of low viscosity has been measured by Filla et ai (F5), who found that kA) was approximately proportional to the square root of the diffusivity within the bubble, p, as predicted by the thin concentration boundary layer approximation. In addition, kA JA was independent of slug length for 1 < L/D < 2.5. 

Z. Taylor bubbles in single capillaries (square or circular) < (m Applicable j > 3s-0-5 [E] Air-water Luc = unit cell length, Lsiug = slug length, dc = capillary i.d. For most data kLa + 20%. [153]... 

Since the residence time in cocurrent downflow is very short, it is necessary to recirculate the liquid and the gas. Also, the best performance from a mass transfer point of view is when the gas and liquid volume flow rates are about equal, and with a bubble/slug length of about O.S-2 cm. In these cases the molar flow of gas is much less than that of liquid, and the gas component will be consumed before the liquid component reaches complete conversion. Without recirculation, new gas must be added to the liquid further down in the reactor. 

The analysis of power input and mass transfer in this chapter was Umited to scaling, and the results serve to demonstrate the opportunities that arise when alternatives to the contacting workhorse, turbulence, are considered. The works of BerCiC and Pintar [32] and Van Baten and Krishna [2] have elucidated the most important aspects of G/L mass transfer, and two-phase pressure drop in capillary channels is discussed in detail by Kreutzer et al. [1], but more experimental mass-transfer data is needed, in particular with using different fluids at controlled, independently varied bubble and slug lengths. 

Berfif, G. Pintar, A., The role of gas bubbles and liquid slug lengths on mass transport in the Taylor flow through capillaries. Chem. Eng. Sci. 1997, 52 (21/22), 3709-3719. 

Bercic, G., Pintar, A. (1997). The role of gas bubbles and liquid slug lengths on mass transport in the Taylor flow through capillaries. Chemical Engineering Science, 52, 3709—3719. Beretta, A., Ferrari, P., Galbiati, L., Andreini, P. (1997). Horizontal oil-water flow in small diameter tubes. Flow patterns. International Communications in Heat and Mass Transfer, 24, 223-229. 

Liu, H., Vandu, C. O., Krishna, R. (2005). Hydrodynamics of Taylm flow in vertical capillaries flow regimes, bubble rise velocity, liquid slug length, and pressure drop. Industrial and Engineering Chemistry Research, 44, 4884-4897. 

To maintain the total volume of the slug as constant, the instantaneous slug length, i.e., L(9i, 62) is determined by the initial slug length Ls and the static contact angle 9 as... 

Kreutzer [11] suggested a correlation for the slug length, L, based on experimental data in a 200 cpsi monolith reactor ... 

Bubble and slug lengths can be obtained by multiplying Eq. 10 with the respective phase volume firactions. 

Amador C, Salman W, Sanguanpiyapan S, Gavriilidis A, Angeli P (2004) Effect of gas/liquid inlet conditions on slug length in Taylor flow. In Proceedings 5th international conference on multiphase flow (CD-ROM), Japan... 

Figure 7.6 Experimental snapshots and schematic presentation of Taylor flow in different configurations, (a) Taylor flow in vertical capillary, (b) Schematic presentation of Taylor flow in horizontal capillary (Ej, - length of bubble and - unit slug length). (Adapted with permission from...

On the basis of the experimental studies of Taylor flow in capillaries of Heiszwolf et al. [48], an empirical correlation for estimating liquid slug lengths (ijiug) proposed by Kreutzer [30] ... 

Slug length and length of a unit cell (Equation 7.25) ... 

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