Transfer in Taylor Flow

The experimental works on investigation of gas-liquid mass transfer in microstructured reactors are listed in Table 7.4. Most of the experimental results were obtained for Taylor flow in capillaries with diameters between 1 and 3 mm. The influence of experimental conditions on mass transfer is very complex. This explains why most of the published relations describing gas-liquid mass transfer are empirical. 

Slug(Taylor) flow - vertical reactor Absorption of oxygen from air into water, ethanol, and ethylene glycol (EG) 

Slug(Taylor) flow — vertical reactor Nomeacting system Methane—water 

Slug flow, slug annular, churn flow Reacting system C02/buffer solution of 0.3MNaHCO3, 0.3 M Na2C03, NaOH 

The volumetric mass transfer of the bubble caps is obtained by multiplying the mass transfer coefficient with the specific surface of the two caps referred to the 

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Irandoust S, Andersson B. Simulation of flow and mass transfer in Taylor flow through a capillary. Computers Chem Eng 1989 13 519-526. 

S. Irandoust, S. Ertle, and B. Andersson, Gas-liquid mass transfer in taylor flow through a capillary. Can. J. Chem. Eng. 70 115 (1992). 

Mass transfer in Taylor flow is usually characterized as localized into zones of mass transfer resistance [14]. In between these zones, perfect mixing is assumed. Using this... 

S. Irandoust and B. Andersson, Simulation of Flow and Mass Transfer in Taylor Flow Through a Capillary, Computers Chem. Engng, 13(415) 5 9 (1989). 

Table 7.4 Literature on gas-liquid mass transfer in Taylor flow.

In summary, the gas-liquid mass transfer in Taylor flow has two contributions (see Figure 7.6b) (i) the caps (assumed to be hemispherical) at both ends of the bubble and (ii) the liquid film surrounding the lateral sides of the bubble. Considering these two contributions and assuming resistance in the liquid phase, the relationship for the overall mass transfer coefficient /r ) is given in the... 

W. Salman, A. Gavriilidis, P. Angeli, Axial mass transfer in Taylor flow through circular microchannels. AIChE J., 2007,53 (6), 1413-1428. 

For predicting mass transfer in Taylor flow, gas-liquid and liquid-wall mass transfer coefficients are required. Mass transfer coefficients from gas to liquid were found experimentally to be in the range 0.1-0.8 s and correlations have been... 

Taylor, R., On Multicomponent Mass Transfer in Turbulent Flow, Letts. Heat Mass Transfer, 8, 397-404 (1981b). 

Spalding DB (1980) Numerical Computation of Multi-Phase Fluid Flow and Heat Transfer. In Taylor C. et al. (eds) Recent Advances in Numerical Methods in Fluids. Pineridge Press, pp. 139-167. 

FIGURE 15.98 Bases for description of evaporative heat transfer in slug flow (from Wadekar and Kenning [246], with permission from Taylor Francis, Washington, DC. All rights reserved). 

V. V. Yagov, The Principle Mechanisms for Boiling Contribution in Flow Boiling Heat Transfer, in Convective Flow Boiling, J. C. Chen ed., pp. 175-180, Taylor Francis, Washington, DC, 1996. 

In order to overcome the coupling of power dissipation and mass transfer, we need to consider a different mechanism for gas-liquid contacting. If we turn to laminar flow, an external structure should be used to create or maintain the surface area. For example, in a falling-film reactor the gas /liquid interfacial area is roughly equal to the wall area. In capillaries at moderate velocities, the predominant flow pattern is called Taylor [29] flow, see Fig. 6.3. In Taylor flow, the gas bubbles are too large to retain their spherical shape and are stretched to fit inside the channel. Surface tension pushes the bubble towards the channel wall, and only a thin film remains between the bubble and the wall. 

J.M. van Baten, R. Krishna, CFD simulations of wall mass transfer for Taylor flow in circular capillaries, Chem. Eng. Sci., 2005, 60, 1117-1126. 

Van Baten and Krishna [41] performed a computational fluid dynamics (CFD) study of gas absorption in Taylor flow and found that in some of the experiments of Bercic and Pintar the contact time in the film was indeed long enough to saturate the liquid film fully. For shorter unit cells (or higher velocities), they formulated a mass transfer model of penetration theory for both the caps and the film... 

Figure 10.9 Gas-liquid mass transfer coefficient in Taylor flow [40].

Nijhuis et al. also carried out the hydrogenation of a-methylstyrene in both a monolith and trickle bed reactor [49]. The monolith was 10 mm in diameter with a cell density of 400 cpsi, whereas the trickle bed was 47 mm in diameter. Both reactions were carried out in the Taylor flow regime. The catalyst productivity, defined as the rate of product formation per unit volume of catalyst, was found to be 6.2 mol m s , compared with 4.6 mol m s . To test the importance of Taylor flow in the reduction of mass transfer limitation and enhancement of the observed reaction rate, the researchers also carried out a liquid-full experiment, where only liquid presaturated with hydrogen was fed to the monolith. The catalyst productivity in this case was 1.5molm s . This experiment clearly indicates that the mass transfer rate of hydrogen through the phase interface in Taylor flow is much faster than in the bulk liquid. 

Van Eaten and Krishna [91] simulated liquid-to-wall mass transfer for Taylor flow in circular capillaries of 1.5, 2.0, and 3.0 mm diameter. In their analysis, the wall mass transfer process consisted of two separate contributions (i) wall-slug contribution of the regions in contact with the liquid slug and (ii) wall-film contribution of the region in contact with the liquid film surrounding the bubble. A correlation for total liquid-to-wall mass transfer coefficient was proposed ... 

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