Article

Method for calculating the void fraction and relative length of bubbles under slug flow conditions in capillaries

Theoretical Foundations of Chemical Engineering (Impact Factor: 0.36). 44(1):86-101. DOI: 10.1134/S0040579510010112

ABSTRACT A method for calculating the void fraction and relative size of bubbles at the known flow rates of phases is constructed using
the mathematical model of a gas—liquid slug flow in capillaries that was developed earlier. The results of the calculations
are in good agreement with the experimental data of other authors. The boundedness of linear approximations such as the Armand
formula by the small values of the capillary numbers is revealed. It is shown that the void fraction depends not only on the
dynamic gas holdup, but also on the capillary number and the Weber number, as well as on the direction of the flow. It is
found that the ratio of the dynamic gas holdup to the void fraction varies from 1 to 2.5 as the capillary number increases.
A tenfold error in the experimental determination of the length of liquid slugs by a simplified procedure is revealed. A simple
calculation relationship that relates the dynamic gas holdup to the void fraction is derived from the Liu—Vandu—Krishna approximation.
The theoretical explanation of the causes of the abnormal dependence of the void fraction on the dynamic gas holdup in microchannels
with sizes of less than 100 fum is given. The specific features of a slug flow in microchannels that are caused by the disintegration
of a film into drops are explained. The developed calculation method can also be applied to liquid—liquid systems.

1 Bookmark
 · 
179 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, a set of state-of-the-art monolithic oscillators using different commercially available SiGe foundry processes, and a research process, are to be presented, Results comprise a 25 GHz oscillator, a 27 GHz VCO, and a 19 GHz VCO. All coplanar MMICs are fully monolithic
    Silicon Monolithic Integrated Circuits in RF Systems, 2001. Digest of Papers. 2001 Topical Meeting on; 02/2001
  • [Show abstract] [Hide abstract]
    ABSTRACT: The hydrodynamics of slug flow in a horizontal capillary with a diameter of 0.92 mm is experimentally studied using water-air and aqueous glycerol solution-air systems. The experimental data (the velocity of bubbles, the volume fraction of the gas, the relative length of bubbles, and the pressure drop) are compared with the results of calculation by the previously constructed mathematical model of the slug flow of a gas-liquid mixture in capillaries. The developed model is in satisfactory agreement with experimental data in the range of capillary numbers from 0.05 to 0.12.
    Theoretical Foundations of Chemical Engineering 01/2011; 45(3):235-247. · 0.36 Impact Factor