Void fraction and pressure drop

In the absence of pressure drop and void fraction measurements, umf is calculated from equation 9.36 and emf can be estimated from equation 9.35. 

Bisschops et al. have investigated the hydrodynamic capacity and solids holdup in countercurrent two-phase flow in the centrifugal field, as well as the relation between the pressure drop and void fraction. Moreover, the analysis included a check as to whether the two-phase flow in the centrifugal field was homogeneous or heterogeneous. 

IV. Correlating Methods for Two-Phase Pressure Drops and Void Fractions 220... 

Pressure Drop and Void Fraction in Liquid-Gas Flow... 

Carey (51) has studied pressure drop and void fraction in different types of compact heat exchangers and has outlined the differences with plain tube geometries. Kreissig and Muller-Steinhagen (52) and Margat et al. (53) have shown that the principles of the methods developed for plain tubes can be used but need to be adapted. The main results of these studies are that the liquid holdup is significantly affected by the mass flow rate (Figure 28) the liquid holdup is underestimated by conventional correlation the two-phase flow multiplier can be estimated from a Chisholm-type correlation. 

The most reliable methods for fully developed gas/liquid flows use mechanistic models to predict flow pattern, and use different pressure drop and void fraction estimation procedures for each flow pattern. Such methods are too lengthy to include here, and are well suited to incorporation into computer programs commercial codes for gas/liquid pipeline flows are available. Some key references for mechanistic methods for flow pattern transitions and flow regime-specific pressure drop and void fraction methods include Taitel and Dukler (AIChEJ., 22,47-55 [1976]), Barnea, et al. (Int. J. Multiphase Flow, 6, 217-225 [1980]), Barnea (Int. J. Multiphase Flow, 12, 733-744 [1986]), Taitel, Barnea, and Dukler (AIChE J., 26, 345-354 [1980]), Wallis (One-dimensional Two-phase Flow, McGraw-Hill, New York, 1969), and Dukler and Hubbard (Ind. Eng. Chem. Fun-dam., 14, 337-347 [1975]). For preliminary or approximate calculations, flow pattern maps and flow regime-independent empirical correlations, are simpler and faster to use. Such methods for horizontal and vertical flows are provided in the following. 

Pressure Drop and Void Fraction in Liquid-Gas Flow A mixture of an oil and hydrogen at SOOpsia and 200°F enters a 3 in. Schedule 40 steel line. Data are ... 

Triplett et al. (1999) measured pressure drop and void fraction in minichannels with air-water adiabatic flows. They observed bubbly, churn, slug, slug-annular and annular flows as in conventional tubes, but the transitions were very different. Moreover they highlighted that the homogeneous model best predicted their pressure drop measurements for every flow conflguration except the annular one. 

Parameters of the Bingham Model from Measurements of Pressure Drops in a Line 107 Pressure Drop in Power-Law and Bingham Flow 110 Adiabatic and Isothermal Flow of a Gas in a Pipeline Isothermal Flow of a Nonideal Gas 113 Pressure Drop and Void Fraction in Liquid-Gas Flow Pressure Drop in Flow of Nitrogen and Powdered Coal 120... 

E. W. Jassim, T. A. Newell, Prediction of two-phase pressure drop and void fraction in microcharmels using probabilistic flow regime mapping, Int.J. Heat Mass Transfer, 2006, 49, 2446-2457. 

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