Characteristics Analysis of Inhomogeneous, Nonequilibrium, Two-Phase Flows Using the Drift-Flux Model

An exact analytical solution of the characteristic equation of homogeneous nonequilibrium two-phase (gas-liquid) flow using the drift-flux model and an approximate, highly accurate, analytical solution of the characteristic equation of inhomogeneous nonequilibrium two-phase flows for practically all flow patterns are presented. Based on the nature of the eigenvalues, in analogy with single-phase flow and previous work in two-phase flows, the homogeneous and inhomogeneous nonequilibrium sound speeds have been defined. The resulting expressions for the sound speed are studied in a wide range of steam/water system parameters of interest such as pressure, degree of thermal nonequilibrium, and void fraction, from which conclusions concerning their general behavior are drawn. Good agreement is obtained between theoretical predictions of the sound speeds and various experimental data.