The Structure of Disperse-Annular Two-Phase Flows in a Wide Range of Reduced Pressures

An analysis of two-phase disperse-annular flows requires verifying the intensity of droplet entrainment and deposition. Unlike conventional empirical equations, including those derived by processing large arrays of experimental data, we propose approximate physical models of entrainment and deposition of droplets. They are used to obtain semiempirical equations for calculating the liquid distribution over a channel cross-section with an accuracy to numerical coefficients whose values were found from the generalization of experimental data. The turbulent diffusion model applied in our previous works has been demonstrated to be valid for the prediction of the droplet deposition rate only in the range of high reduced pressures (above 0.45), for which fine droplets are characteristic. At moderate and low reduced pressures, the liquid deposition from the flow core onto the film is basically controlled by large droplets transported by energy-carrying turbulent vortices. The model based on this hypothesis yielded a single correlation for the fraction of liquid in the flow core at pressures below 10 MPa. This equation provides good fitting of the available experimental data on the structure of gas-liquid and single-component vapor-liquid two-phase flows and, together with the previously proposed formula for high reduced pressures, enables us to calculate the distribution of liquid in the channel section at pressures from 0.1 to 20 MPa.