Structural Characteristics of Two-Phase Flows in Vertical Channels of Nuclear Power Plant Cooling Systems in the Natural Circulation Mode

This paper presents the results of an experimental study of structural characteristics of a two-phase flow with natural circulation in vertical channels. Local void fraction distributions in vertical pipes of different diameters (30 and 60 mm) at a pressure of 0.1 MPa are obtained for adiabatic air-water flow in the vertical channel of the natural circulation loop. A conductometric method is used for determining void fractions of phases. Limits of applicability of the calculations that are most often used when designing and validating safety systems of water-cooled nuclear power plants are determined by comparing the computational void fraction correlations to the experimental data. Recommendations on the selection and refinement of the computational methods for the void fraction calculations are given.

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