Application of the image analysis on the investigation of disturbance waves in vertical upward annular two-phase flow

Annular two-phase flow commonly exists in industries process, and the disturbance wave at the gas-liquid interface plays an essential role in the mass, momentum and energy exchange. Although extensive experimental and analytical approaches to properties of disturbance waves have been implemented, most of the empirical correlations constructed to predict the wave properties have defects in prediction, especially under the high-pressure conditions. In the present paper, an image analysis method by acquiring the spatiotemporal distribution of the liquid film is employed to investigate the wave properties in a 20 mm I.D. tube in the upward annular regime. Because the interfacial waves should first penetrate through the gas boundary layer before full development, the effect of the gas boundary layer cannot be ignored and is undoubtedly enhanced when pressure increases. Accordingly, new empirical correlations for wave velocity and frequency are proposed by introducing the excess liquid Reynolds number. Compared with the experimental data from the literature, the proposed equations agree well with the experimental data within the averaged relative deviation of +/- 35%, especially under high-pressure conditions.